BSNL Training report


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Company Profile



Bharat Sanchar Nigam Limited

Bharat Sanchar Nigam Limited (Bsnl) Is India'S Leading Telecommunications Provider And The Country'S Largest Public-Sector Firm. Bsnl Provides Local-Exchange Access And Domestic Long-Distance Services Through A Network Of More Than 45 Million Access Lines Covering Most Of India. It Also Offers Wireless Communications, Data And Internet Services, As Well As Business Voice And Data Services. The Company Is Still Controlled By The Government, As Is One Of India'S Other Large Phone Companies, Mahanagar Telephone Nigam Limited (Mtnl). Plans To Merge The Two Companies Have Been Discussed But Seem To Be On Hold.

Highlights

Bharat Sanchar Nigam Limited Has A Vast Reservoir Of Highly Skilled And
Experienced Work Force Of About 3,57,000 Personnel.

We Believe That Our Staff, Which Is One Of The Best Trained Manpower In The
Telecom Sector, Is Our Biggest Asset.

To Meet The Technological Challenges, Employees Are Trained For Technology
Up-Gradation, Modernization, Computerization Etc In Bsnl'S Training Centers
Spread Across Country.

To Apex Training Centers Of Bsnl I.E. Advance Level Telecom Trainingcenter
(Alttc) At Ghaziabad And Bharat Ratna Bhimrao Telecom Training Center
At Jabalpur Are Comparable To Any World Class Telecom Training Center.
Moreover, 43 Zonal Training Centers And A National Academy Of Telecom
Finance And Management Have Been Running For Several Years Now.

Different Curriculum Run In These Centers To Impart Technology Based Training,
Training For Attitudinal Change, Basic Educational And Skill Development
Program Etc.








Particulars Of The Organisation
Date Of Incorporation Incorporated On 15.9.2000, Vide Registration No. 55-107739, Dated The 15Th September, 2000 And Became Entitled To Commence Business With Effect From 19Th September, 2000.

The Company (Bsnl) Took Over The .Business Of Providing Telecom Services And Network Management Throughout The Country Except The Metro Cities Of Delhi And Mumbai Of The Erstwhile Service Providing Departments Of The Govt. Of India, I.E., The Departments Of Telecom Services And Telecom Operations W.E.F. 1.10.2000 Pursuant To An Mou Signed Between The Bsnl And The Govt. Of India.
Type Of Company Government Company Under Section 617 Of The Companies Act, 1956.
Administrative Ministry Govt. Of India, Ministry Of Communication And Information Technology, Department Of Telecommunications.
Details Of Disinvestments The Entire Share Capital Of The Company Is Held By The Govt. Of India
Shareholding Pattern Government Of India Is Holding 100% Of The Share Capital Of The Company
Listing With Stock Exchanges Not Applicable, As The Bsnl Is An Unlisted Company
Share Capital Authorised Capital – Rs.17,500 Crores, Divided Into 1,000,00,00,000[One Thousand Crores] Equity Shares Of Rs.10/- Each; And 750,00,00,000 [Seven Hundred And Fifty Crores] Preference Shares Of Rs.10/- Each
Paid Up Share Capital - Rs.5,000/- Crores Of Equity Shares And Rs.7,500/- Crores Of Preference Share Capital






Vision

To Become The Largest Telecom Service Provider In South East Asia.

Mission

- To Provide World Class State-Of-Art Technology Telecom Services On Demand At
Affordable Price.

- To Provide World Class Telecom Infrastructure To Develop Country'S Economy.

Profile Of The Company’S Business

A. Glimpses Of Main Services Offered

1. Basic And Limited Mobile Telephone Services
Bsnl Is The Leading Service Provider In The Country In The Basic Telephone Services. As Of Now More Than 35 Million Direct Exchange Lines & More Than 2.2.Million Telephones In The Limited Mobile Telephone Services Are Existing. Bsnl Has Provides A Number Of Attractive Tariff Packages & Plans Which Shall Further Strengthen Its Subscriber Base.

2. Cellular Mobile Telephone Services
Bsnl’S Gsm Technology Based Cellular Mobile Network Has Reached A Long Way, Covering More Than 6400 Towns, With A Subscriber Base Of Over 1.54 Crore As On 31St Jan. 2006 Out Of Which 1.16 Crore Cellular Telephones Are In The Prepaid Segment.

3. Internet Services
Bsnl Offers Dialup Internet Services To The Customers By Post-Paid Service With The Brand Name ‘Netone’, And Pre-Paid Service With The Brand Name ‘Sancharnet’. The Post-Paid Service Is A Cli Based Access Service, Currently Operational In 100 Cities. Sancharnet Is Available On Local Call Basis Throughout India To Isdn And Pstn Subscribers. The Internet Dhaba Scheme Of The Company Aims To Further Promote Internet Usage In Rural And Semi Urban Areas.
To Keep Pace With The Latest And Varied Value Added Services To Its Customers, Bsnl Uses Ip/Mpls Based Core To Offer World Class Ip Vpn Services. Mpls Based Vpns Is A Very Useful Service For Corporates, As It Reduces The Cost Involved As Well As The Complexity In Setting Up Vpns For Customers Networking. As On 31.03.2005, Your Company’S Total Internet Customer Base Was 17,98,089 And Total Internet Dhabas Were 4143. A Total Of 708594 Dial Up Internet Connections Have Been Given During 2004-2005, Against A Target Of 7 Lakhs. Bsnl Plans To Give 1215980 More Dial Up Connections During The Year 2005-06. As On 31.1.2006, There Were 2367404 Internet Subscribers Working In Bsnl Net Work.


4. Intelligent Network

Intelligent Network Services Is A Service That Incorporates Several Value Added Facilities, Thoroughly Designed To Save Time And Money, And Enhance Productivity. At Present, Your Company Offers Free Phone (Fph), Premium Rate Service (Prm), India Telephone Card (Itc), Account Card Calling (Acc), Virtual Private Network (Vpn), Universal Access Number (Uan) And Tele Voting In Services. With The Commissioning Of Five Numbers Of New Technology In Platforms (Four General Purpose And One Mass Calling) At Kolkata, Bangalore, Ahmedabad And Hyderabad, The India Telephone Card Facility And New Value Added Services Are Being Provided Throughout The Country. Activation Of These New In Platforms Had Increased The Sale Of Itc Cards Taking The Figure To Rs.265 Crores In 2004-05 Alone.

5. Broadband Services

Bsnl Has Launched Its Broadband Services Under The Brand Name ‘Dataone’ On 14/1/2005. This Offers Services Like High Speed Internet Access With Speed Ranging From 256 Kbps To 8 Mbps. Other Services Like Streaming Video, Video On Demand, Bandwidth On Demand Etc., Have Also Been Planned. As On 31.12.2005 , There Were More Than 356000 Broad Band Connection Provided By The Bsnl. There Are Plans To Give 2 Million And 3 Million Connections In 2006 And 2007 Respectively.

B.Development Of Rural Telecom Network

1. Rural Dels

As On 31.03.2005, In Bsnl’S Network, A Total Of 1.356 Crore Rural Telephone Connections Were Working. As On 31.1.2006, There Are 1.425 Crore Rural Telephones Working In Bsnl Network.

2.(A)Village Public Telephones (Vpts) & Rcps:-

Bsnl, In Its Unstinted Efforts To Make The Slogan ‘Connecting India’, A Reality, Had Provided Vpts In 5,18,992 Villages Up To 31.03.2005. The Company Entered Into An Agreement With Uso Fund For Expansion Of Rural Telecom Network By November 2007, By Providing Vpts In 66,822 Undisputed, Undisturbed, Accessible And Inhabited Villages Having Population More Than 100 As Per Census, 1991 In The Country. Bsnl Provided Vpts In 5,28,886 Villages Up To 31.01.2006. There Are Plans To Replace All Marr Vpts In The Country . As Of Now Total 123194 Marr Vpts Already Replaced In The Country By Bsnl. Bsnl Also Committed To Provide The Rural Community Phones As Per The Uso Fund Agreement. As Of Now Around 13713 Rcps Already Provided By Bsnl.

2(B) Public Telephones:-

There Are More Than 2 Million Pcos Working In The Bsnl Network Out Of Which Around 1 Million Pcos Are Having Std/Isd.

C. Network Management
Bsnl Is Committed To Provide A Robust State Of The Art Infrastructure That Will Provide Stable And Superior Services To Its Customers. Accordingly, The Mlln Network Covering More Than 200 Cities Was Made Operational In May 2004. Since Then, About 22000 Circuits Have Been Provided On This Network. This Has Provided High Level Of Stability To The Leased Circuits And Capability To Offer N X 64 Kbps Circuits. Keeping In View The Growing Demand Of Leased Circuits, The Network Is Being Expanded To Cover About 50 More Locations And Additional Capacity At Many Existing Locations Is Also Being Provided.

To Improve The Operational Efficiency Of Ccs 7 Signaling, Stand-Alone Signaling Transfer Point (Sstp) Equipment Is Being Procured. This Will Also Enable The Company To Measure Signaling Traffic Of Other Operators, Who Are Using Its Signaling Network For Exchanging Messages, Specially With Regard To Cellular Services. Bsnl Has More Than 4.7 Lakhs Route Kilometers Of Optical Fibre Network In The Country & Has Installed Capacity More Than 6.4 Million Lines For The Tax Meant For The Std/Isd Network.


D. Setting Up Ku Band Vsat Network
As Regards The Ku Band Vsat Network Equipment, The Hub Of This Network Is Being Set Up At Bangalore, The Equipment Has Been Installed And Expected To Be Commissioned Shortly. This Will Help Your Company, To Become A Service Provider With All Types Of Media Equipment I.E. Ofc, Microwave And Satellite For Provision Of Bandwidth, This Will Also Enable The Company To Offer Composite Solutions To Its Customers.

E. Policy On Transmission Network Maintenance
Telecom Circles Have Large Transmission Networks. To Improve The Maintenance Of Transmission Network, Guidelines For Route Parties And Vehicles Have Been Formalised. Telecom Territorial Circles Are Also Being Connected With Computerised Network For Booking Of Transmission System Faults, With A View To Improve Follow Up And Faster Restoration Of Faults.

F. Annual Maintenance Contracts For Switching System & Wll
Comprehensive Amc, Which Includes Hardware And Software Maintenance And Upgrade, Has Been Arranged With The Respective Equipment Suppliers. Initial Feedback Suggests That, As A Result Of Preventive And Corrective Maintenance Support, The Performance Of Switches Is Improving. Difficulties In Entering Into Amc With Rural Wll Equipments Suppliers Have Been Resolved And Procedures Streamlined So That Adequate Maintenance Support Becomes Available. As A Result, The Performance Of Wll Network Is Improving. Amc Arrangements Have Also Been Made With Suppliers Of Fwts And Hand Held Terminals.
G. Computerisation
Implementation Of Inter Operator Billing And Accounting System (Iobas) Has Been Completed. Your Company Plans To Provide Cdr Based Customer Care And Convergent Billing System. This Will Help Company In Providing Effective And Efficient Billing & Customer Care Solutions For Its Fixed Line Subscribers. It Envisages Building Of Country Wide Intranet To Reduce The Cost Of Operation, Increase Realization, Stop Leakage Of Revenue And Minimize Frauds, Besides Providing Round The Clock Best Customer Care Services To The Company’S Subscribers.

Call Center Facility Has Been Introduced For 71 Ssas, Which Is A Single Point Approach For Addressing All Customer Needs Cum Grievances. Web Based Public Grievance Management System Has Been Implemented For Speedy Disposal And Monitoring Of Public Grievances. Web Based Inventory Management Package Has Also Been Introduced, Through Which, Material Management Functions Are Being Computerized Gradually In Different Circles. Online Mobile Bill Viewing Facility Has Been Made Available To All Cell One Mobile Customers (All States) Through Company’S Portal (Http://Bsnl.In). Duplicate Telephone Bill Viewing Facility For Landline Telephone Has Also Been Made Available At Many Places Through Websites Of Respective Telecom Circles.

H. Obligations

1. Towards Customers And Dealers
To Provide Prompt, Courteous And Efficient Service And Quality Of Products/Services At Fair And Reasonable Services.
2. Towards Employees
? Develop Their Capability And Advancement Through Appropriate Training And Career Planning
? Expeditious Redressed Of Grievances
? Fair Dealings With Recognized Representatives Of Employees In Pursuance Of Healthy Trade Union Practices And Sound Personnel Policies






3. Towards The Society –Corporate Social Responsibilities
Corporate Social Responsibilities
Bsnl Is Committed To Provide Quality Telecom Services At Affordable Price To The Citizens Of The Remotest Part Of The Country. Bsnl Is Making All Effort To Ensure That The Main Objectives Of The New Telecom Policy 1999 (Salient Points Indicated Below) Are Achieved:
Access To Telecommunications Is Of Utmost Importance For Achievement Of The Country'S Social And Economic Goals. Availability Of Affordable And Effective Communications For The Citizens Is At The Core Of The Vision And Goal Of The New Telecom Policy 1999.
Strive To Provide A Balance Between The Provision Of Universal Service To All Uncovered Areas, Including The Rural Areas, And The Provision Of High-Level Services Capable Of Meeting The Needs Of The Country'S Economy Encourage Development Of Telecommunication Facilities In Remote, Hilly And Tribal Areas Of The Country;
Transform In A Time Bound Manner, The Telecommunications Sector To A Greater Competitive Environment In Both Urban And Rural Areas Providing Equal Opportunities And Level Playing Field For All Players
I. Assistance During Natural Calamities

Bsnl Always Remains Awake Of Its Responsibility As A Corporate Citizen. When The Destructive Tsunami Waves Struck The Indian Shores, Bsnl Company Swung Into Action Immediately For Providing Relief To Those Affected In The Coastal Areas. Communication Networks At The Coastal Areas Of Tamil Nadu, Kerala And The Andaman And Nicobar Islands – Worst Hit In The Tsunami - Were Promptly Restored Within The Shortest Possible Time. Bsnl Along With The Employees Contributed An Amount Of Rs. 2,207 Lakhs To The Prime Minister’S Relief Fund. Telephone Services Were Restored In Record Time In The Flood-Hit Areas Of Gujarat And Maharashtra.








Ocb 283

Introduction

Telecommunication Networks Are Constantly Changing. The Rapid Growth Of The Digital Network, Mobile Network And Intelligent Network And The Proliferation Of New Services Being Constantly Offered To Subscriber Means That Equipment Must Be Continuously Adapted To New Requirements. All The New Switching Systems Are Based On Stored Program Control Concept. The Call Processing Programmes Are Distributed Over Different Control Organs Of The System And Are Stored In Rom/Ram Of The Units Processor In The Control Units By Using The Programme And Data Stored In Unit Rom/Ram Process And Handle Calls. Handling Or Processing A Call Means To Ultimately Establish A Connection In Between Incoming And Outgoing Ends. Depending On The System The Name And Architecture Of Control Units And Switch May Change But Basic Criterion For Switching More Or Less Remains Same.
The Alcatel 1000E10 Exchange Also Known By Its Other Name Ocb283 Is Designed To Cater For Evolving Networks And The Need To Rationalize Equipment Operation. Its Modular Architecture Means That New Services Can Be Added And Processing Capacity Can Be Increased Without Interrupting Operation Of The Exchange. Ocb 283 Is A Digital Switching System Which Supports A Variety Of Communication Needs Like Basic Telephony, Isdn, Interface To Mobile Communication, Data Communication Etc. This System Has Been Developed By Alcatel Of France And Therefore Has Many Similarities To Its Predecessor E-10. The First Ocb283 Exchange Of R11 Version Came To India In 1993. At Present R23 And R24 Are Also Being Supplied. The Basic Architecture Remaining Same, More Facilities To Subscriber And Administration Are Supported By Later Versions.

Features Of The System

I. It Is A Digital Switching System With Single ‘T’ Stage Switch. A Maximum Of 2048 Pcms Can Be Connected.

Ii. It Supports Both Analogue And Digital Subscriber.

Iii. The System Supports All The Existing Signaling System Like Decadic, Mf, Cas And Also Ccitt#7 Signaling System.

Iv. It Provides Telephony, Isdn, Data Communication, Cellular Radio And Other Value Added Services.
V. The System Has ‘Auto Recovery’ Feature. When A Serious Fault Occur In A Control Unit, It Gives A Message To Smm(Operation & Maintenance Unit). The Smm Puts This Unit Out Of Service, Loads The Software Of Faulty Unit In A Backup Unit And Bring It Into Service. Diagnostic Programmes Are Run On The Faulty System And Diagnostics Are Printed On The Terminal.

Vi. Ocb283 Has Double Remoting Facility. Subscriber Access Unit Csnd Can Be Placed At A Remote Place And Connected To The Main Exchange Through Pcm Links. Further Line Concentrators Are Placed At A Remote Location And Connected To The Csnl Or Csnd Through Pcms. This Special Feature Can Meet Entire Range Of Necessities Like Urban, Semi-Urban And Rural.

Vii. Various Units Of Ocb283 System Are Connected Over Token Rings. This Enables Fast Exchange Of Information And Avoid Complicated Links And Wiring Between Various Units.

Viii. The Charge Accounts Of The Subscribers Are Automatically Saved On The Disc, Once In A Day. This Avoids Loss Of Revenue In Case Of Total Power Supply/ Battery Failure Or Any Other Type Of Exchange Failure.

Ix. Traffic Handling Capacity Of The System Is Very Huge. It Can Handle 8,00,000 Bhca And 25,000 Erlangs Of Traffic. Depending On The Traffic, A Maximum Of 2,00,000 Subscribers Or 60,000 Circuits Can Be Connected.

X. The Exchange Can Be Managed Either Locally Or Through Nmc Of 64Kbps Link.

Xi. The Ocb283 System Is Made Up Of Only 35 Different Type Of Cards. This Excludes Cards Required For Csn. Because Of This The Number Of Spare Cards Required For Maintenance Purpose, Are Drastically Reduced.

Xii. All The Control Units Are Implemented Are Implemented On The Same Type Of Hardware. This Is Called A Station. Depending On The Requirement Of Processing Capacity, Software Of Either One Or Several Control Units Can Be Located On The Same Station. For All These Control Units, Only One Backup Station Is Provided, Enabling ‘Automatic Recovery’ In Case Of Fault.

Xiii. The System Has Very Modular Structure. The Expansion Can Be Carried Out Very Easily By Adding Necessary Hardware & Software.
Xiv. The Smm(O&M Units) Are Duplicated, With One Active And Other Hot Standby. In Case Of Faults, The Switchover Takes Place Automatically. Moreover, Discs Are Also Connected To Both The Smms, There Is No Necessity Of Changing Of Cables From One To Another.

Xv. The Hard Disc Is Very Small In Size, Compact And Maintenance Free. It Has A Very Huge Memory Capacity Of 1.2Gb. The Detail Billing Data Are Regularly Saved In These Discs Itself, From There It Can Be Transferred To The Magnetic Tapes For The Purpose Of Processing.

Xvi. There Is No Fixed Rack And Rigid Suite Configuration In This System. It Provides Greater Flexibility And Adjustment In The Available Space.

Xvii. This System Can Work At A Temperature 5°C To 45°C, Though The Optimum Temperature To Work Is 22°C.




Subscriber Facilities Provided By Ocb283

It Provides A Large Number Of Subscriber Facilities. Some Facilities Are Available To Only Digital Subscriber And As Such They Can Not Be Availed By Analogue Subscribers. To Avail These Facilities Subscriber Number Are Given Special Categories By Man Machine Commands.
I. A Line Can Be Made Only Outgoing And Incoming.

Ii. Immediate Hotline Facility – The Subscriber Is Connected To Another Predetermined Subscriber On Lifting The Handset, Without Dialing Any Number.

Iii. Delay Hotline Facility – When Subscriber Lifts The Handset, Dial Tone Is Provided, He Can Dial Any Number. If He Does Not Dial A Number, Within A Predetermined Time, He Is Connected To Predetermined Number.

Iv. Abbreviated Dialing – The Subscriber Can Record A Short Code And Its Corresponding Full Number In The Memory. Later To Dial This Number He Has To Dial Only Short Code Of That Number.

V. Call Waiting Indication – When A Subscriber Is Engaged In Conversation And If Getting An Incoming Call, An Indication Is Given In The Form Of A Tone. Hearing This, The Subscriber Has Option, Either To Hold The Subscriber In Conversation And Attend The Waiting Call Or To Disconnect This Subscriber And Attend To The Waiting Call. In The Former Case He Can Revert Back To The Earlier Subscriber.

Vi. Call Forwarding – When Provided, Incoming Calls To The Subscriber Gets Transferred To The Number Mentioned By The Subscriber While Activating The Facility. This Facility Is Especially Very Useful For Those Person Who Are Always On Move.

Vii. Conference Between 4 Subscribers – The Subscriber A & B While In Conversation, Can Include Two More Subscriber By Pressing ‘* Button’ And Dialing Their Numbers.

Viii. Automatic Call Back On Busy – If This Facility Is Activated And If The Called Subscriber Is Found Busy, The Calling Subscriber Simply Replaces The Receiver. The System Keeps Watch On The Called Subscriber And When It Becomes Free, A Ring Is Given To Both The Subscribers. On Lifting They Can Talk To Each Other.

Ix. Priority Lines – Calls From These Lines Are Processed And Put Through Even When The Number Of Free Channels Are Within A Threshold Or When The System Is Operating In Catastrophic Mode.

X. Malicious Call Identification – When This Category Is Given To A Subscriber, The Number Of Calling Subscriber, The Number Of Calling Subscriber To This Number Is Printed On The Terminal Or Displayed On The Caller Identification Instrument.

Xi. 12 Or 16Khz Meter Pulses – The System Can Send 12 Or 16Khz Meter Pulses On The Subscriber Line For The Operating Of The Home Meter.

Xii. Battery Reversal – The System Extends Battery Reversal When Called Subscriber Answers. This Is Useful In Case Of Ccbs( Coin Collection Box ).

Xiii. Detailed Billing – The System Provides Detail Bills Given Details Of Date, Time, Metered Units Etc.

Xiv. Absent Subscriber Service – When Activated, The Incoming Calls Are Diverted To Absent Subscriber Service For Suitable Instruction Or Information.
Xv. It Provides 64 Kb/S Digital Connectivity Between Two Subscribers For Data Communication.

Xvi. This System Provides Facsimile (Fax) Services And Videotext Services Also.

Xvii. This System Also Provides The Facility For Restriction Of The Display Of Calling Subscriber Number On Called Subscriber’S Telephone Terminal Or Caller Id Set. To Avail This Facility The Subscriber Has To Be Given A Category Like Some Vvips Or Some Beurocrats.

Xviii. User To User Signaling – The System Permits Of Mini Messages Between Calling And Called Subscribers During Call Setup And Ringing Phase.

Xix. Terminal Portability During The Call – A Subscriber (Calling Subscriber As Well As Called Subscriber) Can Unplug Telephone Instrument, Carry It To Some Other Place Or Room And Resume The Call Within 3 Minutes

Xx. Listing Of Unanswered Calls – The Number Of Calling Subscribers, Who Calls During The Absence Of Called Subscriber, Are Recorded In Called Subscriber’S Terminal. The Called Subscriber Than Check Up These Numbers And Call Them Back, If He So Wishes.

Xxi. This System Provides Two Type Of Isdn Connections To The Digital Subscriber, One Is Of 2 B + D Line (2 Voice Channels Of 64Kbps & I Data Channel Of 16Kbps) Type And Other Is Of 30 B + D Line (30 Voice Channels Of 64Kbps & 1 Data Channel Of 16Kbps) Type.














Common Channel Signaling No. 7 (Ccs#7)

Introduction

The Latest Signaling Now Being Implemented Worldwide Is Common Channel Signaling Or Also Called Ccs#7 Signaling. This Type Of Signaling Is Essential For The Setting Up Of The Isdn (Intelligent Services Digital Networks) Services.
In This Type Of Signaling The Signaling Information Is Sent From One Exchange To Other Exchange (Called Signaling Points Sp) In The Form Of Messages Coded In Binary Form, Which Is Understandable By The Intelligent Devices Available At Both The Ends Means In Both The Exchanges. The Ccitt (Consultative Committee On International Telecom Treaty) Organization Has Recommended A Standard Protocol Called Ccitt#7 Signaling. The Signaling Message Travels Over A Single Time Slot Of The Pcm Connecting The Two Exchange (Signaling Point Sp). This Time Slot Is Called Common Channel For Signaling, Hence The Name Common Channel Signaling. The Message Over This Common Channel Carry All Relevant Data For Any Of The Other Time Slots Or Circuits Which Carry Voice Or Subscriber Data. The Channels For Subscriber Are Called Voice Channels.

Common Channel Signaling

Voice Channels







Common Channel
For Signaling
.




Signaling Points





The Ocb283 Exchange Uses Common Channel Signaling Between Its Csn & The Common Control Equipment Also. Signaling Is Often Referred To As Glue, Which Holds A Network Together. It Provides The Ability To Transfer Information Between Subscribers, Within Networks & Between Subscribers And Networks. Signaling Is The Lifeblood, The Vitalizing Influence Of Telecommunication Networks. Without Signaling, Networks Are Inert. By Providing Effective Signaling System, A Network Is Transformed Into A Tremendously Powerful Medium Through Which Subscriber Can Communicate With Each Other Using A Range Of Telecommunication Services. Old Signaling System That Was Simple Mechanisms For Transferring Basic Information Are Being Replaced By Efficient Data Transfer Highways. It Is Signaling That Provides The Ability For Subscriber To Indicate To The Exchange That A Call Is Required. It Also Allows The Called Subscriber To Be Identified E.B. By Transferring The Telephone Number Dialed By Calling Subscriber.

It Allows The Transfer Of Information Between Exchanges In The Network To Establish And Release The Call. It Transforms The Foundation Of Network Into An Active Entity That Can Provide The Required Services To The Subscribers. It Consists Of The Instructions, Which Originate From The Telephone User On The Form Of Lifting The Handset In Order To Make A Call, The Transmission Of Dial Pulses Generated By Operating A Dial & Replacing A Receiver At The End Of The Call. Instructions Are Also Signaled By Exchange In The Form Of Dial Tone, Ringing Tone Etc., To Indicate The Progress Of The Call. In Addition Inter Exchange Signaling Takes Place Between A Call Is Set-Up, To Control Exchange Operations & & Check On Circuit Availability.

Types Of Signaling

Telephony Started With The Invention Of Magneto Telephones, Which Uses A Magnet To Generate The Ringing Current, The Only Signal Sent Over A Dedicated Time Between Two Subscribers. As The Switching Technology Has Undergone A Vast Change From Manual Switching To Digital Switching, The Inter Exchange Signaling Techniques Have Also Progressively Changed From Loop No Loop Signaling To Mf Signaling & Finally Digital Signaling. The First Digital Switching Developed Was Channel Associated Signaling In Which The Signaling Information Is Conveyed On A Separate Channel, Which Is Rigidly Associated Channel. The Utilization Of Such A Dedicated Channel For Each Speech Channel Is Highly Inefficient, As It Remains Idle During The Entire Speech Phase. Hence A New Signaling System Was Developed Which Is Capable Of Providing All New Services & Its Internationally Standardized Is Known As Common Channel Signaling.

Signaling In Pulse Code Modulation

Pulse Code Modulation (Pcm) Is A Method Of Converting Information From An Analog Form To A Digital Form For Transfer Over A Digital Transmission Systems, The Technique Involves Sampling The Analogue Waveform And Coded The Result In The Digital Format. Successive Sampling Allows The Analogue Waveform To Be Represented By A Series Of 8-Bit Code. 8 Bit Codes Form Numerous Speech Channels Are Assembled Into Blocks For Transmission By Inserting Into Time Slots. The Technique Is Called Time Division Multiplexing (Tdm).

The Bandwidth Required To Transmit Signal Is Much Less Than That For Speech, So That Signaling For Several Speech Channels In A Pcm System Can Be Handled By A Small Portion Of The Bandwidth. The Signaling Capacity Can Be Used For Cas Or Ccs, The Means Of Identifying To Which Speech Channel A Particular Signal Refers Is To Divide The Signaling Capacity Into Dedicated Bit Locations. Signal Pertinent To A Particular Speech Path Are Always Transmitted In Signaling Bit Locations Dedicated To That Speech Channel. The Means Of Conveying Ccs Is To Compound The Signaling Capacity Into A Signaling Channel That Is Available As And When Required.

The Ccitt Has Defined Pcm Standards For 30 Channel And 24 Channel Systems. The Capacity Available For Signaling In These Two Standards Is Different As A Result Of Differing Constraints Applied By The Pcm Standard.

In 30 Channel Pcm Systems, The 8-Bit Code Relating To 30 Speech Channels Are Time Divisioned Multiplexed Into A Frame. Each 8-Bit Code Is Inserted Into A Time Slot Within The Frame. Time Slot 0 Is Used For Alignment; Time Slots 1-15 And 17-31 Are Used For Encoded Speech Related To 30 Channels. The Slot 16 Is Dedicated For The Use Of Signaling.

The Tenet Of Cas System Is That Dedicated Signaling Capacity Is Available For Each Speech Circuit. This Is Achieved In 30 Channel Pcm Systems By Allocating 4 Bits In Each 16-Frame Multi-Frame To Signaling For Each Speech Channel.




Frame
Multi-Frame
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


Speech Channel
Time Slot
Frame
- 1 2 3 15 - 17 28 29 30
0
1 2 3 15 16 17 29 30 31



Bits
1 2 3 4 5 6 7 8

Fig. : Frame Structure Of 30-Channel Pcm System

Principle Of Ccs
In Common Channel Signaling Systems, The Physical Tie Between The Signaling Path And Traffic Circuit Is Removed. All Signaling Transfer Relating To A Transmission Link Takes Place Over A Dedicated Signaling Channel. Hence, A Common Signaling Channel Handles The Transfer Of Signaling Information For Numerous Traffic Circuits. Signaling Capacity Is Not Reserved For Each Circuit, But Signaling Capacity Is Allocated Dynamically As When Required. Fig. Shows The Concept Of Ccs For Both Access And Inter-Exchange Signaling. Exchange A And B Are Connected By Numerous Speech Circuits, Denoted By Solid Lines. All The Signaling That Relates To The Speech Circuit Is Transferred Between The Exchanges Using The Common Signaling Path (Denoted By Dotted Lines). The Common Signaling Path Can Be Regarded As A Pipe Between Two Exchanges, Typically Operating At 64 Kbps, Into Which All Signaling Information Is Funneled. Similarly, All Signaling Information Pertaining To The Speech Circuit Between Each Subscriber And Exchange A Is Transferred Via The Access-Signaling Channel.





Speech





Fig. : Ccs Signaling : Associated Mode Of Operation



The Transfer Of Signaling Information Is Achieved By Sending Message Down The Common-Signaling Path. The Use Of Message In Ccs Systems Opens Up A Whole Range Of Flexibility That Is Not Present In A Cas System. Instead Of Being Limited To A Small Number Of Meanings For Signals Messages Can Be Designed To Cover Multitude Of Situations And Services.

The Signaling Activity When Setting Up & Releasing A Circuit Is High; However On An Average The Signaling Activity For A Circuit Is Low Because There Are No Signaling When The Calls Are Not Being Made & During The Conversation Phase Of The Call. Hence, A Single Ccs Channel Can Be Used To Use Numerous Traffic Circuits. The Theoretical Limit Of The Number Of Traffic Circuits Handled By Ccs Channel Is Very High, But A Typical Practical Value Is 2000Traffic Circuits. The Picture Become More Complex When Non-Circuit Related Signaling Activity Is Taken Into Account. Non Circuit Related Signaling Can Be Intermittent (E.G. It Is Used During Call Establishment To Interrogate A Database) Or It Can Exhibit A High Signaling Activity (E.G. If It Is Used To Transfer A Large Amount Of Management Data Between Nodes In A Network).

Mode Of Operation

Ccs System Can Operate In A Number Of Modes With In Telecommunication Network. An Exchange In Telecomm Network That Operates Ccs Is Termed As A ‘Signaling Point’. Any Two Signaling Points With The Possibility Of Signaling Communication Are Said To Have ‘Signaling Relation’. The Realization Of The Signaling Relation Is By Sending Signaling Messages Between The Two Exchanges. The Path Taken By The Signaling Messages Is Determined By The Mode Of Operation. Hence The Modes Of Operation Determine Hoe Signaling Messages Routed Between Signaling Points. The Modes Of Operation Can Be ‘Associated’, ‘Non-Associated’, Or ‘Quasi-Associated’.

In The Associated Mode Of Operation, The Signaling Messages Transferred Over Transmission Link Directly Connecting The Relevant Signaling Points As Shown In The Above Figure And In The Below Figure Also. In Quassi-Associated Modes Of Signaling, The Messages Pertinent To A Particular Signaling Relation Are Not Transferred Over Transmission Links Directly Connecting The Relevant Signaling Points. Instead, The Messages Are Transferred Using Intermediate Signaling Points. In This Mode Of Signaling, The Path Taken By The Messages Through The Signaling Network Is Predetermined By Information Assigned By The Network.

Exchange A & B Have A Signaling Relation And Are Interconnected By Speech Paths. However The Signaling Path Used To Implement The Signaling Relation Is Via Exchange C And Not Directly Between A & B. In The Case Of Failure Of The A-B Signaling Link, The A-C-B Signaling Can Be Used To Control The Speech Path Between Exchanges A & B. Quassi-Associated Modes Of Operation Illustrate Great Flexibility And Powerful Nature Of Ccs System.






Speech
Path










Signaling Transfer

Fig. : Quassi-Associated Mode Of Operation

Requirements Of Ccs

The Ccs Has The Following Additional Requirements Introduced In Three Areas:
(I) Reliability And Security
(Ii) Speech Continuity
(Iii) Processing Overhead

1. A Signaling Channel Carried On A 64Kbps Link Has The Practical Capacity To Control Approximately 2000 Traffic Circuits. Hence The Failure Of An Inter Exchange Signaling Link Would Cause The Loss Of A Significant Amount Of Speech Traffic. For Access Signaling, The Loss Of The Signaling Link Would Means Isolation Of The Subscriber From The Local Exchange. It Is Therefore Essential To Take Exceptional Precautions To Avoid Such Losses.

2. Signaling Security Can Be Improved By Developing The Signaling Network Itself. In The Access Network, It Is Possible To Provide Two Signaling Links To A Subscriber (Preferably On Physically Diverse Transmission Links) & To Switch All Traffic To One Link When Other Links Interrupted. Similar Arrangements Can Be Made For Inter Exchange Signaling With Automatic Reconfiguration Of Signaling Paths, Even Via Different Exchanges To Maintain A Signaling Continuity In The Event Of Failure Of A Signaling Link.

3. The Unavailability Of Signaling Communication Between Two Exchanges Is Specified As A Maximum Of 10 Minutes Per Year.

4. Cas System That Use The Speech Path To Transfer Signaling Information Provide The Inherent Feature Of Checking The Continuity Of Speech Path Being Established Before Conversation Begins. If Continuity Is Not Achieved, The Signaling Transfer Is Not Successful The Call Is Aborted Or A Further Attempt Is Made To Connect Call. The Inherent Continuity Checks Is Absent In Ccs Systems, Owing To Separation Of Speech & Signaling Paths If Considered Desirable, Separate Speech Checks Can Be Provided.

5. The Flexible Manner In Which Ccs Systems Are Structured & The Implementation Of The Complex Network Feature Mean That Extra Processing Is Necessary To Operate Ccs. Even The Inherent Concept Of Funneling All Signaling On A Transmission Link Into Ccs Means That Messages Must Be Analyzed To Determine Which Circuit They Referred . However, This Extra Processing Overhead Is More Than Out Weighted By The Benefit Of Ccs Systems.

Salient Features Of Ccs

(I) Signaling Information For A Number Of Circuits Is Sent On A Single Channel. The Physical Tie Between The Signaling Path & Traffic Circuit Is Removed. All Signaling Transfer Relating To A Transmission Link Takes Place Over A Dedicated Signaling Channel. Hence, It Handles Information For Numerous Traffic Circuits.

(Ii) Signaling Is In The Form Of Data A Data Channel Operating At 64 Kbits/Sec. Rate Is Provided.

(Iii) Signaling Is Very Fast All The Required Digits Can Be Simultaneously Sent On The Data In The Form Of Message.

(Iv) It Can Also Work On 4.8Kbits/Sec. Link By Providing Modems.

(V) It Is Very Economical Between Exchanges Where Large Number Of Circuits Are Provided.

(Vi) It Can Cater For All New Services Such As Videotext, Data Communication, Facsimile And Isdn Services Etc.

(Vii) In Cas Systems, Signaling Capacity Is Dedicated To A Traffic Circuit. Limitations Exist On When Signals Can Be Sent, Depending On The Status Of The Call. For Example It Is Not Possible To Send Voice Frequency Signals During The Speech Phase Of A Telephone Call In Some Cas System, Unless Special Measures Are Taken (E.G. Provision Of Filter) Because Subscriber Are Able To Hear Tones. However Within These Constraints, It Is Not Possible To Send Signals Instantaneously. In Ccs Each Message Taken Up Whole Of The Signaling Channel For A Short Length Of Time. It Is Possible For An Exchange To Send Two Messages Relating To Two Circuits From A Transmission Link Exactly At A Same Time, Each May Take A Few Microseconds To Transmit. For This Reasons ‘Buffers Are Provided At Each End Of Ccs Link To Store Each Message Until The Link Becomes Available. As Messages Are Generated By An Exchange, They Are Stored In A Buffer And Transmitted In A Specified Order. When There Are No Messages To Transmit, There Is A Need To Maintain Synchronization Of The Signaling Channel Between The Two Exchanges. This Is Achieved By Continuously Transferring Synchronization Information Until A New Message Is Ready For Transmission.

(Viii) Ccs Systems Are Specified In Terms Of “Format” And “Procedures”. The Specification Of The Formats Defines The Structure Of Messages Used And Meaning Of Each Field Within The Message. The Specification Of The Procedures Defines The Logical Sequence In Which Messages Can Be Sent. The Procedures Of Ccs Circuit-Related Systems Are Closely Linked To Functions Within Exchanges That Control The Setup And Release Outgoing Calls. There Is Therefore A Close Relationship Between Ccs Procedures And Exchange Call Control And A Major Element In Defining Ccs Systems Is The Need To Achieve An Optimum Between These Factors.

(Ix) The Drive To Provide An Unrestricted Communication Capability Between Exchange Procedures Eliminates Per Circuit. Cas System But By Funneling All Signaling Information Into A Single Common Channel, Only One Signaling Termination Cost Is Incurred For Each Transmission Link. These Are Cost Penalties For Ccs Systems; The Messages Received By An Exchange Have To Be Analyzed Resulting In Processing Overheads. However These Are Covered By Increased Scope Of Inter Processor Activity.

(X) Cas System Posses Limited Information Transfer Capability To :
A) The Restricted Number Of Conditions That Can Be Applied (E.G. The Limited Variations That Can Be Applied To A Dc Loop Or Limited Number Of Frequency Combinations That Can Be Implemented In A Voice Frequency System)
B) The Limited Number Of Opportunity To Transfer Signals (E.G. It Is Not Possible To Transmit Voice Frequency Signals During The Conversation Phase Of Call Without Inconveniencing The Subscriber Or Taking Special Measures.
Neither Of These Restrictions Apply To Ccs The Flexible Message Based Approach Allows A Vast Range Of Information To Be Defined And The Information Can Be Sent During Any Stage Of A Call. Hence, The Reperoire Of Ccs Is Far Greater Than Channel Associated Versions And Messaged Can Be Transferred At Any Stage Of A Call Without Affecting The Calling And Called Subscriber.

(Xi) Ccs System Transfer Signals Very Quickly. A Message Used To Establish A Call In A Ccs System Can Contains All The Address Digits In An Information Field.

(Xii) Techniques Used In Modern Ccs Systems Can Be Further Improve The Flexibility Proved To Subscriber. ‘User-To-User’ Signaling Is A Technique Whereby Messages Can Be Transferred Form One Subscriber To Another Without Undergoing A Full Analysis A Full Analysis At Each Exchange In Network. Similarly ‘End-To-End’ Signaling Allows Exchanges To Transfer Information To Each Other Without Intermediate Exchanges Having To Fully Process The Messages.

(Xiii) One Of The Problems That Prompted The Development Of Ccs System Was ‘Speech Clipping’ In The International Network. In Some Cas Systems, It Is Necessary To Split The Speech Path During Call Set-Up To Avoid Tones Being Heard By The Calling Subscriber. This Results In A Slow Return Of The Answer Signal And, If The Called Subscriber Starts Speaking Immediately After Answer, Then The First Part Of The Statement Called By The Subscriber Is Lost. As The First Statement Is Usually The Identity Of The Called Subscriber, This Causes A Great Deal Of Confusion And Inconvenience. Ccs System Avoids This Problem By Transferring The Answer Signal Quickly.

(Xiv) As A Result Of The Processing Ability Of Ccs System, A High Degree Of Reliability Can Be Applied With A Resulting High Confidence In The Transfer Of Uncorrupted Information In The Case Of An Intermediate Exchange Failure, Re-Routing Can Takes Place Within The Signaling Network, Enabling Signaling Transferred To Be Continued.


Level Structure Of Ccs#7

Ccs#7 Is Optimized For Use In Digital Environment, But It Can Be Used In Any Transmission Medium. Ccs Is Highly Flexible, Facilitates The Evolutionary Process And Supports A Variety Of Services And Network Features. These Attribute Result From An Early Decision To Specify Ccs In A 4 Layer Structure A Illustrated In A Fig.

A Prime Objective When Formulating The Design Of Ccs Channel Was To Ensure That The Signaling System Flexibly Handle The Requirements For Circuit-Related Applications. These Applications Include Telephones And Circuit-Switched Data (I.E. Data Using Circuit Within Transmission Links In A Similar Way To Telephone Calls). The Functions Performed By The Four Layers Are Described.

Level 1- Physical Function.

Any Node With The Capability Of Handling Ccs Is Termed As ‘Signaling Point’. The Direct Interconnection Of Two Signaling Points With Ccs#7 Uses One Or More Signaling Links. Early Version Will Use Variation Of The Installed Copper Local Loops For Connection Between The Local Exchange And The Subscriber Premises; Later Version Will Undoubtedly Use Fiber Optics Technology. Level 1 Of The 4 Level Structures Defines The Physical And Electrical Functional Characteristics Of The Signaling Links. Defining Such Characteristics With In Level Means That Rest Of The Signaling System Can Be Independent Of The Transmission Medium Adopted. By Keeping The Interface Between Levels 1 & 2 Constant Any Changes Within Level 1 Do Not Affect The Higher Levels. In A Digital Environment The Usual Physical Link Is A 64Kbits/Sec. Channel. This Is Typically Within A Digital Transmission System Using Pulse Code Modulation. However Other Type Of Links (Including Analogue) Can Be Used Without Affecting The Level 2 To 4.



Level 2-Signaling Link Function.

Level 2 Defines The Function That Is Relevant To An Individual Signaling Link, Including Error Control And Link Monitoring. Thus Level 2 Is Responsible For The Reliable Transfer Of Signaling Information Between Two Directly Connected Signaling Point. If Error Occurs During Transmission Of The Signaling Information, It Is The Responsibility Of Level 2 To Invoke Procedures To Correct The Errors Such Characteristics Can Be Optimized Without Affecting The Rest Of Signaling Systems, Provided That The Interface To Level 1 & 3 Remains Constant This Function Is Achieved By

A) Initial Link Alignment, Synchronization And Proving To Ensure That The Link Error
Rate Performance Is Satisfactory.

B) Continuous Link Error Rate By Monitoring By Sending Fill In Signal Units During
The Idle Time.

C) Error Detection By Means Of The Fcs Field In Each Signal Units And Error Correction By Retransmission Of The Message Signal Unit.
The Above Measures Ensure That There Are Not More Than 1 In 1010 Signal Units With Undetected Errors And Not More Than 1 In 107 Lost Signal Units.

Level 3- Signaling Network Functions

These Functions That Are Common To More Than One Signaling Link I.E. Signaling Network Functions Are Defined In Level 3: This Includes “Message Handling” Function & “Signaling Network Management” Function. When A Message Is Transferred Between The Exchanges, There Are Usually Several Routes The Message Can Take, Including Via Signaling Transfer Points. The Message Handling Functions Are Responsible For The Routing Of Message Through The Signaling Network To The Correct Exchange. Signaling Network Management Function Control The Configuration Of The Signaling Of These Functions Includes Network Reconfiguration In Response To Status Changes Of Network, E.G. If An Exchange Within A Signaling Network Fails, The Level 3 Of Same Rout Message And Avoid The Exchange That Has Being Failed.

The Level 1 & 3 Constitute A Transfer Mechanism That Is Responsible For Signal Transformation In Messages From One Signaling Point To Another. The Combination Of Both Of Signaling Point Is Known As Message Transfer Part (Mtp). Mtp Does Not Understand The System Of The Message Being Transferred, But It Controls A Number Of Signaling Network And Network Messages. This Means That Messages Are Delivered To Routed Exchange In Uncorrupted Form And In The Sequence That They Were Sent, Under The Failure Conditions In The Network.

Level 4-User Messages Part

It Comprises The User Parts ,User Is Not Confused With The Subscriber. User Part Of Level 4 Of The Layered Structure And Include Messages, Message Coding And Messages Necessary To Handle Basic Telephony And Isdn Services. A Key Feature Is That The Management User Parts May Be Standardized Mtp. Three User Parts Have Been In This, These Are Telephone User Part (Tup), The Isdn User Part And The Data User Part (Dup). These All Are Defined In The Form Of Message Procedure And Formats.

Application Of Level Structure

The Application Of The Level Structure Is Illustrated In The Previous Figure. Exchange A & B Are Directly Connected By Speech Circuits. A Signaling Link Is Also Available Between Exchange A & B. It Is Shown That Level 4 Is Closely Associated With The Control Function Of The Exchange.

If The Control Function Of Exchange A Needs To Communicate With Control Function Of Exchange (E.G. To Initiate The Setup Of A Speech Circuit Between The Exchanges), The Control Function Of Exchange A Request The Level 4 Functions To Formulate An Appropriate Message. Level 4 Than Request The Message Transfer Part (Level 1 To 3) To Transport The Message To Exchange B. Level 3 Analyses The Request And Determines The Means Of Routing The Message To Exchange B .The Message Is Then Transported Via Level 1 & 2.

Upon Receipt Of The Message By The Mtp Of Exchange B, Levels 1 & 2 Deliver The Message To Level 3. Level 3 At Exchange B Recognizes That The Message Has Arrived At The Correct Exchange An Passes Message To Level 4. Level 4 In Exchange B Than Interacts With The Control Function To Determine Appropriate Action And Response. If Problem Arises In The Transmission Process Between Exchanges A & B, Causing Message Corruption, The Level 2 Function Are Responsible For Detecting The Corruption And Retransmitting The Information. If The Signaling Link Between Exchange A & B Is Not Available (E.G. Failure Of The Link), The Level3 Functions Are Responsible For Rerouting The Information Through The Signaling Network To Exchange B.

Using These Techniques, Exchange A & B Can Send Each Other Appropriate Message Until The Need To Communicate On A Particular Transaction Ceases (Speech Circuit Between Exchanges Is Released).























Call Processing In Ocb283



























Ocb 283 Functional Diagram



Steps:
(I) When A Subscriber Goes Off Hook, It Is Detected By Line Equipment. The Change In Loop State Is Detected By Microprocessor During Its Cyclic Scanning. The Csnl Allots Free Ts On Lr For This Call. The Csnl Prepares A New Call Message And Sends It To Pu/Pe (In Sma) Over A Signaling Link Through Mcx. The Message Is Sent In Local Version Of Ccs#7.

(Ii) Pu/ Pe Receives This Message And Sends It To Mr Over Mas. It Indicates Ur No. Ut No. (Line Card No.), Equipment No. And Time Slot Allotted.

(Iii) Mr Allots A Free Register To Handle This Call. It Notes Down Ur Number, Ut Number, Equipment Number And T/S Allotted For The Subscriber. Now Mr Obtains Ur-Lr To Smx-Lrx Correspondence From Mq.

(Iv) Mr Obtains Class Of Service Data From Tr.

(V) Mr Orders Com To Connect Dial Tone To The Free T/S Allotted To Subscriber. If Subscriber Has Dtmf Instrument Orders For Connection For Rgf To The T/S Of Subscriber And Then Orders For Dial Tone Connection.

(Vi) Mr Also Sends Acknowledgment Message To Csn.

(Vii) On Receipt Of Dial Tone, The Subscriber Dials Called Party’S Number. The Ut (Terminal Unit I.E. Subscriber Line Card) Disconnects Dial Tone From The Calling Subscriber.

(Viii) Csn Sends These Digits To Pu/Pe Through The Same Path And Signaling System.

(Ix) Pu/Pe Sends These Digits To Mr Over Mas.

(X) On Receipt Ion Pf First Digit, Mr Orders Com To Disconnect Dial Tone. (Ut Has Already Disconnected The Dial Tone From Subscriber).

(Xi) On Receipt Of First Two Digits, Mr Calls Tr For Pre Analysis. Tr, After Analysis Of First Two Digits Tells Mr, The Type Of The Call I.E. Local, Std Etc.


(Xii) After Receipt Of Adequate Number Of Digits (Or All The Digits In Case Of Local Call) Mr Again Calls Tr For Analysis. Tr Supplies Called Party’S Address And Charging Information N To Mr.

(Xiii) Mr Carries Out Party’S Test To Whether It Is Free Or Not (Path Mr-Pu/Pe-Csn).

(Xiv) Csn Test The Called Party’S Equipment. If It Is Free, It Connects The Ringing Current To Called Subscriber. It Also Allots A Free T/S On Lr And Sends A Message To Mr Indicating Lr-T/S Of Called Subscriber.

(Xv) Mr Order Com For Connection Of Ring Back Tone To Calling Subscriber. It Also Obtains Ur-Lr To Smx Lrx Correspondence For Called Subscriber. Mr Waits For Called Subscriber Reply.

(Xvi) When Called Subscriber Replies, The Concerned Csn Sends A Message To Pu/Pe. Pu/Pe Sends The Message To Mr.

(Xvii) Mr Orders Com To Disconnect Ring Back Tone Mr Orders Mq For Connection Of Calling And Called Subscriber Time Slot. Mr Also Orders Tx For Charging The Calling Subscriber. As Per Data Supplied By Tr, Mq And Tx Give Compliance.

(Xviii) The Subscribers Are Now In Conversation Phase. Mr Hands Over The Surveillance Of Calling And Called Subscriber. To Respective Csn And Release.

(Xix) When Calling Subscriber Goes Off Hook, Csn Informs Pu/ Pe. Pu/Pe Informs Mr. Mr Releases The Connection. If Called Subscriber Goes Off Hook, Mr Sets A One-Minute Timer And Releases The Connection After The Expiry To Of This Time.



Hardware Configuration

Ocb 283 Exchange Comprises Following Hardware Units:

1. Subscriber Access Units (Csnl, Csnd, Csed).
2. Trunk And Junction Connection Units (Smt).
3. Switching Matrix (Smx).
4. Auxiliary Equipments (Sma).
5. Control Units (Smc).
6. Communication Multiplex.
7. Time Base Generator (Sts)
8. Operation And Maintenance Unit (Smm).

The Subscriber Connection Units Csn, Smts And Smas Are Connected To Switching Network Through Pcm Links. The Interchange Of Message Between Smt, Smx, Smas And Control Units Smcs Takes Place On ‘Mas’ Token Rings. The Control Unit Interchanges Messages With One Another And With Smm On ‘Mis’ Token Rings. The Smm Is The Operation And Maintenance Functional Unit And Is Duplicated As Smma And Smmb. These Are Work In Pilot/ Standby Mode.

The Smcs Are The Units, Which Hold Control Functions Mr, Tx, Tr, Mq, Pc, Gx. These Functional Units Are In Software Form And Are Duplicated Except Mr, Which Can Be More Than Two. The Duplicated Function Work In Load Sharing Mode (Except Pc Which Works In Pilot/ Standby Mode Hence Smc Can Be Minimum 2 And Maximum 32 As Per Design.

The Sma Station Holds The Eta And Pupe Functions And These Are Also Minimum 2 To Maximum 32. Smt Station Which Is The Interface For The External Pcms Is Made Of Duplicated Hardware And Can Handle Either 32 Pcms If Smt1G Or 128 Pcms If 2G. The Smt’S Hardware Is Fully Duplicated And Functions In P/R Mode.

Lr





Lr





Pcm Junction Mas





Mis



General Architecture Of Ocb 283


Description Of Hardware Units

1) Subscriber Access Units :

Subscriber Connection Units (Csn) Are So Designed That They Can Be Equipped With Either Analogue Subscriber Or Digital Subscriber. Or Both. The Cards For Analogue Subscriber And Digital Subscriber Are Different, But Can Be Equipped In Any Slot Of The Shelf. Csn Can Be Either Placed In The Exchange Switch Room Or At A Remote Location. Further Subscriber Card Shelf Known As Concentrator Can Also Be Placed At The Rack Or At The Remote Location. These Features Provide Great Flexibility To Meet Any Type Of Requirement Of Dense Or Sparse Connection Densities. Depending Upon Their Location, Csn Is Known As Csnl Or Csnd And The Subscriber Shelf Is Known As Local Or Remote Concentrator Cnl Or Cne.
The Csn Enables The Connection
- Of Analogue Subscriber Lines:
• Standard 2-Wire Lines
• Battery Reversal
• Remote Metering
• Telephone Booths

- Of Digital Subscriber Line Giving These Subscriber To The Numeris Network Services.
• Basic Rate (2B+D: 2 * 64 Kbps + 16 Kbps)
• Primary Rate (30B+D: 30 * 64 Kbps + 64 Kbps)
• For Low Rate Data Transfer, The Csn Offers The Frame Service Which Allows The Transport Of Message In The D-Channel
Depending Upon The Distance Separating The Csn From The Exchange To Which It Is Connected, The Link Between The Exchange And The Csn Are Direct Or Use Pcm Transmission Mode. The Direct Connection Requires Less Equipment Then The Pcm Transmission Mode. The Csnl Is Connected To Switching Matrix Through A Minimum Of 1 Glr Or A Maximum Of 2 Glrs. Group Of 8 Lr Is Called As A Glr And Each Lr Is A Pcm Link Having 32 Time Slots. The Csnd Is Connected To Smt Rack Through A Minimum Of 2 Pcm And A Maximum Of 16 Pcms.
The Message Interchange Between Csn And Control Units Takes Place On Common Channel Signaling Using Local Version Of Ccs37 Signaling. The Csn Is So Designed That It Can Be Connected To Any Switch Supporting Ccs#7 Signaling. This Csn Can Have One Basic Rack And Up To 3 Extension Racks. Its Architecture Can Be Broadly Divided Into Two Parts, These Are

(I) Digital Control Unit (Ucn).

(Ii) Concentrators (Cnl Or Cne).





(I) Digital Control Unit (Ucn)

The Digital Control Unit Is The Interface Between Concentrators And The Exchange. It Is In Basic Rack. The Basic Rack Is Placed In Switch Room For Csnl And At Remote Location For Csnd. It Can Be Further Broken Down Into Two Parts,

A) Control And Connection Units (Ucx)

There Are Two Such Units, Which Are The Controlling Logics Of The Csn. These Operate In The Pilot/ Standby Mode. The Active Ucx Controls The Working Of Csn And Also Updates Standby Ucx. In Case Of Any Faults In The Active Ucx, The Switch Over Takes Place Without Interruption To Existing Traffic. This Comprises A Processor Board Tpucd, A Coupler Board Tccsc And A Switching Matrix Tcrcx.

The Tpucd Board Performs The Control Unit And Memory Function For The Csn Logic. It Is ‘Master Station’ Comprising An I486Sx Microprocessor Clocked At 20 Mhz, An 8-Mb Ram Organized In 32-Bit Word. It Has Also Interchange Memory Function. This Is A ‘Slave Station That Comprise Mainly A 4-Mb Private Memory Organized In 16-Bit Word.

The Tccsc Board Supports Svc7 Coupler, It Provides Level 2 Of Signaling Protocol No.7 For 64 Kbits Channels. This Coupler Also Provides Level 2 Of The Uc-Ut Dialog Protocol. This Board Also Has Rxcn Coupler; It Is Used For Network Marker And Pcm Alarm Management. This Board Also Has Auxiliary Function, Used For The Generation Of The Idle Code On The Available Channels.

The Board Tcrcx Makes Up The Csnd Switching Matrix It Has An Internal Parallel To Serial Interfaced Designed To Control The Time Division Switching Matrix Gate Array. This Network Consists Of A Single Time Division Stage. It [Provides For The Sequencing Of The N * 64 Kbits Links. This Switching Matrix Has Different Interface On The Lri Side And Bipolar Interface On The Lre Side. It Also Has A Passive Control Of Connections. It Is Used For Generation Of Timing And Synchronization Signal. Required For The Operation.

The Board Tcsuc In Charge Of Coupling The Csn Control Logics. This Board Is Functionally Divided Into 3 Sub Units. First Sub Unit Processing The Switch Over Generated By A Fault, Second Sub Unit Processing The Gradual Switchover Requested By The Pilot Logic, The Third Subunit Processing The Resets Either Induced By Logic Faults Or Controlled Manually Or By A Super Watch Dog Device.

Auxiliary Equipment Processing Group (Gta)

This Auxiliary Processing Group Includes A Number Of Csn Auxiliary Functions Namely

• Generation Of Tones And Recorded Announcements For The Local Communication In Case Of Remote Connection To The Exchange. It Is The Role Of The Tfilm

• Recognizing The Two Frequency Signals Of The Pushbutton Subscribers Telephone Through Appropriate Receivers. In Case Of Ocmt, Supplementary Frequency Receivers Can Be Loaded With Digital Concentrators Because The Two Trf8 Planned For The Gta Can Be Insufficient To Process The Whole Pushbutton Analogue Traffic

• Csn Alarm Processing In The E Case Of Csn Connected In Remote Mode. This Operation Is Performed By Means Of The Tcpos.

• The Test Of Subscriber Line Connected To The Local Numeric Concentrators Through Tmln Associated To Its Commend.


Concentrators

The Shelf, Which Accommodates Subscriber Line Cards, Is Known As Concentrators. The Concentrator Can Either Be Co-Located With The Digital Control Unit In Which Case They Are Known As Local Concentrators Cnl Or At Remote Location In Which Case They Are Known As Remote Concentrators Cne. When A Remote Concentrator Is Used Then To Connect Exchange Pcm To Digital Control Unit An Interface Shelf Icne Is Required. The Maximum Capacity Of A Concentrator Is 256 Subscribers. When All The Concentrators Are Local A Maximum Of 19 Concentrators Can Be Equipped In One Csn Having 4 Racks, Where As If All Are Remote Or If At Least 2 Are Remote, A Maximum 20 Csn Can Be Equipped In One Csn. Depending Upon The Configuration Each Cnl Accommodate Following Type Tus.

• Individual Subscriber- Tabas, Tabazb, Tabasb
• Special Subscriber- Tabaf, Tabazf
• Dedicated Links Lf2-4 Wires: Tdqf
• Multi Way Junction Of 64 Kbps Tadl
• V5.1 Interface Tcv51
• Digital Subscriber With Basic Rate Access Tabn2G, Tabn3G
• 1 Reception Terminal Unit For The Digits Transmitted By The Push Button Subscriber Sets Trf8
• 2 Clock And Network Line Interface Tchlr, Tchle
• Digital Subscriber With Primary Rate Access Tadp, Tadpb, Tadpb2

Tabas, Tabazb: These Tus Comprised Of Subscriber Line Interface That Divide The Transmission And Reception Speech Channels And Power Up The Subscriber Line Through An Resistance Bridge Of 2* 200 Ohms For Tabas And 2 * 400 Ohms For Tabazb

Tabaf, Tabazf: These Uts Enables The Connection Of 16 Analog Subscriber Lines With The Remote Charging And Battery Reversal Functions. The Equalization Impedance, The Transmission And Reception Gains As Well As The Line Current Limitation Can Be Programmed For Each Subscriber Line Interface Circuit And Takes Four Values.

Tdqf: This Ut Is Supposed To Connect Up To 4 Dedicated Link Of Low Frequency To 2 To 4 Wire Wires Used To Apply Specific Application Such As High Quality Transmissions.

Tadl: This Ut Enables To Connect M/W Junction At 64 Kbps Used For Specific Application.

Tcv51: This Ut Enables The Connection Of An Access Network On To The Csn Through A V5.1 Interface. It Is Considered By Exchange As Ut With 32 Possible Equipments Units. It Only Enables The Support Of 30 Analogue Subscriber Or 15 Isdn Subscribers. The Allocation It Number To V5.1 Equipment Is Done Upon The Creation `Of A V5.1 Subscriber, An Analogue Subscriber Using An It And An Isdn Subscriber Using 2 It’S Of The V5.1 Pcm.

Tcpol: This Ut Takes Part In The Cnl Defense And Performs Under The Ucn Control. It Is Used For Blocking One Or More Uts By Blocking Wire, Which Entirely Isolates The Involved Ut On Transmission. This Prevents Any Disturbance On The Links By A Faulty Ut. Signaling Of The Timing Signal Distribution Faults Seen By The Interface Board Tchlx. It Also Isolates The Bus In Charge Of Switching To The Subscriber Line Test Circuits And Its Connection To The Cnl Internal Test Device Or External Test Device. Testing Of The Signaling Transmitted By The Subscribers Line Equipment.

Trf8: This Terminal Unit Analyzes The Frequencies Transmitted During Dialing From A Subscriber Push Button Set And Transforms Them Into A Message That Indicates The Number Dialed. It Comprises 8 Frequency Receivers, Allowing The Recognition Of The Numbers Corresponding To 8 Simultaneous Calls..








Connection Of Local And Remote Concentrators To Csnl

2) Trunk And Junction Connection Unit (Smt) :

Pcm Time Slot By Smt. The Sab Function (Branch Selection And Amplification) Is This Is Also Known As Pcm Trunk Control Station. This Smt Provides An Operational Interface Between The Pcms Coming From The Exchange (Csnd Or Csne) And The Switching Center. The Current Version Of Smt Being Supplied To Our Exchanges In India Is Smt2G. It Is New Functional Variant Of The Smt Station.

Smt2G Consists Of Duplicated Processing Subsystems. Smta And Smtb, Which Are Connected Through Internal, Links Lism. Both Of Them Are Connected To Pcm Interfaces As Well As To Mas Token Rings. Pcms Are Connected To Pcm Interfaces, Which Are Not Duplicated. Smt2G Is Connected To Smxa And Smxb Through 128 Pcms, Which Are Connected To Sab Branch A, And Sab Branch B. Speech Samples Are Sent On Both The Branches From Smx, But One Which Is Better Is Selected And Connected To The Concerned Also Not Duplicated. Out Of The Two Processing Logics, Smt A And Smt B, One Remains Active And Other Standby. In Case Of Fault In Active Logic, Automatic Switchover Takes Place Providing An Uninterrupted Service. Also Locovar Is Activated On The Faulty Logic And The Diagnostic Is Displayed On The Terminal For The Information Of The Maintenance Staff.

The Software Mlurm Is Loaded In The Smt To Perform Functions Of A Pcm Controller.

The Functions Performed On Receive Side-
• Convert Hdb3 Code To Binary.
• Extract Channel Associated Signaling.
• Manages Ccs#7 Messages Carried On Ts 16.
• Cross-Connects A Channel On Pcm To Ts On Lr.

The Functions Performed On Transmit Side-
• Convert Binary Code To Hdb3 Line Code.
• Inject Channel Associated Signaling
• Manages Ccs#7 Messages On Ts 16.
• Cross-Connects A Ts On Lr To A Channel On Pcm.
The Organization Of Each Smt Is Based On The Bsm And Includes
O A Main Multiplex Line Driver (Cmp).
O An Optional Pup Function.
O A Common Memory Function.
O One Or Two Sm Exchange Termination Interface Controller



Lae/Las 128
Lrs


Lism

128
Lrs
Mas Mas
A B
Lae/Las
64 Pcm General Architecture Of Smt 2G
The Functions Are Implemented On The Following Boards

O Cmp: Acaja And Acajb Boards
O Pup: Acutg Board
O Mc: Acmgs Board
O Ctlh: Ictsm Board

The Control System Comprises Two Processing Subsystem Or Individual Sm Station Having A Direct Inter Sm Interface Enabling Them To Communicate. This Architecture Is Dictated By The Operating Mode To Guarantee Dependability, A Duplicated Sm System Is Needed. The Concept Of Active Sm Is Retained In The Etp Initialization Process, Where Only The Active Sme Is Recognized. A Hardwired Device Divided Between The Two Smes And Physically Implemented On The First Ictsm Board Of Smes Handles Control And Positioning Of The Prs Signal.
Knowledge Of The Active Smes Is Sent To The Outside Environment Via A Hardwired Signal Prs. The Signal Is Needed Among Other Things By The Etp To Know Which Processing Subsystem Is Active During The Initialization Phase.

The Cmp Comprise Two Boards For Connecting The Station To A Multiplex (Duplicated Ring), A Master Board Acaja Based On 68020 Microprocessor. This Board Supports Ring A Of The Multiplex And Provides The Processing Power. It Is Connected To The Bsm. A Slave Board Acajb Controlled By The Acaja Board Processor Supports Ring B Of The Multiplex And Is Not Connected To The Bsm.

Acmgs, This Is A New Generation Common Memory With A Capacity Of 16 Mbytes Protected By A Self-Correcting Code For Each 32-Bit Word. The Slave Board Never Attempt-Pts To Seize The Bus But Is Accessible To All Master Boards Through Its Memory Plane And Its Interface Area. When Used With An Acutg Cpu Board, It Offers This Board A Direct Interface Via A Local Bus. The Function Of This Board In The Unit Is To Enable The Various Master Processors To Communicate In Message Mode Via Queues And Also Provide A Protected Information Storage Area For Permanent And Semi Permanent Programs And Data.

The Ictsm Board Is Organized Around A Common Acutg Section (68030, Partly Protected 4 Mbytes Dram Standard Private Peripheral Devices And Bsm Interface). The Sme Switchover Management Devices Supplement This Basic Function. Inter Smes Dialogue. The Ictsm Board Number (I) Is Linked To Its Counterpart In The Other Smes Via A Programmable Bit Rate Hdlc Link, Lism That Is Designed To Facilitate Interchanges Between Equivalent Boards.

3) Switching Matrix (Smx) :

The Smx Station Is An Element Of The Central Connection Matrix Of The Ocb283 System. Under The Control Of The Control Stations, It Performs The Following Functions.
• Clock Reception And Distribution
• Control Of The Station
• Interface With The Connection Units And The Other Smx Stations
• Connection Of Cx Input Lines To 256 Cx Output Lines.
• Connection Security.
• Help In Fault Location Of The Locovar
• Station Alarm Processing.

The Switching Network In Ocb283 Is Single ‘T’ Stage System. It Is Made Up Of
A) Host Switching Matrix
B) Branch Selection And Amplification

A) Host Switching Matrix

The Host-Switching Matrix Consists Of Two Identical Branches A And B. The Host-Switching Matrix Is Implemented On The Hardware Units Known Matrix Control Station (Smx). Each Host Switching Can Host Up To 2048 Incoming Pcm Links (Lre) And 256 Outgoing Pcm Links (Lrs). Out Of 2048 Incoming Links, Only 256 Links Are Directly Coming Fro This Matrix Control Station. The Remaining Links Are Coming Fro Other Seven Smxs. In Full Configuration, The Host-Switching Matrix Is 2048 * 2048 Matrix. This Is Shown In Below Figure.

A Matrix Control Station Can Establish Connection Between Ant Ts On2048 Lre And Any Ts On 256 Lrs. Similarly A Host-Switching Matrix Can Establish Connection Between Any Ts On 2048 Lre And Any Ts On 2048 Lrs. Three Standard Configurations With 256 Lrs, 1024 Lrs And 2048 Lrs Are Available. The Matrix Control Station Is Built Around A Processor, Which Implements Software Machine Malcom Functions, To Establish And Break Connection Between Time Slots. It Also Carries Out Two-Way Communication With Other Units In The System Over Mas Rings.

0 To 256 Lre
0 To 255 Lrs



256 To 511 Lre 256 To 512 Lrs




1792 To 2047 Lrs







The Time Switch Comprises Of A Speech Buffer Memory, A Control Memory, An Incoming Highway Of Digital Speech In Parallel Bits And An Outgoing Highway As Shown In The Diagram. This Is A Input Associated Time Control Switch. In This Switch The Buffer Memory And The Control Memory Are Controlled Write Type I.E. The Writing In Its Control. The Control Function Writes In The Control Memory At The Location Corresponding To The Incoming Time Slot Number The Location Where Ir Should Be Written In The Buffer Memory. Both These Memories Are Sequential Read Type. Reading Of Control Memory Gives The Address In Buffer Memory For Writing The Incoming Byte. Thus Reading Of Buffer Memory Sequentially The Ts Will Be Read Fro The Location Given By The Control Memory. Thus A One-Way Time Switching Has Taken Place. Similarly A Both Way Switching Requires Two Sets Of Such Switches.

The Switching Is Done In Ocb283 In Two Fully Duplicated Branches Simultaneously. For This Purpose For Each Connection Units The Lr Links Originates In To Parallel Branches Toward Two Parallel Sets Of Switching Matrices Called Smxa And Smxb. The Branch Of Such Networks Are Called A And B Branches. Also The Received Side Lr Links Come From Both The Smxs A & B And Are Terminated On The Respected Connection Units. Referred To As Ur In Figure Below. The Duplicated Branches Of Switching Have Been Designed To Provide High Reliability Switching Path For Such Diverse Purpose As Data Switching, Video Conference, And Isdn Applications Etc. With The Duplicated Path Of Switching If There Is Error In One Path The Other Path That Is Good Can Be Used Continuously Without Interrupting The Call In Progress.

B) Sab Function :

The Connection Unit Has Their Internal Duplicated Hardware, Which Is Called Control Logic, Which Works In Pilot/ Reserve Arrangements. Also They Have Non-Duplicated Hardware Such As Subscriber’S Cards And Pcm Termination Cards. The Duplicated Lrs Originate From Function In Connection Units Called Sab (Selection And Amplification Of Branch). Its Role Is To Generate Two Sets Of Lrs In Trans Direction With Calculation Of Parity Etc. And Compares To Detect Any Error In The Two Branches. In Case Of Error The Sample From Only The Good Branch Are Taken After Automatic Testing Of The Transmission Of Both The Branches By The Common Control And The Faulty Branch Is Withdrawn From The Service. The Connection Unit Lr Links Are Formed Into Group Of 80Lrs At The Factory Into Cables With Both Ends Terminated With Plugs For The Convenience Of Installation. Such Group Of Lrs Is Called Glr. The Figure Shows How The Glrs Are Terminated At The Two Branches Of Smx In Ocb 283.


4) Auxiliary Equipment Control Station (Sma)

The Sma Station Receives The Auxiliaries From The Ocb283 Exchange. These Are
• Frequency Receive/ Generator Used For Setting Up Calls
• Conference Circuits.
• Tone Generator, Time Management Operator
• Ccitt Number 7 Signaling Receiver/ Transmitters.

This Sma Is Linked To The Switching Matrix By A Set Of 8 Lrs (O/G Matrix Links) Carrying The Signals Generated Or To Be Analyzed, Through The Switching Matrix The Sma Receives The Basic Timing Fro The Exchange. To The Mas Series Communication Support Facility, It Ensures Information Transfer Between The Sma And The Ocb283 Command Units. To The Alarm Multiplex. The Sma Contains The Following Two Functional Units
(I) Eta
(Ii) Pupe

Eta Contains The Following Subscriber Components:
• Frequency Receiver/ Generators
• Conference Call Circuits
• Tone Generators

The Frequency R4Eceivers/ Generator Recognize The Digits Dialed Through Dtmf Instrument And Also The Mf (R2) Signals Received On Junctions. They Also Generate The Various Frequencies Required For Mf Signaling And Testing Etc.
The Conference Circuits Are Used To Setup Connection Between A Maximum Of 4 Subscribers. These 4 Subscribers Can Hold Conference On The Telephone I.E. They Can Talk To Each Other.
Tone Generator Generates The Various Tones Required To Be Connected During Call Processing. These Tones Are Dial Tone, Busy Tone, Ring Back Tone, Processing Tone Etc.
Pupe Performs The Level 2 And Part Of Level 3 Functions For Ccitt No. 7 Signaling. The Rest Of The Level 3 Functions Performed By Pc. The Various Functions Performed By Pupe Are As Below

Transmit Side
• It Sends ‘Flag’ And ‘Check Bit’ In The Hdlc Frame While Transmitting Ccs#7 Messages. It Also Inserts Zeros, When There Are More Then 5 Consecutive Ones In The Message.
• Pupe Send Filling Signal Units (Fisu) Automatically When There Are No Messages To Be Sent.
• Pupe Also Sends Link Status Signal Unit (Lisu) When Commanded.
• It Retransmits A Signal Unit On Receipt Of Negative Acknowledgement.

Receive Side
• On The Receipt Of Ccs#7 Signaling Messages, It Eliminates Zeroes Which Were Inserted After Five Consecutive Ones.
• It Detects The Flag And Also Computes The Checksum And Compares Them With Check Bits. If These Two Matches, It Sends Positive Acknowledgement Otherwise It Sends A Negative Acknowledgment.
• It Eliminates Fill In Signal Units, As They Do Not Carry Any Information.

Either Eta Or Pupe Or Both Can Be Implemented On The Same Sma. When Both Are Implemented On The Same Sma, Mlpupe (Logic Machine Pupe I.E. Pupe Software) Is Loaded On The Principal Processor (Pup) And Mleta Is Loaded On Secondary Processor (Pus)
When Only Pupe Is Implemented On Sma, It Is Loaded On Pup And When Only Eta Is Implemented, It Is Loaded On Pus. Only First Two Etas Have Tone Generators Ccfs And Rgfs Are Provided As Per Requirements. The Pcb Used Is Common For Rgf; Ccf And Tone Generators. Only The Software Is Different. When No Ccf Or Tone Generator Is Required An Eta Can Have Maximum Of 96 Rgfs. An Sma Is Connected To Smx By 8 Lr Links. The Following Table Illustrates The Capacity And Modularity Of Sma.

Sma Units Equipped With Capacity Max & Min.
Eta Alone 96 Rgf 2 To 32
Pupe Alone 64 Ccs#7 Channels 2 To 15
Eta And Pupe Both 64 Rgfs/ 32Cccs#7 Channels 2 To 15
The Sma Is Organized Around A 16 Bit Standardized Bsm Bus. Sixteen Boards Can Be Connected To The Bsm:

1. An Acaja Board Intended With The Assistance Of The Acajb Board To Mange Transfer Via The Mas Call Multiplex.

2. An Acmcq Board Supporting The Mass Memory Of The Station.

3. An Acutr Board, Which Provides Backup Processing Power.

4. A Maximum Of 12 Board S Carrying Out Specific Operations Devolved To The Sma.

5. A Pair Of Icid Board Which Provides Link Between The Branches Of The Connection Matrix And The Sma.

6. And Acala Board For The Collection And Transmission Of Alarm Read In The Sma.

Ictsh Functions The Simultaneous Call Function. Simultaneous Call Involving Up To A Maximum Of 4 Subscribers Is Possible. This Function Enables Add-On Conferencing With The Possibility Of Discreet Listen, Indicating A Call In Hold, Making Operator Calls. The Tone Generator Function Generates Voice Frequency Signal These Signals Are Single, Two, Three Or Four Frequency Sequence Includes A Maximum Of Eight Send Pause Sequences. An Ictsh Board Generates 32-Voice Frequency Signal. Frequency Composition And Sequencing Are Transmitted On Sma Initialization And Remains Through Out Operating Phases. The Rgf Terminal Analyzes And Sends Voice Frequency Signals; These Signals Are In General Single Or Two Frequencies And Attached To A Signaling Code. An Rgf Terminal Is Dynamically Placed By Control Units Within A Signaling Code It Detects The Presence Of Receive/ Incoming Signals And Transmit Their Frequency Composition To The Control Stations. It Always Transmits As A Response To Mono Or Bi-Frequency Pulse Control Instruction. Eight Rgf Terminals Can Be Implemented On Ictsh.

Achil Functions On 16 Channels It Carries Out Level 2 Hdlc Type Signaling Processing And Has Two Servers, Which At The Frame Level Has The Following Role
Hdlc Direction, On Send (Sending Of Flag Crc Calculation ‘0’ Insertion) And On Receive (Elimination Of Inserted ‘0’S Flag Termination Crc Verification). Ccitt#7 Directions On Send (Automatic Send Of Filler Frames, Repetition On Command Of Status Frames) And On Receive (Automatic Elimination Of Filler Frames Not Carrying Useful Information).

Ichor Board Maintains Time For The Ocb 283 Exchange. Time Information Is Doubly Useful In Switching. It Enables Determination And Labeling. It Must Be Protected Against Slow Drift, Which Implies The Need For Repeated Time Resetting And Protection Against Sudden Loss Caused By Hardware Faults Normally.

Acaja And Acajb Board Is A Coupler Connecting The Sma To Mas Multiplex And Enabling The Dialog With The Control Units. The Information Exchanged Is Channel Associated Signaling From The Ictsh Board. These Are Signals Sent By The Rf Of The Rgf Station Signals Detected In Voice Frequencies. Messages From And To Applications Implemented By Sma Processor.

Acala Board Collects Alarm And Is Self Powered. In Sma The Alarm Sending Entities Are The Two Converters Of 48 Volts.

Icid Board (Differential Interface Board) Provides For The Security Of The Matrix- Ur Link In The Ocb 283. It Supports The Following Functions

• Reception Of 8 Lrs And Of Associated Time Base From Rcid Board Of One Branch Of The Mcx.

• Sending Of 8 Las And 4 Associated Time Base To The Urs (Sma, Smt)

• Mutual Help By Reception Of 8 Lrs Fro The Other Branch Of The Mcx With The Associated Dts.

• Selection Of Time Base.

• Processing Of Extra Bits Transmitting On The Lrs.

• Generation Of Availability Signals Accompanying Lass.

• Processing Of Lae Links Sent By Urs And Generation Of Lre. (I/C Matrix Link).

• Synchronization Of Lrs From The Mcx And The Mutual Help Of Lrs.

5) Control Units (Smc):

Since All The Control Units Like Mr, Mq, Tx, Tr Etc. And Sma Are Implemented On A Common Type Of Hardware Architecture Known As Station. It Is Worthwhile To Understand The Architecture And Concept Of Station. A Station Is Built Around A Multiprocessor Station Bus Bsm. One Or More Processor And One Or More Intelligent Couplers Connected To This Bus. They Interchange Data Through The Common Memory. The Principal Or Main Processor Is Connected To Common Memory Through A 32 Bit Private Bus Apart From Through Bsm. All The Processor Are Motorola 68020 Microprocessor And Operates At 15.6 Mhz Clock. Multiprocessor Station Bus Bsm Is 16-Bit Bus, Which Operates At 44.8 Mbs.
A Block Schematic Of The Station Is Shown In The Figure Below.

















Smc Station Configuration

There Can Be One Principal Processor (Pup) And 4 Secondary Processors (Pus) In A Station. Similarly There Can Be One Main Coupler (Cmp) And Up To 4 Secondary Coupler (Cms). Specific Coupler Can Be Equipped For Specific Purposes. A Station Can Function As Mr, Tr Or Any Other Unit When Particular Software Is Loaded In The Station. Depending On Traffic And Processing Requirements, Software Of Either One Or Functional Units Can Be Loaded In The Same Station. Also Depending On The Above Requirements, A Functional Unit Can Be Implemented On Principal Or Secondary Processor And On Main Or Secondary Coupler.

To Permit Co-Habitation Of Many Software Machines Ion The Same Station, Basic Software Is Known As Hyper Visor Is Provide On The Station. Another Software Known As Supervisor Provides Communication And Loading Facilities. The Station Is Generally Known As Smc.

There Are 6 Common Control Function In A Ocb283.The Following List Illustrates Their Minimum And Maximum Numbers.


S. No. Name Of Unit Minimum Maximum
1 Mr 2 7
2 Tr 2 2
3 Tx 2 2
4 Mq 2 2
5 Pc 2 2
6 Gx 2 2


They Are Known As Logical Machines In Software Form. These Logical Machines ‘Ml’ Are Implemented On The Hardware Of Smc By Loading Suitable Software On It. An Smc Can Support Any One Or Many Mls Or Functions In Defined Combination. Accordingly Depending Upon Exchange Configuration And Traffic Requirement There Can Be Minimum Two Smcs Required And Maximum Number Of Smcs Can Be Minimum 32 But No More Than 15 Are Needed. The Planners And Manufactured Upio N The Traffic Data Decide The Required Number Of Smcs. In Addition To This Provision Of One Backup Smc Station. This Backup Station Is Not Loaded With Any Software.

Whenever, Any Smc Becomes Faulty It Sends Message To Smm. The Smm Blocks This Unit And Inform All Control Units Regarding Non-Availability Of This Unit. Smm Then Loads The Software Of All The Functional Units On The Backup Station And Brings It Into Service. Thus, There Is Automatic Recovery. Smm Also Runs Diagnostic Program On The Faulty Station And Prints Diagnostics On The Terminal.

Functions Of Various Common Control Software Mls. :


(A) Multiregister (Mlmr)
The Mr Establishes And Releases The Calls It Takes Real Time Decision Or Processing Of A Call. The Mr Also Consults Tr To Find Out Subscribers Entitlements And Stores Digits Dialed By Subscriber. It Also Orders For Connection And Is Connection Of Various Tones And Subscribers. In Addition To Call Processing Functions, Mr Also Carries Out Testing Of Circuits And Observation Function.

(B) Translator (Mltr)
The Tr Stores Exchange Database In Its Memory. On Request It Tells Mr The Characteristics And Entitlement Of Subscriber And Circuits. The Tr Also Stores The Routing And Analysis Data. It Converts Or Translates The Received Digit Into Equipment Number Of The Called Subscriber.

(C) Marker (Mlmq)
The Marker Carries Out Message Between Common Control Functions Mls And Connection Units For Subscribers Or Circuits. It Also Acts As ‘Gate’ For Message Which Pas From One Communication Domain Top Another. The Mq Also Supervises Semi Permanent Connection In The Network.

(D) Charging Unit (Mltx)
As The Name Suggests The Tx Carries Out Charging For Each Communication Set Up. It Also Keeps Charge Account Of All Subscribers. The Tx Also Prepares And Sends Detail-Billing Message To Smm. In Addition It Also Carries Out Subscriber And Circuit Observation Functions.

(E) Matrix System Handler (Mlgx)
The Gx Monitors The Connection In The Switching Network And In Case Of Fault, Carries Out Appropriate Defense Functions. It Also Periodically Or On Request Monitors Internal Links In The Switching Network.

(F) Ccs#7 Controller (Mlpc)
The Pc Carries Out Routing And Traffic Management Functions, Part Of Level 3 Functions For Ccitt No. 7 Signaling. It Also Carries Out The Defense Of Pupe, I.E. If A Pupe Develops Faults, It Is Automatically Blocked, The Semi Permanent Link Is Reconfigured And The Standby Pupe Is Brought In Service. The Pc Also Carries Out Observation Functions.


6) Communication Multiplexes (Mis, Mas And Mal) Token Rings:

In Ocb 283 Exchange The Communication Multiplex Highway Are Utilized For Interchange Of Messages Between Various Equipments Of Exchange. These Communication Multiplex Works On The Principal Of Computer Circular Lan Ring Using Token Ring Protocol. There Are Three Types Of Communication Multiplexed Highway According To Their Use.

1. Mis Interstation Multiplex

2. Mas Station Access Multiplex

3. Mal Alarm Multiplex.

The Mis Token Ring Is Providing For Interchange Of Message Between Two Smcs And Between An Smc And Smm.

The Mas Are Provided For Interchange Of Message Between Csnl, Smt, Sma And Smx On One-Hand And Control Units (Smc) On The Other Hand. A Maximum Of Four Mas Token Rings Is Provided In Compact Configuration

Mas Token Ring Can Be Minimum Nil And Maximum Four Duplicated As A & B.Mal Token Ring Is Provided To Handle Exchange Alarms From All The Hardware Stations Of Exchange Except Csnl.The Token Ring Confirm To Ieee 802.5 Standard And Operates At 4 Mbps. An Empty Token Circulates On The Ring When There Is No Message To Be Sent. A Token Contains Starting Flag, Access Control Byte And End Flag Of One Byte Each As Shown Below In Table.

Whenever A Station Wants To Send A Message It Checks The Status Of T Bit. If Tbit Is Zero The Token Is Free, So The Station Inserts Its Message In The Token And Sets T=1, The Station Books The Token To The Next Message. However If The Token Is Busy Which Is Indicated By T=1 The Books The Token By Writing Its Priority In Reservation Field. Whenever A Station Receives The Token, It Compares Its Own Address With The Destination Address Written In The Token. If The Address Matches The Station Receives This Message And Sends Acknowledgement. On Receipt Of Acknowledgement, The Transmitting Station Clears The Token And Sets The T Bit To Zero. If A Station Has Booked A Token, It Can Send The Message Only After It Has Been Released By The Transmitting Station

7) Time Base Generator (Sts):

Time Base Is Required To Synchronize Pcm Links Connected To Connection Units Like Csnl, Smt, And Sma Etc. The Time Base Is Generated Time Base Synchronization And Time Base Station (Sts) And Distributed To The Two Branches Of The Switching Network. These Branches Then Redistributed The Time Base To Above Mentioned Connection Units Along With Lrs. Sts Has Three Oscillators All Generating 8 Mhz And Sbt Time Base. The Switching Network Selects The Time Base As Per Majority Logic. So Even If One Of The Oscillators Is Out Of The Order, The System Is Not Affected. Sts Receives Sbt And 8Mhz But Supplies Sbt And 4 Mhz To Connection Units. There Is A Facility To Synchronize These Oscillators With An External Source By Equipping External Synchronization Network. This Facility Is Useful When The Exchange Has To Be Synchronized With The Network.

Empty Token:



8 Bit 8 Bit 8 Bit
End Flag Access Control Ac Start Flag

P P P T M R R R


Token With Message:


Sd Ac Fc Da Sa Info Fcs Ed Fs Fl












Token
Ring








(8) Operation & Maintenance Unit (Smm):

Smm Station In Ocb 283 Performs The Operation And Maintenance Functions. The Smm Station Has Full Duplicated Hardware Smma And Smmb. One Of The Two Smm Is Pilot And The Other Work As Hot Stand-By. For Both Smm There Are Two Mirror Images Hard Disks Of 1200 Mb Capacity. Pilot Smm Is Able To Access Either Of Disks. There Are Termination Of Peripherals Tty, Vdu For Operation And Maintenance. Smm Dialogues With All Smcs Over Mis Token Ring. Adjacent To Smm Rack There Is One Magtape Drive Unit Dbm. There Is One Streamer For Cartridge Drive In Smm Rack. There Are Up To 4 Alarm Reception Rings For Handling Exchange Alarms. Smm Receives All Alarms From Whole Exchange On Alarm Rings Mal. Smm Station Occupies Three Shelves Of A Ca Rack. Smm Rack Also Has Digital Voice Announcement System Mpna In Fourth Shelf.

The Smm Station Supports The Local Operational Maintenance Unit Om Handling Ocb 283 Supervision And Management Function. This Smm Is Provided To Supervise The Functioning Of Various Exchange Equipment And To Take Suitable Action In Case Of Malfunctioning Of Any Equipment. As Stated Earlier It Does The Defense Of Control Units In Case Of Faults. All The Files And Data Are Stored In Smm Hard Disk, Which Can Be Loaded In Any Unit. Smm Also Carries Out The Re-Initialization Of The Exchange When Required. The Smm Process Man Machines Commands And Execute Them. Smm Also Collects The Alarms From Various Units And Process Them. Smm Stores Detailed Billing Data In The Disk, Which Can Be Periodically Transferred To Magtape For Processing. Smm Runs Diagnostic Programs (Locovar) On The Faulty Units And Indicates The Faulty Pcb. In Nutshell, The Smm Executes All The Functions Related To Operation And Maintenance Of Ocb 283 Exchange.

The Smm (Maintenance Multiprocessor Station) Is Built Around Two Identical Microprocessors 68030. This Multiprocessor Station Work In Pilot And Hot Standby Mode. Each Of The Processor Has 4 Mbytes Private Memory And 16 M Byte Primary Memory. All The Components Viz. Processor, Memory And Coupler Are Connected On The Xbus. The Secondary Memory Devices Like Disc, Magtape Devices, Streamers Etc. Are Connected On The Scsi Buses, Which Are Connected To Xbus Through Couplers. The Two Smms Are Connected Through Hdlc For Exchange Of Switch Over And Other Messages. The Smm Are Connected To Mis Token Ring Through Couplers For Interchange Of Message With Control Units. Various Terminals For Man Machine Communication And Alarm Couplers Are Connected To Xbus Through Communication Coupler.
Each Disk Has A Capacity Of 1.2 Giga Bytes And Both Of Them Are Connected To Active Smm. In The Normal Operation Data Is Read From And Written Into Both The Disks Simultaneously. But Whenever One Of Them Goes Faulty The Other Disk Is Available For Read And Writ Operation. The Contents Of One Disk Can Be Updated From Other By Command. Streamer Has A Capacity Of 525 Mbytes. It Is Used To Load System Data Into Disks And For Taking Backup Of The Disks. Two Magtape Drives Are Provided. Charge Account Data And Detailed Bill Data Re Transferred From Disk To Magtape For Further Processing In The Billing Center. Digital Recorded Announcement Card Is Also Equipped In The Smm Shelf. The Announcements Are Connected To Up To 2 Pcm Of First Smt From Where They Are Connected To Subscriber Or Circuit As Per Requirements. One Smm (Pilot And Standby) Is Provided At Each Ocb 283 Exchange. However The Smm Can Be Connected To Network Management Center (Nmc) For Remote Management.

Each Processing Unit Is An Sm Station On The Multiplex Mis And Is Built Around The Xbus. It Comprises The Following Boards.

O A Processor Board Acytg And A Memory Board Acmgs (Linked By A 32 Bit Address Bit Local Bus)

O A Pair Of Boards Acaja, Acajb Providing The Interface To The Mis Multiplex.

O An Acftd Line Coupler Board For Managing The Terminal Bus Interface

O Two Acbsg Boards For Managing The Interface With The Two Scsi Buses.

O A System Board Accsg.

O The Line Coupler Have Only One Active Port To A Processing Unit At A Given Time And Are Used To Manage The Synchronous/ Asynchronous Links At Rates Up To 19200 Bauds (Actuj Board), Synchronous Or High Speed Links (Acj64) And The Alarm Multiplexes (Acral2 Board)

(A) Acutg/ Acmgs Board

This Board Supports The Rtos Operating System And The Application Software Running In The Smm. This Board Is Called The Primary Processor And Is Denoted As Such In The Initialization Phase. It Is Built Around 68030 Processor Running At 16.7 Mhz With A 4M Of Private Dram And Local Bus Interface Representing An Addressing Capacity Of 4 Gbytes. Acmgs Board Is A 16 M Memory Board That Can Be Addressed On $ Gbytes By The Xbus Or The Local Bus.

(B) Accsg Board

This Board Restarts A Processing Unit That Has Been Reset To Zero Via The Accsg Front Panel V2 Switch Or Following An Xbus System Switchover. This Board Acts As The Locovar Controller For The Xbus Agent, Positioning Messages Via The Intersystem Board Link From The Active Side. This Board Is Built Around The Common Core System The Parts Specific Is Consists Of Circuits Managing The 1 Mbits/S Inter System Board Link And Managing The Distributed Switchover Functions.

(C) Acftd Board

This Board Supports The Input/ Output Processor Iop. Its Operating System Is Syspes. It Enables Handler Software To Perform Terminal Bus Line Management Functions. There Is A Handler For Each Protocol Implemented At Line Level. The Parts Specific To It Form The Terminal Bus Interface Built Around The Acbt Gate Array Circuit.

(D) Acbsg Board

This Board Includes Complete Scsi Bus Input/ Output Software Stored In Ram. There Is Also Prom Resident Software Controlling Scsi Access, Used When Initializing A Processing Unit. Each Acbsg Board Supports The Two Separate Scsi Buses. It Is Built Around A 68030 Processor Running At 16.7 Mhz, With 512 K Of Private Sram. And Two Scsi Bus Interfaces Based On 53C90A Circuits.

(E) Acaja/ Acajb Board

These Boards Handle The Mis Function. The Smm Incorporates A Secondary Line Coupler Cms. As Well As The Token Ring Management Function. It Supports The Mlsm And Mloc Software Modules.

(F) Acj64 Board

This Board Is Used For Synchronous Line Coupler Providing The Interface Between The Smm And The Telecommunication Maintenance Networks. 64 Kbits Digital Link Can Be Used In Which Case The Line Coupler Is Supported By This Board Handling Up To Four Links. A Secondary Acj64 Board Can Provide A Link Duplication Option Or Increase The Number Of Links, There Are Four Boards And 32 Asynchronous Links. This Board Is Built Around The 2652 Hdlc Controller.

(G) Acala Board

This Board Marshall Alarm From The Ae5V40 And Ae12V Converter Of Their Respective Sub Racks. A Third Acala Board Marshall Alarm For Announcement Machine/Streamer.

(H) Digital Announcement Machine Mpna

Automatic Announcements Are Provided In Ocb 283 At The Switching Matrix In The Form Of A Pcm Coming From A Mpna, Which Has Digital Recorded Voice Messages Stored In Pcbs. There Are Two Pcbs Icmpn2 (Ram, Volatile Memory Gives Pcm) And Icsmp (Eprom, Saves Voice Announcement Digital). These Are Two Cards And Are Suited In Smm Racks And The Announcement Are Carried By One Pcm Link From Icmpn 2 And Are Connected To One Smt; From Smt The Lrs Go To Smx. At Smx Its Time Slots Are Used For Getting The Respective Announcements. The Mpna Is Controlled By Small Hand Held Control Device Called Micro Terminal For Storing And Modifying Of Announcement Using Microphone/ Earphone.



















Bibliography
Company Profile



Bharat Sanchar Nigam Limited

Bharat Sanchar Nigam Limited (Bsnl) Is India'S Leading Telecommunications Provider And The Country'S Largest Public-Sector Firm. Bsnl Provides Local-Exchange Access And Domestic Long-Distance Services Through A Network Of More Than 45 Million Access Lines Covering Most Of India. It Also Offers Wireless Communications, Data And Internet Services, As Well As Business Voice And Data Services. The Company Is Still Controlled By The Government, As Is One Of India'S Other Large Phone Companies, Mahanagar Telephone Nigam Limited (Mtnl). Plans To Merge The Two Companies Have Been Discussed But Seem To Be On Hold.

Highlights

Bharat Sanchar Nigam Limited Has A Vast Reservoir Of Highly Skilled And
Experienced Work Force Of About 3,57,000 Personnel.

We Believe That Our Staff, Which Is One Of The Best Trained Manpower In The
Telecom Sector, Is Our Biggest Asset.

To Meet The Technological Challenges, Employees Are Trained For Technology
Up-Gradation, Modernization, Computerization Etc In Bsnl'S Training Centers
Spread Across Country.

To Apex Training Centers Of Bsnl I.E. Advance Level Telecom Trainingcenter
(Alttc) At Ghaziabad And Bharat Ratna Bhimrao Telecom Training Center
At Jabalpur Are Comparable To Any World Class Telecom Training Center.
Moreover, 43 Zonal Training Centers And A National Academy Of Telecom
Finance And Management Have Been Running For Several Years Now.

Different Curriculum Run In These Centers To Impart Technology Based Training,
Training For Attitudinal Change, Basic Educational And Skill Development
Program Etc.








Particulars Of The Organisation
Date Of Incorporation Incorporated On 15.9.2000, Vide Registration No. 55-107739, Dated The 15Th September, 2000 And Became Entitled To Commence Business With Effect From 19Th September, 2000.

The Company (Bsnl) Took Over The .Business Of Providing Telecom Services And Network Management Throughout The Country Except The Metro Cities Of Delhi And Mumbai Of The Erstwhile Service Providing Departments Of The Govt. Of India, I.E., The Departments Of Telecom Services And Telecom Operations W.E.F. 1.10.2000 Pursuant To An Mou Signed Between The Bsnl And The Govt. Of India.
Type Of Company Government Company Under Section 617 Of The Companies Act, 1956.
Administrative Ministry Govt. Of India, Ministry Of Communication And Information Technology, Department Of Telecommunications.
Details Of Disinvestments The Entire Share Capital Of The Company Is Held By The Govt. Of India
Shareholding Pattern Government Of India Is Holding 100% Of The Share Capital Of The Company
Listing With Stock Exchanges Not Applicable, As The Bsnl Is An Unlisted Company
Share Capital Authorised Capital – Rs.17,500 Crores, Divided Into 1,000,00,00,000[One Thousand Crores] Equity Shares Of Rs.10/- Each; And 750,00,00,000 [Seven Hundred And Fifty Crores] Preference Shares Of Rs.10/- Each
Paid Up Share Capital - Rs.5,000/- Crores Of Equity Shares And Rs.7,500/- Crores Of Preference Share Capital






Vision

To Become The Largest Telecom Service Provider In South East Asia.

Mission

- To Provide World Class State-Of-Art Technology Telecom Services On Demand At
Affordable Price.

- To Provide World Class Telecom Infrastructure To Develop Country'S Economy.

Profile Of The Company’S Business

A. Glimpses Of Main Services Offered

1. Basic And Limited Mobile Telephone Services
Bsnl Is The Leading Service Provider In The Country In The Basic Telephone Services. As Of Now More Than 35 Million Direct Exchange Lines & More Than 2.2.Million Telephones In The Limited Mobile Telephone Services Are Existing. Bsnl Has Provides A Number Of Attractive Tariff Packages & Plans Which Shall Further Strengthen Its Subscriber Base.

2. Cellular Mobile Telephone Services
Bsnl’S Gsm Technology Based Cellular Mobile Network Has Reached A Long Way, Covering More Than 6400 Towns, With A Subscriber Base Of Over 1.54 Crore As On 31St Jan. 2006 Out Of Which 1.16 Crore Cellular Telephones Are In The Prepaid Segment.

3. Internet Services
Bsnl Offers Dialup Internet Services To The Customers By Post-Paid Service With The Brand Name ‘Netone’, And Pre-Paid Service With The Brand Name ‘Sancharnet’. The Post-Paid Service Is A Cli Based Access Service, Currently Operational In 100 Cities. Sancharnet Is Available On Local Call Basis Throughout India To Isdn And Pstn Subscribers. The Internet Dhaba Scheme Of The Company Aims To Further Promote Internet Usage In Rural And Semi Urban Areas.
To Keep Pace With The Latest And Varied Value Added Services To Its Customers, Bsnl Uses Ip/Mpls Based Core To Offer World Class Ip Vpn Services. Mpls Based Vpns Is A Very Useful Service For Corporates, As It Reduces The Cost Involved As Well As The Complexity In Setting Up Vpns For Customers Networking. As On 31.03.2005, Your Company’S Total Internet Customer Base Was 17,98,089 And Total Internet Dhabas Were 4143. A Total Of 708594 Dial Up Internet Connections Have Been Given During 2004-2005, Against A Target Of 7 Lakhs. Bsnl Plans To Give 1215980 More Dial Up Connections During The Year 2005-06. As On 31.1.2006, There Were 2367404 Internet Subscribers Working In Bsnl Net Work.


4. Intelligent Network

Intelligent Network Services Is A Service That Incorporates Several Value Added Facilities, Thoroughly Designed To Save Time And Money, And Enhance Productivity. At Present, Your Company Offers Free Phone (Fph), Premium Rate Service (Prm), India Telephone Card (Itc), Account Card Calling (Acc), Virtual Private Network (Vpn), Universal Access Number (Uan) And Tele Voting In Services. With The Commissioning Of Five Numbers Of New Technology In Platforms (Four General Purpose And One Mass Calling) At Kolkata, Bangalore, Ahmedabad And Hyderabad, The India Telephone Card Facility And New Value Added Services Are Being Provided Throughout The Country. Activation Of These New In Platforms Had Increased The Sale Of Itc Cards Taking The Figure To Rs.265 Crores In 2004-05 Alone.

5. Broadband Services

Bsnl Has Launched Its Broadband Services Under The Brand Name ‘Dataone’ On 14/1/2005. This Offers Services Like High Speed Internet Access With Speed Ranging From 256 Kbps To 8 Mbps. Other Services Like Streaming Video, Video On Demand, Bandwidth On Demand Etc., Have Also Been Planned. As On 31.12.2005 , There Were More Than 356000 Broad Band Connection Provided By The Bsnl. There Are Plans To Give 2 Million And 3 Million Connections In 2006 And 2007 Respectively.

B.Development Of Rural Telecom Network

1. Rural Dels

As On 31.03.2005, In Bsnl’S Network, A Total Of 1.356 Crore Rural Telephone Connections Were Working. As On 31.1.2006, There Are 1.425 Crore Rural Telephones Working In Bsnl Network.

2.(A)Village Public Telephones (Vpts) & Rcps:-

Bsnl, In Its Unstinted Efforts To Make The Slogan ‘Connecting India’, A Reality, Had Provided Vpts In 5,18,992 Villages Up To 31.03.2005. The Company Entered Into An Agreement With Uso Fund For Expansion Of Rural Telecom Network By November 2007, By Providing Vpts In 66,822 Undisputed, Undisturbed, Accessible And Inhabited Villages Having Population More Than 100 As Per Census, 1991 In The Country. Bsnl Provided Vpts In 5,28,886 Villages Up To 31.01.2006. There Are Plans To Replace All Marr Vpts In The Country . As Of Now Total 123194 Marr Vpts Already Replaced In The Country By Bsnl. Bsnl Also Committed To Provide The Rural Community Phones As Per The Uso Fund Agreement. As Of Now Around 13713 Rcps Already Provided By Bsnl.

2(B) Public Telephones:-

There Are More Than 2 Million Pcos Working In The Bsnl Network Out Of Which Around 1 Million Pcos Are Having Std/Isd.

C. Network Management
Bsnl Is Committed To Provide A Robust State Of The Art Infrastructure That Will Provide Stable And Superior Services To Its Customers. Accordingly, The Mlln Network Covering More Than 200 Cities Was Made Operational In May 2004. Since Then, About 22000 Circuits Have Been Provided On This Network. This Has Provided High Level Of Stability To The Leased Circuits And Capability To Offer N X 64 Kbps Circuits. Keeping In View The Growing Demand Of Leased Circuits, The Network Is Being Expanded To Cover About 50 More Locations And Additional Capacity At Many Existing Locations Is Also Being Provided.

To Improve The Operational Efficiency Of Ccs 7 Signaling, Stand-Alone Signaling Transfer Point (Sstp) Equipment Is Being Procured. This Will Also Enable The Company To Measure Signaling Traffic Of Other Operators, Who Are Using Its Signaling Network For Exchanging Messages, Specially With Regard To Cellular Services. Bsnl Has More Than 4.7 Lakhs Route Kilometers Of Optical Fibre Network In The Country & Has Installed Capacity More Than 6.4 Million Lines For The Tax Meant For The Std/Isd Network.


D. Setting Up Ku Band Vsat Network
As Regards The Ku Band Vsat Network Equipment, The Hub Of This Network Is Being Set Up At Bangalore, The Equipment Has Been Installed And Expected To Be Commissioned Shortly. This Will Help Your Company, To Become A Service Provider With All Types Of Media Equipment I.E. Ofc, Microwave And Satellite For Provision Of Bandwidth, This Will Also Enable The Company To Offer Composite Solutions To Its Customers.

E. Policy On Transmission Network Maintenance
Telecom Circles Have Large Transmission Networks. To Improve The Maintenance Of Transmission Network, Guidelines For Route Parties And Vehicles Have Been Formalised. Telecom Territorial Circles Are Also Being Connected With Computerised Network For Booking Of Transmission System Faults, With A View To Improve Follow Up And Faster Restoration Of Faults.

F. Annual Maintenance Contracts For Switching System & Wll
Comprehensive Amc, Which Includes Hardware And Software Maintenance And Upgrade, Has Been Arranged With The Respective Equipment Suppliers. Initial Feedback Suggests That, As A Result Of Preventive And Corrective Maintenance Support, The Performance Of Switches Is Improving. Difficulties In Entering Into Amc With Rural Wll Equipments Suppliers Have Been Resolved And Procedures Streamlined So That Adequate Maintenance Support Becomes Available. As A Result, The Performance Of Wll Network Is Improving. Amc Arrangements Have Also Been Made With Suppliers Of Fwts And Hand Held Terminals.
G. Computerisation
Implementation Of Inter Operator Billing And Accounting System (Iobas) Has Been Completed. Your Company Plans To Provide Cdr Based Customer Care And Convergent Billing System. This Will Help Company In Providing Effective And Efficient Billing & Customer Care Solutions For Its Fixed Line Subscribers. It Envisages Building Of Country Wide Intranet To Reduce The Cost Of Operation, Increase Realization, Stop Leakage Of Revenue And Minimize Frauds, Besides Providing Round The Clock Best Customer Care Services To The Company’S Subscribers.

Call Center Facility Has Been Introduced For 71 Ssas, Which Is A Single Point Approach For Addressing All Customer Needs Cum Grievances. Web Based Public Grievance Management System Has Been Implemented For Speedy Disposal And Monitoring Of Public Grievances. Web Based Inventory Management Package Has Also Been Introduced, Through Which, Material Management Functions Are Being Computerized Gradually In Different Circles. Online Mobile Bill Viewing Facility Has Been Made Available To All Cell One Mobile Customers (All States) Through Company’S Portal (Http://Bsnl.In). Duplicate Telephone Bill Viewing Facility For Landline Telephone Has Also Been Made Available At Many Places Through Websites Of Respective Telecom Circles.

H. Obligations

1. Towards Customers And Dealers
To Provide Prompt, Courteous And Efficient Service And Quality Of Products/Services At Fair And Reasonable Services.
2. Towards Employees
? Develop Their Capability And Advancement Through Appropriate Training And Career Planning
? Expeditious Redressed Of Grievances
? Fair Dealings With Recognized Representatives Of Employees In Pursuance Of Healthy Trade Union Practices And Sound Personnel Policies






3. Towards The Society –Corporate Social Responsibilities
Corporate Social Responsibilities
Bsnl Is Committed To Provide Quality Telecom Services At Affordable Price To The Citizens Of The Remotest Part Of The Country. Bsnl Is Making All Effort To Ensure That The Main Objectives Of The New Telecom Policy 1999 (Salient Points Indicated Below) Are Achieved:
Access To Telecommunications Is Of Utmost Importance For Achievement Of The Country'S Social And Economic Goals. Availability Of Affordable And Effective Communications For The Citizens Is At The Core Of The Vision And Goal Of The New Telecom Policy 1999.
Strive To Provide A Balance Between The Provision Of Universal Service To All Uncovered Areas, Including The Rural Areas, And The Provision Of High-Level Services Capable Of Meeting The Needs Of The Country'S Economy Encourage Development Of Telecommunication Facilities In Remote, Hilly And Tribal Areas Of The Country;
Transform In A Time Bound Manner, The Telecommunications Sector To A Greater Competitive Environment In Both Urban And Rural Areas Providing Equal Opportunities And Level Playing Field For All Players
I. Assistance During Natural Calamities

Bsnl Always Remains Awake Of Its Responsibility As A Corporate Citizen. When The Destructive Tsunami Waves Struck The Indian Shores, Bsnl Company Swung Into Action Immediately For Providing Relief To Those Affected In The Coastal Areas. Communication Networks At The Coastal Areas Of Tamil Nadu, Kerala And The Andaman And Nicobar Islands – Worst Hit In The Tsunami - Were Promptly Restored Within The Shortest Possible Time. Bsnl Along With The Employees Contributed An Amount Of Rs. 2,207 Lakhs To The Prime Minister’S Relief Fund. Telephone Services Were Restored In Record Time In The Flood-Hit Areas Of Gujarat And Maharashtra.








Ocb 283

Introduction

Telecommunication Networks Are Constantly Changing. The Rapid Growth Of The Digital Network, Mobile Network And Intelligent Network And The Proliferation Of New Services Being Constantly Offered To Subscriber Means That Equipment Must Be Continuously Adapted To New Requirements. All The New Switching Systems Are Based On Stored Program Control Concept. The Call Processing Programmes Are Distributed Over Different Control Organs Of The System And Are Stored In Rom/Ram Of The Units Processor In The Control Units By Using The Programme And Data Stored In Unit Rom/Ram Process And Handle Calls. Handling Or Processing A Call Means To Ultimately Establish A Connection In Between Incoming And Outgoing Ends. Depending On The System The Name And Architecture Of Control Units And Switch May Change But Basic Criterion For Switching More Or Less Remains Same.
The Alcatel 1000E10 Exchange Also Known By Its Other Name Ocb283 Is Designed To Cater For Evolving Networks And The Need To Rationalize Equipment Operation. Its Modular Architecture Means That New Services Can Be Added And Processing Capacity Can Be Increased Without Interrupting Operation Of The Exchange. Ocb 283 Is A Digital Switching System Which Supports A Variety Of Communication Needs Like Basic Telephony, Isdn, Interface To Mobile Communication, Data Communication Etc. This System Has Been Developed By Alcatel Of France And Therefore Has Many Similarities To Its Predecessor E-10. The First Ocb283 Exchange Of R11 Version Came To India In 1993. At Present R23 And R24 Are Also Being Supplied. The Basic Architecture Remaining Same, More Facilities To Subscriber And Administration Are Supported By Later Versions.

Features Of The System

I. It Is A Digital Switching System With Single ‘T’ Stage Switch. A Maximum Of 2048 Pcms Can Be Connected.

Ii. It Supports Both Analogue And Digital Subscriber.

Iii. The System Supports All The Existing Signaling System Like Decadic, Mf, Cas And Also Ccitt#7 Signaling System.

Iv. It Provides Telephony, Isdn, Data Communication, Cellular Radio And Other Value Added Services.
V. The System Has ‘Auto Recovery’ Feature. When A Serious Fault Occur In A Control Unit, It Gives A Message To Smm(Operation & Maintenance Unit). The Smm Puts This Unit Out Of Service, Loads The Software Of Faulty Unit In A Backup Unit And Bring It Into Service. Diagnostic Programmes Are Run On The Faulty System And Diagnostics Are Printed On The Terminal.

Vi. Ocb283 Has Double Remoting Facility. Subscriber Access Unit Csnd Can Be Placed At A Remote Place And Connected To The Main Exchange Through Pcm Links. Further Line Concentrators Are Placed At A Remote Location And Connected To The Csnl Or Csnd Through Pcms. This Special Feature Can Meet Entire Range Of Necessities Like Urban, Semi-Urban And Rural.

Vii. Various Units Of Ocb283 System Are Connected Over Token Rings. This Enables Fast Exchange Of Information And Avoid Complicated Links And Wiring Between Various Units.

Viii. The Charge Accounts Of The Subscribers Are Automatically Saved On The Disc, Once In A Day. This Avoids Loss Of Revenue In Case Of Total Power Supply/ Battery Failure Or Any Other Type Of Exchange Failure.

Ix. Traffic Handling Capacity Of The System Is Very Huge. It Can Handle 8,00,000 Bhca And 25,000 Erlangs Of Traffic. Depending On The Traffic, A Maximum Of 2,00,000 Subscribers Or 60,000 Circuits Can Be Connected.

X. The Exchange Can Be Managed Either Locally Or Through Nmc Of 64Kbps Link.

Xi. The Ocb283 System Is Made Up Of Only 35 Different Type Of Cards. This Excludes Cards Required For Csn. Because Of This The Number Of Spare Cards Required For Maintenance Purpose, Are Drastically Reduced.

Xii. All The Control Units Are Implemented Are Implemented On The Same Type Of Hardware. This Is Called A Station. Depending On The Requirement Of Processing Capacity, Software Of Either One Or Several Control Units Can Be Located On The Same Station. For All These Control Units, Only One Backup Station Is Provided, Enabling ‘Automatic Recovery’ In Case Of Fault.

Xiii. The System Has Very Modular Structure. The Expansion Can Be Carried Out Very Easily By Adding Necessary Hardware & Software.
Xiv. The Smm(O&M Units) Are Duplicated, With One Active And Other Hot Standby. In Case Of Faults, The Switchover Takes Place Automatically. Moreover, Discs Are Also Connected To Both The Smms, There Is No Necessity Of Changing Of Cables From One To Another.

Xv. The Hard Disc Is Very Small In Size, Compact And Maintenance Free. It Has A Very Huge Memory Capacity Of 1.2Gb. The Detail Billing Data Are Regularly Saved In These Discs Itself, From There It Can Be Transferred To The Magnetic Tapes For The Purpose Of Processing.

Xvi. There Is No Fixed Rack And Rigid Suite Configuration In This System. It Provides Greater Flexibility And Adjustment In The Available Space.

Xvii. This System Can Work At A Temperature 5°C To 45°C, Though The Optimum Temperature To Work Is 22°C.




Subscriber Facilities Provided By Ocb283

It Provides A Large Number Of Subscriber Facilities. Some Facilities Are Available To Only Digital Subscriber And As Such They Can Not Be Availed By Analogue Subscribers. To Avail These Facilities Subscriber Number Are Given Special Categories By Man Machine Commands.
I. A Line Can Be Made Only Outgoing And Incoming.

Ii. Immediate Hotline Facility – The Subscriber Is Connected To Another Predetermined Subscriber On Lifting The Handset, Without Dialing Any Number.

Iii. Delay Hotline Facility – When Subscriber Lifts The Handset, Dial Tone Is Provided, He Can Dial Any Number. If He Does Not Dial A Number, Within A Predetermined Time, He Is Connected To Predetermined Number.

Iv. Abbreviated Dialing – The Subscriber Can Record A Short Code And Its Corresponding Full Number In The Memory. Later To Dial This Number He Has To Dial Only Short Code Of That Number.

V. Call Waiting Indication – When A Subscriber Is Engaged In Conversation And If Getting An Incoming Call, An Indication Is Given In The Form Of A Tone. Hearing This, The Subscriber Has Option, Either To Hold The Subscriber In Conversation And Attend The Waiting Call Or To Disconnect This Subscriber And Attend To The Waiting Call. In The Former Case He Can Revert Back To The Earlier Subscriber.

Vi. Call Forwarding – When Provided, Incoming Calls To The Subscriber Gets Transferred To The Number Mentioned By The Subscriber While Activating The Facility. This Facility Is Especially Very Useful For Those Person Who Are Always On Move.

Vii. Conference Between 4 Subscribers – The Subscriber A & B While In Conversation, Can Include Two More Subscriber By Pressing ‘* Button’ And Dialing Their Numbers.

Viii. Automatic Call Back On Busy – If This Facility Is Activated And If The Called Subscriber Is Found Busy, The Calling Subscriber Simply Replaces The Receiver. The System Keeps Watch On The Called Subscriber And When It Becomes Free, A Ring Is Given To Both The Subscribers. On Lifting They Can Talk To Each Other.

Ix. Priority Lines – Calls From These Lines Are Processed And Put Through Even When The Number Of Free Channels Are Within A Threshold Or When The System Is Operating In Catastrophic Mode.

X. Malicious Call Identification – When This Category Is Given To A Subscriber, The Number Of Calling Subscriber, The Number Of Calling Subscriber To This Number Is Printed On The Terminal Or Displayed On The Caller Identification Instrument.

Xi. 12 Or 16Khz Meter Pulses – The System Can Send 12 Or 16Khz Meter Pulses On The Subscriber Line For The Operating Of The Home Meter.

Xii. Battery Reversal – The System Extends Battery Reversal When Called Subscriber Answers. This Is Useful In Case Of Ccbs( Coin Collection Box ).

Xiii. Detailed Billing – The System Provides Detail Bills Given Details Of Date, Time, Metered Units Etc.

Xiv. Absent Subscriber Service – When Activated, The Incoming Calls Are Diverted To Absent Subscriber Service For Suitable Instruction Or Information.
Xv. It Provides 64 Kb/S Digital Connectivity Between Two Subscribers For Data Communication.

Xvi. This System Provides Facsimile (Fax) Services And Videotext Services Also.

Xvii. This System Also Provides The Facility For Restriction Of The Display Of Calling Subscriber Number On Called Subscriber’S Telephone Terminal Or Caller Id Set. To Avail This Facility The Subscriber Has To Be Given A Category Like Some Vvips Or Some Beurocrats.

Xviii. User To User Signaling – The System Permits Of Mini Messages Between Calling And Called Subscribers During Call Setup And Ringing Phase.

Xix. Terminal Portability During The Call – A Subscriber (Calling Subscriber As Well As Called Subscriber) Can Unplug Telephone Instrument, Carry It To Some Other Place Or Room And Resume The Call Within 3 Minutes

Xx. Listing Of Unanswered Calls – The Number Of Calling Subscribers, Who Calls During The Absence Of Called Subscriber, Are Recorded In Called Subscriber’S Terminal. The Called Subscriber Than Check Up These Numbers And Call Them Back, If He So Wishes.

Xxi. This System Provides Two Type Of Isdn Connections To The Digital Subscriber, One Is Of 2 B + D Line (2 Voice Channels Of 64Kbps & I Data Channel Of 16Kbps) Type And Other Is Of 30 B + D Line (30 Voice Channels Of 64Kbps & 1 Data Channel Of 16Kbps) Type.














Common Channel Signaling No. 7 (Ccs#7)

Introduction

The Latest Signaling Now Being Implemented Worldwide Is Common Channel Signaling Or Also Called Ccs#7 Signaling. This Type Of Signaling Is Essential For The Setting Up Of The Isdn (Intelligent Services Digital Networks) Services.
In This Type Of Signaling The Signaling Information Is Sent From One Exchange To Other Exchange (Called Signaling Points Sp) In The Form Of Messages Coded In Binary Form, Which Is Understandable By The Intelligent Devices Available At Both The Ends Means In Both The Exchanges. The Ccitt (Consultative Committee On International Telecom Treaty) Organization Has Recommended A Standard Protocol Called Ccitt#7 Signaling. The Signaling Message Travels Over A Single Time Slot Of The Pcm Connecting The Two Exchange (Signaling Point Sp). This Time Slot Is Called Common Channel For Signaling, Hence The Name Common Channel Signaling. The Message Over This Common Channel Carry All Relevant Data For Any Of The Other Time Slots Or Circuits Which Carry Voice Or Subscriber Data. The Channels For Subscriber Are Called Voice Channels.

Common Channel Signaling

Voice Channels







Common Channel
For Signaling
.




Signaling Points





The Ocb283 Exchange Uses Common Channel Signaling Between Its Csn & The Common Control Equipment Also. Signaling Is Often Referred To As Glue, Which Holds A Network Together. It Provides The Ability To Transfer Information Between Subscribers, Within Networks & Between Subscribers And Networks. Signaling Is The Lifeblood, The Vitalizing Influence Of Telecommunication Networks. Without Signaling, Networks Are Inert. By Providing Effective Signaling System, A Network Is Transformed Into A Tremendously Powerful Medium Through Which Subscriber Can Communicate With Each Other Using A Range Of Telecommunication Services. Old Signaling System That Was Simple Mechanisms For Transferring Basic Information Are Being Replaced By Efficient Data Transfer Highways. It Is Signaling That Provides The Ability For Subscriber To Indicate To The Exchange That A Call Is Required. It Also Allows The Called Subscriber To Be Identified E.B. By Transferring The Telephone Number Dialed By Calling Subscriber.

It Allows The Transfer Of Information Between Exchanges In The Network To Establish And Release The Call. It Transforms The Foundation Of Network Into An Active Entity That Can Provide The Required Services To The Subscribers. It Consists Of The Instructions, Which Originate From The Telephone User On The Form Of Lifting The Handset In Order To Make A Call, The Transmission Of Dial Pulses Generated By Operating A Dial & Replacing A Receiver At The End Of The Call. Instructions Are Also Signaled By Exchange In The Form Of Dial Tone, Ringing Tone Etc., To Indicate The Progress Of The Call. In Addition Inter Exchange Signaling Takes Place Between A Call Is Set-Up, To Control Exchange Operations & & Check On Circuit Availability.

Types Of Signaling

Telephony Started With The Invention Of Magneto Telephones, Which Uses A Magnet To Generate The Ringing Current, The Only Signal Sent Over A Dedicated Time Between Two Subscribers. As The Switching Technology Has Undergone A Vast Change From Manual Switching To Digital Switching, The Inter Exchange Signaling Techniques Have Also Progressively Changed From Loop No Loop Signaling To Mf Signaling & Finally Digital Signaling. The First Digital Switching Developed Was Channel Associated Signaling In Which The Signaling Information Is Conveyed On A Separate Channel, Which Is Rigidly Associated Channel. The Utilization Of Such A Dedicated Channel For Each Speech Channel Is Highly Inefficient, As It Remains Idle During The Entire Speech Phase. Hence A New Signaling System Was Developed Which Is Capable Of Providing All New Services & Its Internationally Standardized Is Known As Common Channel Signaling.

Signaling In Pulse Code Modulation

Pulse Code Modulation (Pcm) Is A Method Of Converting Information From An Analog Form To A Digital Form For Transfer Over A Digital Transmission Systems, The Technique Involves Sampling The Analogue Waveform And Coded The Result In The Digital Format. Successive Sampling Allows The Analogue Waveform To Be Represented By A Series Of 8-Bit Code. 8 Bit Codes Form Numerous Speech Channels Are Assembled Into Blocks For Transmission By Inserting Into Time Slots. The Technique Is Called Time Division Multiplexing (Tdm).

The Bandwidth Required To Transmit Signal Is Much Less Than That For Speech, So That Signaling For Several Speech Channels In A Pcm System Can Be Handled By A Small Portion Of The Bandwidth. The Signaling Capacity Can Be Used For Cas Or Ccs, The Means Of Identifying To Which Speech Channel A Particular Signal Refers Is To Divide The Signaling Capacity Into Dedicated Bit Locations. Signal Pertinent To A Particular Speech Path Are Always Transmitted In Signaling Bit Locations Dedicated To That Speech Channel. The Means Of Conveying Ccs Is To Compound The Signaling Capacity Into A Signaling Channel That Is Available As And When Required.

The Ccitt Has Defined Pcm Standards For 30 Channel And 24 Channel Systems. The Capacity Available For Signaling In These Two Standards Is Different As A Result Of Differing Constraints Applied By The Pcm Standard.

In 30 Channel Pcm Systems, The 8-Bit Code Relating To 30 Speech Channels Are Time Divisioned Multiplexed Into A Frame. Each 8-Bit Code Is Inserted Into A Time Slot Within The Frame. Time Slot 0 Is Used For Alignment; Time Slots 1-15 And 17-31 Are Used For Encoded Speech Related To 30 Channels. The Slot 16 Is Dedicated For The Use Of Signaling.

The Tenet Of Cas System Is That Dedicated Signaling Capacity Is Available For Each Speech Circuit. This Is Achieved In 30 Channel Pcm Systems By Allocating 4 Bits In Each 16-Frame Multi-Frame To Signaling For Each Speech Channel.




Frame
Multi-Frame
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


Speech Channel
Time Slot
Frame
- 1 2 3 15 - 17 28 29 30
0
1 2 3 15 16 17 29 30 31



Bits
1 2 3 4 5 6 7 8

Fig. : Frame Structure Of 30-Channel Pcm System

Principle Of Ccs
In Common Channel Signaling Systems, The Physical Tie Between The Signaling Path And Traffic Circuit Is Removed. All Signaling Transfer Relating To A Transmission Link Takes Place Over A Dedicated Signaling Channel. Hence, A Common Signaling Channel Handles The Transfer Of Signaling Information For Numerous Traffic Circuits. Signaling Capacity Is Not Reserved For Each Circuit, But Signaling Capacity Is Allocated Dynamically As When Required. Fig. Shows The Concept Of Ccs For Both Access And Inter-Exchange Signaling. Exchange A And B Are Connected By Numerous Speech Circuits, Denoted By Solid Lines. All The Signaling That Relates To The Speech Circuit Is Transferred Between The Exchanges Using The Common Signaling Path (Denoted By Dotted Lines). The Common Signaling Path Can Be Regarded As A Pipe Between Two Exchanges, Typically Operating At 64 Kbps, Into Which All Signaling Information Is Funneled. Similarly, All Signaling Information Pertaining To The Speech Circuit Between Each Subscriber And Exchange A Is Transferred Via The Access-Signaling Channel.





Speech





Fig. : Ccs Signaling : Associated Mode Of Operation



The Transfer Of Signaling Information Is Achieved By Sending Message Down The Common-Signaling Path. The Use Of Message In Ccs Systems Opens Up A Whole Range Of Flexibility That Is Not Present In A Cas System. Instead Of Being Limited To A Small Number Of Meanings For Signals Messages Can Be Designed To Cover Multitude Of Situations And Services.

The Signaling Activity When Setting Up & Releasing A Circuit Is High; However On An Average The Signaling Activity For A Circuit Is Low Because There Are No Signaling When The Calls Are Not Being Made & During The Conversation Phase Of The Call. Hence, A Single Ccs Channel Can Be Used To Use Numerous Traffic Circuits. The Theoretical Limit Of The Number Of Traffic Circuits Handled By Ccs Channel Is Very High, But A Typical Practical Value Is 2000Traffic Circuits. The Picture Become More Complex When Non-Circuit Related Signaling Activity Is Taken Into Account. Non Circuit Related Signaling Can Be Intermittent (E.G. It Is Used During Call Establishment To Interrogate A Database) Or It Can Exhibit A High Signaling Activity (E.G. If It Is Used To Transfer A Large Amount Of Management Data Between Nodes In A Network).

Mode Of Operation

Ccs System Can Operate In A Number Of Modes With In Telecommunication Network. An Exchange In Telecomm Network That Operates Ccs Is Termed As A ‘Signaling Point’. Any Two Signaling Points With The Possibility Of Signaling Communication Are Said To Have ‘Signaling Relation’. The Realization Of The Signaling Relation Is By Sending Signaling Messages Between The Two Exchanges. The Path Taken By The Signaling Messages Is Determined By The Mode Of Operation. Hence The Modes Of Operation Determine Hoe Signaling Messages Routed Between Signaling Points. The Modes Of Operation Can Be ‘Associated’, ‘Non-Associated’, Or ‘Quasi-Associated’.

In The Associated Mode Of Operation, The Signaling Messages Transferred Over Transmission Link Directly Connecting The Relevant Signaling Points As Shown In The Above Figure And In The Below Figure Also. In Quassi-Associated Modes Of Signaling, The Messages Pertinent To A Particular Signaling Relation Are Not Transferred Over Transmission Links Directly Connecting The Relevant Signaling Points. Instead, The Messages Are Transferred Using Intermediate Signaling Points. In This Mode Of Signaling, The Path Taken By The Messages Through The Signaling Network Is Predetermined By Information Assigned By The Network.

Exchange A & B Have A Signaling Relation And Are Interconnected By Speech Paths. However The Signaling Path Used To Implement The Signaling Relation Is Via Exchange C And Not Directly Between A & B. In The Case Of Failure Of The A-B Signaling Link, The A-C-B Signaling Can Be Used To Control The Speech Path Between Exchanges A & B. Quassi-Associated Modes Of Operation Illustrate Great Flexibility And Powerful Nature Of Ccs System.






Speech
Path










Signaling Transfer

Fig. : Quassi-Associated Mode Of Operation

Requirements Of Ccs

The Ccs Has The Following Additional Requirements Introduced In Three Areas:
(I) Reliability And Security
(Ii) Speech Continuity
(Iii) Processing Overhead

1. A Signaling Channel Carried On A 64Kbps Link Has The Practical Capacity To Control Approximately 2000 Traffic Circuits. Hence The Failure Of An Inter Exchange Signaling Link Would Cause The Loss Of A Significant Amount Of Speech Traffic. For Access Signaling, The Loss Of The Signaling Link Would Means Isolation Of The Subscriber From The Local Exchange. It Is Therefore Essential To Take Exceptional Precautions To Avoid Such Losses.

2. Signaling Security Can Be Improved By Developing The Signaling Network Itself. In The Access Network, It Is Possible To Provide Two Signaling Links To A Subscriber (Preferably On Physically Diverse Transmission Links) & To Switch All Traffic To One Link When Other Links Interrupted. Similar Arrangements Can Be Made For Inter Exchange Signaling With Automatic Reconfiguration Of Signaling Paths, Even Via Different Exchanges To Maintain A Signaling Continuity In The Event Of Failure Of A Signaling Link.

3. The Unavailability Of Signaling Communication Between Two Exchanges Is Specified As A Maximum Of 10 Minutes Per Year.

4. Cas System That Use The Speech Path To Transfer Signaling Information Provide The Inherent Feature Of Checking The Continuity Of Speech Path Being Established Before Conversation Begins. If Continuity Is Not Achieved, The Signaling Transfer Is Not Successful The Call Is Aborted Or A Further Attempt Is Made To Connect Call. The Inherent Continuity Checks Is Absent In Ccs Systems, Owing To Separation Of Speech & Signaling Paths If Considered Desirable, Separate Speech Checks Can Be Provided.

5. The Flexible Manner In Which Ccs Systems Are Structured & The Implementation Of The Complex Network Feature Mean That Extra Processing Is Necessary To Operate Ccs. Even The Inherent Concept Of Funneling All Signaling On A Transmission Link Into Ccs Means That Messages Must Be Analyzed To Determine Which Circuit They Referred . However, This Extra Processing Overhead Is More Than Out Weighted By The Benefit Of Ccs Systems.

Salient Features Of Ccs

(I) Signaling Information For A Number Of Circuits Is Sent On A Single Channel. The Physical Tie Between The Signaling Path & Traffic Circuit Is Removed. All Signaling Transfer Relating To A Transmission Link Takes Place Over A Dedicated Signaling Channel. Hence, It Handles Information For Numerous Traffic Circuits.

(Ii) Signaling Is In The Form Of Data A Data Channel Operating At 64 Kbits/Sec. Rate Is Provided.

(Iii) Signaling Is Very Fast All The Required Digits Can Be Simultaneously Sent On The Data In The Form Of Message.

(Iv) It Can Also Work On 4.8Kbits/Sec. Link By Providing Modems.

(V) It Is Very Economical Between Exchanges Where Large Number Of Circuits Are Provided.

(Vi) It Can Cater For All New Services Such As Videotext, Data Communication, Facsimile And Isdn Services Etc.

(Vii) In Cas Systems, Signaling Capacity Is Dedicated To A Traffic Circuit. Limitations Exist On When Signals Can Be Sent, Depending On The Status Of The Call. For Example It Is Not Possible To Send Voice Frequency Signals During The Speech Phase Of A Telephone Call In Some Cas System, Unless Special Measures Are Taken (E.G. Provision Of Filter) Because Subscriber Are Able To Hear Tones. However Within These Constraints, It Is Not Possible To Send Signals Instantaneously. In Ccs Each Message Taken Up Whole Of The Signaling Channel For A Short Length Of Time. It Is Possible For An Exchange To Send Two Messages Relating To Two Circuits From A Transmission Link Exactly At A Same Time, Each May Take A Few Microseconds To Transmit. For This Reasons ‘Buffers Are Provided At Each End Of Ccs Link To Store Each Message Until The Link Becomes Available. As Messages Are Generated By An Exchange, They Are Stored In A Buffer And Transmitted In A Specified Order. When There Are No Messages To Transmit, There Is A Need To Maintain Synchronization Of The Signaling Channel Between The Two Exchanges. This Is Achieved By Continuously Transferring Synchronization Information Until A New Message Is Ready For Transmission.

(Viii) Ccs Systems Are Specified In Terms Of “Format” And “Procedures”. The Specification Of The Formats Defines The Structure Of Messages Used And Meaning Of Each Field Within The Message. The Specification Of The Procedures Defines The Logical Sequence In Which Messages Can Be Sent. The Procedures Of Ccs Circuit-Related Systems Are Closely Linked To Functions Within Exchanges That Control The Setup And Release Outgoing Calls. There Is Therefore A Close Relationship Between Ccs Procedures And Exchange Call Control And A Major Element In Defining Ccs Systems Is The Need To Achieve An Optimum Between These Factors.

(Ix) The Drive To Provide An Unrestricted Communication Capability Between Exchange Procedures Eliminates Per Circuit. Cas System But By Funneling All Signaling Information Into A Single Common Channel, Only One Signaling Termination Cost Is Incurred For Each Transmission Link. These Are Cost Penalties For Ccs Systems; The Messages Received By An Exchange Have To Be Analyzed Resulting In Processing Overheads. However These Are Covered By Increased Scope Of Inter Processor Activity.

(X) Cas System Posses Limited Information Transfer Capability To :
A) The Restricted Number Of Conditions That Can Be Applied (E.G. The Limited Variations That Can Be Applied To A Dc Loop Or Limited Number Of Frequency Combinations That Can Be Implemented In A Voice Frequency System)
B) The Limited Number Of Opportunity To Transfer Signals (E.G. It Is Not Possible To Transmit Voice Frequency Signals During The Conversation Phase Of Call Without Inconveniencing The Subscriber Or Taking Special Measures.
Neither Of These Restrictions Apply To Ccs The Flexible Message Based Approach Allows A Vast Range Of Information To Be Defined And The Information Can Be Sent During Any Stage Of A Call. Hence, The Reperoire Of Ccs Is Far Greater Than Channel Associated Versions And Messaged Can Be Transferred At Any Stage Of A Call Without Affecting The Calling And Called Subscriber.

(Xi) Ccs System Transfer Signals Very Quickly. A Message Used To Establish A Call In A Ccs System Can Contains All The Address Digits In An Information Field.

(Xii) Techniques Used In Modern Ccs Systems Can Be Further Improve The Flexibility Proved To Subscriber. ‘User-To-User’ Signaling Is A Technique Whereby Messages Can Be Transferred Form One Subscriber To Another Without Undergoing A Full Analysis A Full Analysis At Each Exchange In Network. Similarly ‘End-To-End’ Signaling Allows Exchanges To Transfer Information To Each Other Without Intermediate Exchanges Having To Fully Process The Messages.

(Xiii) One Of The Problems That Prompted The Development Of Ccs System Was ‘Speech Clipping’ In The International Network. In Some Cas Systems, It Is Necessary To Split The Speech Path During Call Set-Up To Avoid Tones Being Heard By The Calling Subscriber. This Results In A Slow Return Of The Answer Signal And, If The Called Subscriber Starts Speaking Immediately After Answer, Then The First Part Of The Statement Called By The Subscriber Is Lost. As The First Statement Is Usually The Identity Of The Called Subscriber, This Causes A Great Deal Of Confusion And Inconvenience. Ccs System Avoids This Problem By Transferring The Answer Signal Quickly.

(Xiv) As A Result Of The Processing Ability Of Ccs System, A High Degree Of Reliability Can Be Applied With A Resulting High Confidence In The Transfer Of Uncorrupted Information In The Case Of An Intermediate Exchange Failure, Re-Routing Can Takes Place Within The Signaling Network, Enabling Signaling Transferred To Be Continued.


Level Structure Of Ccs#7

Ccs#7 Is Optimized For Use In Digital Environment, But It Can Be Used In Any Transmission Medium. Ccs Is Highly Flexible, Facilitates The Evolutionary Process And Supports A Variety Of Services And Network Features. These Attribute Result From An Early Decision To Specify Ccs In A 4 Layer Structure A Illustrated In A Fig.

A Prime Objective When Formulating The Design Of Ccs Channel Was To Ensure That The Signaling System Flexibly Handle The Requirements For Circuit-Related Applications. These Applications Include Telephones And Circuit-Switched Data (I.E. Data Using Circuit Within Transmission Links In A Similar Way To Telephone Calls). The Functions Performed By The Four Layers Are Described.

Level 1- Physical Function.

Any Node With The Capability Of Handling Ccs Is Termed As ‘Signaling Point’. The Direct Interconnection Of Two Signaling Points With Ccs#7 Uses One Or More Signaling Links. Early Version Will Use Variation Of The Installed Copper Local Loops For Connection Between The Local Exchange And The Subscriber Premises; Later Version Will Undoubtedly Use Fiber Optics Technology. Level 1 Of The 4 Level Structures Defines The Physical And Electrical Functional Characteristics Of The Signaling Links. Defining Such Characteristics With In Level Means That Rest Of The Signaling System Can Be Independent Of The Transmission Medium Adopted. By Keeping The Interface Between Levels 1 & 2 Constant Any Changes Within Level 1 Do Not Affect The Higher Levels. In A Digital Environment The Usual Physical Link Is A 64Kbits/Sec. Channel. This Is Typically Within A Digital Transmission System Using Pulse Code Modulation. However Other Type Of Links (Including Analogue) Can Be Used Without Affecting The Level 2 To 4.



Level 2-Signaling Link Function.

Level 2 Defines The Function That Is Relevant To An Individual Signaling Link, Including Error Control And Link Monitoring. Thus Level 2 Is Responsible For The Reliable Transfer Of Signaling Information Between Two Directly Connected Signaling Point. If Error Occurs During Transmission Of The Signaling Information, It Is The Responsibility Of Level 2 To Invoke Procedures To Correct The Errors Such Characteristics Can Be Optimized Without Affecting The Rest Of Signaling Systems, Provided That The Interface To Level 1 & 3 Remains Constant This Function Is Achieved By

A) Initial Link Alignment, Synchronization And Proving To Ensure That The Link Error
Rate Performance Is Satisfactory.

B) Continuous Link Error Rate By Monitoring By Sending Fill In Signal Units During
The Idle Time.

C) Error Detection By Means Of The Fcs Field In Each Signal Units And Error Correction By Retransmission Of The Message Signal Unit.
The Above Measures Ensure That There Are Not More Than 1 In 1010 Signal Units With Undetected Errors And Not More Than 1 In 107 Lost Signal Units.

Level 3- Signaling Network Functions

These Functions That Are Common To More Than One Signaling Link I.E. Signaling Network Functions Are Defined In Level 3: This Includes “Message Handling” Function & “Signaling Network Management” Function. When A Message Is Transferred Between The Exchanges, There Are Usually Several Routes The Message Can Take, Including Via Signaling Transfer Points. The Message Handling Functions Are Responsible For The Routing Of Message Through The Signaling Network To The Correct Exchange. Signaling Network Management Function Control The Configuration Of The Signaling Of These Functions Includes Network Reconfiguration In Response To Status Changes Of Network, E.G. If An Exchange Within A Signaling Network Fails, The Level 3 Of Same Rout Message And Avoid The Exchange That Has Being Failed.

The Level 1 & 3 Constitute A Transfer Mechanism That Is Responsible For Signal Transformation In Messages From One Signaling Point To Another. The Combination Of Both Of Signaling Point Is Known As Message Transfer Part (Mtp). Mtp Does Not Understand The System Of The Message Being Transferred, But It Controls A Number Of Signaling Network And Network Messages. This Means That Messages Are Delivered To Routed Exchange In Uncorrupted Form And In The Sequence That They Were Sent, Under The Failure Conditions In The Network.

Level 4-User Messages Part

It Comprises The User Parts ,User Is Not Confused With The Subscriber. User Part Of Level 4 Of The Layered Structure And Include Messages, Message Coding And Messages Necessary To Handle Basic Telephony And Isdn Services. A Key Feature Is That The Management User Parts May Be Standardized Mtp. Three User Parts Have Been In This, These Are Telephone User Part (Tup), The Isdn User Part And The Data User Part (Dup). These All Are Defined In The Form Of Message Procedure And Formats.

Application Of Level Structure

The Application Of The Level Structure Is Illustrated In The Previous Figure. Exchange A & B Are Directly Connected By Speech Circuits. A Signaling Link Is Also Available Between Exchange A & B. It Is Shown That Level 4 Is Closely Associated With The Control Function Of The Exchange.

If The Control Function Of Exchange A Needs To Communicate With Control Function Of Exchange (E.G. To Initiate The Setup Of A Speech Circuit Between The Exchanges), The Control Function Of Exchange A Request The Level 4 Functions To Formulate An Appropriate Message. Level 4 Than Request The Message Transfer Part (Level 1 To 3) To Transport The Message To Exchange B. Level 3 Analyses The Request And Determines The Means Of Routing The Message To Exchange B .The Message Is Then Transported Via Level 1 & 2.

Upon Receipt Of The Message By The Mtp Of Exchange B, Levels 1 & 2 Deliver The Message To Level 3. Level 3 At Exchange B Recognizes That The Message Has Arrived At The Correct Exchange An Passes Message To Level 4. Level 4 In Exchange B Than Interacts With The Control Function To Determine Appropriate Action And Response. If Problem Arises In The Transmission Process Between Exchanges A & B, Causing Message Corruption, The Level 2 Function Are Responsible For Detecting The Corruption And Retransmitting The Information. If The Signaling Link Between Exchange A & B Is Not Available (E.G. Failure Of The Link), The Level3 Functions Are Responsible For Rerouting The Information Through The Signaling Network To Exchange B.

Using These Techniques, Exchange A & B Can Send Each Other Appropriate Message Until The Need To Communicate On A Particular Transaction Ceases (Speech Circuit Between Exchanges Is Released).























Call Processing In Ocb283



























Ocb 283 Functional Diagram



Steps:
(I) When A Subscriber Goes Off Hook, It Is Detected By Line Equipment. The Change In Loop State Is Detected By Microprocessor During Its Cyclic Scanning. The Csnl Allots Free Ts On Lr For This Call. The Csnl Prepares A New Call Message And Sends It To Pu/Pe (In Sma) Over A Signaling Link Through Mcx. The Message Is Sent In Local Version Of Ccs#7.

(Ii) Pu/ Pe Receives This Message And Sends It To Mr Over Mas. It Indicates Ur No. Ut No. (Line Card No.), Equipment No. And Time Slot Allotted.

(Iii) Mr Allots A Free Register To Handle This Call. It Notes Down Ur Number, Ut Number, Equipment Number And T/S Allotted For The Subscriber. Now Mr Obtains Ur-Lr To Smx-Lrx Correspondence From Mq.

(Iv) Mr Obtains Class Of Service Data From Tr.

(V) Mr Orders Com To Connect Dial Tone To The Free T/S Allotted To Subscriber. If Subscriber Has Dtmf Instrument Orders For Connection For Rgf To The T/S Of Subscriber And Then Orders For Dial Tone Connection.

(Vi) Mr Also Sends Acknowledgment Message To Csn.

(Vii) On Receipt Of Dial Tone, The Subscriber Dials Called Party’S Number. The Ut (Terminal Unit I.E. Subscriber Line Card) Disconnects Dial Tone From The Calling Subscriber.

(Viii) Csn Sends These Digits To Pu/Pe Through The Same Path And Signaling System.

(Ix) Pu/Pe Sends These Digits To Mr Over Mas.

(X) On Receipt Ion Pf First Digit, Mr Orders Com To Disconnect Dial Tone. (Ut Has Already Disconnected The Dial Tone From Subscriber).

(Xi) On Receipt Of First Two Digits, Mr Calls Tr For Pre Analysis. Tr, After Analysis Of First Two Digits Tells Mr, The Type Of The Call I.E. Local, Std Etc.


(Xii) After Receipt Of Adequate Number Of Digits (Or All The Digits In Case Of Local Call) Mr Again Calls Tr For Analysis. Tr Supplies Called Party’S Address And Charging Information N To Mr.

(Xiii) Mr Carries Out Party’S Test To Whether It Is Free Or Not (Path Mr-Pu/Pe-Csn).

(Xiv) Csn Test The Called Party’S Equipment. If It Is Free, It Connects The Ringing Current To Called Subscriber. It Also Allots A Free T/S On Lr And Sends A Message To Mr Indicating Lr-T/S Of Called Subscriber.

(Xv) Mr Order Com For Connection Of Ring Back Tone To Calling Subscriber. It Also Obtains Ur-Lr To Smx Lrx Correspondence For Called Subscriber. Mr Waits For Called Subscriber Reply.

(Xvi) When Called Subscriber Replies, The Concerned Csn Sends A Message To Pu/Pe. Pu/Pe Sends The Message To Mr.

(Xvii) Mr Orders Com To Disconnect Ring Back Tone Mr Orders Mq For Connection Of Calling And Called Subscriber Time Slot. Mr Also Orders Tx For Charging The Calling Subscriber. As Per Data Supplied By Tr, Mq And Tx Give Compliance.

(Xviii) The Subscribers Are Now In Conversation Phase. Mr Hands Over The Surveillance Of Calling And Called Subscriber. To Respective Csn And Release.

(Xix) When Calling Subscriber Goes Off Hook, Csn Informs Pu/ Pe. Pu/Pe Informs Mr. Mr Releases The Connection. If Called Subscriber Goes Off Hook, Mr Sets A One-Minute Timer And Releases The Connection After The Expiry To Of This Time.



Hardware Configuration

Ocb 283 Exchange Comprises Following Hardware Units:

1. Subscriber Access Units (Csnl, Csnd, Csed).
2. Trunk And Junction Connection Units (Smt).
3. Switching Matrix (Smx).
4. Auxiliary Equipments (Sma).
5. Control Units (Smc).
6. Communication Multiplex.
7. Time Base Generator (Sts)
8. Operation And Maintenance Unit (Smm).

The Subscriber Connection Units Csn, Smts And Smas Are Connected To Switching Network Through Pcm Links. The Interchange Of Message Between Smt, Smx, Smas And Control Units Smcs Takes Place On ‘Mas’ Token Rings. The Control Unit Interchanges Messages With One Another And With Smm On ‘Mis’ Token Rings. The Smm Is The Operation And Maintenance Functional Unit And Is Duplicated As Smma And Smmb. These Are Work In Pilot/ Standby Mode.

The Smcs Are The Units, Which Hold Control Functions Mr, Tx, Tr, Mq, Pc, Gx. These Functional Units Are In Software Form And Are Duplicated Except Mr, Which Can Be More Than Two. The Duplicated Function Work In Load Sharing Mode (Except Pc Which Works In Pilot/ Standby Mode Hence Smc Can Be Minimum 2 And Maximum 32 As Per Design.

The Sma Station Holds The Eta And Pupe Functions And These Are Also Minimum 2 To Maximum 32. Smt Station Which Is The Interface For The External Pcms Is Made Of Duplicated Hardware And Can Handle Either 32 Pcms If Smt1G Or 128 Pcms If 2G. The Smt’S Hardware Is Fully Duplicated And Functions In P/R Mode.

Lr





Lr





Pcm Junction Mas





Mis



General Architecture Of Ocb 283


Description Of Hardware Units

1) Subscriber Access Units :

Subscriber Connection Units (Csn) Are So Designed That They Can Be Equipped With Either Analogue Subscriber Or Digital Subscriber. Or Both. The Cards For Analogue Subscriber And Digital Subscriber Are Different, But Can Be Equipped In Any Slot Of The Shelf. Csn Can Be Either Placed In The Exchange Switch Room Or At A Remote Location. Further Subscriber Card Shelf Known As Concentrator Can Also Be Placed At The Rack Or At The Remote Location. These Features Provide Great Flexibility To Meet Any Type Of Requirement Of Dense Or Sparse Connection Densities. Depending Upon Their Location, Csn Is Known As Csnl Or Csnd And The Subscriber Shelf Is Known As Local Or Remote Concentrator Cnl Or Cne.
The Csn Enables The Connection
- Of Analogue Subscriber Lines:
• Standard 2-Wire Lines
• Battery Reversal
• Remote Metering
• Telephone Booths

- Of Digital Subscriber Line Giving These Subscriber To The Numeris Network Services.
• Basic Rate (2B+D: 2 * 64 Kbps + 16 Kbps)
• Primary Rate (30B+D: 30 * 64 Kbps + 64 Kbps)
• For Low Rate Data Transfer, The Csn Offers The Frame Service Which Allows The Transport Of Message In The D-Channel
Depending Upon The Distance Separating The Csn From The Exchange To Which It Is Connected, The Link Between The Exchange And The Csn Are Direct Or Use Pcm Transmission Mode. The Direct Connection Requires Less Equipment Then The Pcm Transmission Mode. The Csnl Is Connected To Switching Matrix Through A Minimum Of 1 Glr Or A Maximum Of 2 Glrs. Group Of 8 Lr Is Called As A Glr And Each Lr Is A Pcm Link Having 32 Time Slots. The Csnd Is Connected To Smt Rack Through A Minimum Of 2 Pcm And A Maximum Of 16 Pcms.
The Message Interchange Between Csn And Control Units Takes Place On Common Channel Signaling Using Local Version Of Ccs37 Signaling. The Csn Is So Designed That It Can Be Connected To Any Switch Supporting Ccs#7 Signaling. This Csn Can Have One Basic Rack And Up To 3 Extension Racks. Its Architecture Can Be Broadly Divided Into Two Parts, These Are

(I) Digital Control Unit (Ucn).

(Ii) Concentrators (Cnl Or Cne).





(I) Digital Control Unit (Ucn)

The Digital Control Unit Is The Interface Between Concentrators And The Exchange. It Is In Basic Rack. The Basic Rack Is Placed In Switch Room For Csnl And At Remote Location For Csnd. It Can Be Further Broken Down Into Two Parts,

A) Control And Connection Units (Ucx)

There Are Two Such Units, Which Are The Controlling Logics Of The Csn. These Operate In The Pilot/ Standby Mode. The Active Ucx Controls The Working Of Csn And Also Updates Standby Ucx. In Case Of Any Faults In The Active Ucx, The Switch Over Takes Place Without Interruption To Existing Traffic. This Comprises A Processor Board Tpucd, A Coupler Board Tccsc And A Switching Matrix Tcrcx.

The Tpucd Board Performs The Control Unit And Memory Function For The Csn Logic. It Is ‘Master Station’ Comprising An I486Sx Microprocessor Clocked At 20 Mhz, An 8-Mb Ram Organized In 32-Bit Word. It Has Also Interchange Memory Function. This Is A ‘Slave Station That Comprise Mainly A 4-Mb Private Memory Organized In 16-Bit Word.

The Tccsc Board Supports Svc7 Coupler, It Provides Level 2 Of Signaling Protocol No.7 For 64 Kbits Channels. This Coupler Also Provides Level 2 Of The Uc-Ut Dialog Protocol. This Board Also Has Rxcn Coupler; It Is Used For Network Marker And Pcm Alarm Management. This Board Also Has Auxiliary Function, Used For The Generation Of The Idle Code On The Available Channels.

The Board Tcrcx Makes Up The Csnd Switching Matrix It Has An Internal Parallel To Serial Interfaced Designed To Control The Time Division Switching Matrix Gate Array. This Network Consists Of A Single Time Division Stage. It [Provides For The Sequencing Of The N * 64 Kbits Links. This Switching Matrix Has Different Interface On The Lri Side And Bipolar Interface On The Lre Side. It Also Has A Passive Control Of Connections. It Is Used For Generation Of Timing And Synchronization Signal. Required For The Operation.

The Board Tcsuc In Charge Of Coupling The Csn Control Logics. This Board Is Functionally Divided Into 3 Sub Units. First Sub Unit Processing The Switch Over Generated By A Fault, Second Sub Unit Processing The Gradual Switchover Requested By The Pilot Logic, The Third Subunit Processing The Resets Either Induced By Logic Faults Or Controlled Manually Or By A Super Watch Dog Device.

Auxiliary Equipment Processing Group (Gta)

This Auxiliary Processing Group Includes A Number Of Csn Auxiliary Functions Namely

• Generation Of Tones And Recorded Announcements For The Local Communication In Case Of Remote Connection To The Exchange. It Is The Role Of The Tfilm

• Recognizing The Two Frequency Signals Of The Pushbutton Subscribers Telephone Through Appropriate Receivers. In Case Of Ocmt, Supplementary Frequency Receivers Can Be Loaded With Digital Concentrators Because The Two Trf8 Planned For The Gta Can Be Insufficient To Process The Whole Pushbutton Analogue Traffic

• Csn Alarm Processing In The E Case Of Csn Connected In Remote Mode. This Operation Is Performed By Means Of The Tcpos.

• The Test Of Subscriber Line Connected To The Local Numeric Concentrators Through Tmln Associated To Its Commend.


Concentrators

The Shelf, Which Accommodates Subscriber Line Cards, Is Known As Concentrators. The Concentrator Can Either Be Co-Located With The Digital Control Unit In Which Case They Are Known As Local Concentrators Cnl Or At Remote Location In Which Case They Are Known As Remote Concentrators Cne. When A Remote Concentrator Is Used Then To Connect Exchange Pcm To Digital Control Unit An Interface Shelf Icne Is Required. The Maximum Capacity Of A Concentrator Is 256 Subscribers. When All The Concentrators Are Local A Maximum Of 19 Concentrators Can Be Equipped In One Csn Having 4 Racks, Where As If All Are Remote Or If At Least 2 Are Remote, A Maximum 20 Csn Can Be Equipped In One Csn. Depending Upon The Configuration Each Cnl Accommodate Following Type Tus.

• Individual Subscriber- Tabas, Tabazb, Tabasb
• Special Subscriber- Tabaf, Tabazf
• Dedicated Links Lf2-4 Wires: Tdqf
• Multi Way Junction Of 64 Kbps Tadl
• V5.1 Interface Tcv51
• Digital Subscriber With Basic Rate Access Tabn2G, Tabn3G
• 1 Reception Terminal Unit For The Digits Transmitted By The Push Button Subscriber Sets Trf8
• 2 Clock And Network Line Interface Tchlr, Tchle
• Digital Subscriber With Primary Rate Access Tadp, Tadpb, Tadpb2

Tabas, Tabazb: These Tus Comprised Of Subscriber Line Interface That Divide The Transmission And Reception Speech Channels And Power Up The Subscriber Line Through An Resistance Bridge Of 2* 200 Ohms For Tabas And 2 * 400 Ohms For Tabazb

Tabaf, Tabazf: These Uts Enables The Connection Of 16 Analog Subscriber Lines With The Remote Charging And Battery Reversal Functions. The Equalization Impedance, The Transmission And Reception Gains As Well As The Line Current Limitation Can Be Programmed For Each Subscriber Line Interface Circuit And Takes Four Values.

Tdqf: This Ut Is Supposed To Connect Up To 4 Dedicated Link Of Low Frequency To 2 To 4 Wire Wires Used To Apply Specific Application Such As High Quality Transmissions.

Tadl: This Ut Enables To Connect M/W Junction At 64 Kbps Used For Specific Application.

Tcv51: This Ut Enables The Connection Of An Access Network On To The Csn Through A V5.1 Interface. It Is Considered By Exchange As Ut With 32 Possible Equipments Units. It Only Enables The Support Of 30 Analogue Subscriber Or 15 Isdn Subscribers. The Allocation It Number To V5.1 Equipment Is Done Upon The Creation `Of A V5.1 Subscriber, An Analogue Subscriber Using An It And An Isdn Subscriber Using 2 It’S Of The V5.1 Pcm.

Tcpol: This Ut Takes Part In The Cnl Defense And Performs Under The Ucn Control. It Is Used For Blocking One Or More Uts By Blocking Wire, Which Entirely Isolates The Involved Ut On Transmission. This Prevents Any Disturbance On The Links By A Faulty Ut. Signaling Of The Timing Signal Distribution Faults Seen By The Interface Board Tchlx. It Also Isolates The Bus In Charge Of Switching To The Subscriber Line Test Circuits And Its Connection To The Cnl Internal Test Device Or External Test Device. Testing Of The Signaling Transmitted By The Subscribers Line Equipment.

Trf8: This Terminal Unit Analyzes The Frequencies Transmitted During Dialing From A Subscriber Push Button Set And Transforms Them Into A Message That Indicates The Number Dialed. It Comprises 8 Frequency Receivers, Allowing The Recognition Of The Numbers Corresponding To 8 Simultaneous Calls..








Connection Of Local And Remote Concentrators To Csnl

2) Trunk And Junction Connection Unit (Smt) :

Pcm Time Slot By Smt. The Sab Function (Branch Selection And Amplification) Is This Is Also Known As Pcm Trunk Control Station. This Smt Provides An Operational Interface Between The Pcms Coming From The Exchange (Csnd Or Csne) And The Switching Center. The Current Version Of Smt Being Supplied To Our Exchanges In India Is Smt2G. It Is New Functional Variant Of The Smt Station.

Smt2G Consists Of Duplicated Processing Subsystems. Smta And Smtb, Which Are Connected Through Internal, Links Lism. Both Of Them Are Connected To Pcm Interfaces As Well As To Mas Token Rings. Pcms Are Connected To Pcm Interfaces, Which Are Not Duplicated. Smt2G Is Connected To Smxa And Smxb Through 128 Pcms, Which Are Connected To Sab Branch A, And Sab Branch B. Speech Samples Are Sent On Both The Branches From Smx, But One Which Is Better Is Selected And Connected To The Concerned Also Not Duplicated. Out Of The Two Processing Logics, Smt A And Smt B, One Remains Active And Other Standby. In Case Of Fault In Active Logic, Automatic Switchover Takes Place Providing An Uninterrupted Service. Also Locovar Is Activated On The Faulty Logic And The Diagnostic Is Displayed On The Terminal For The Information Of The Maintenance Staff.

The Software Mlurm Is Loaded In The Smt To Perform Functions Of A Pcm Controller.

The Functions Performed On Receive Side-
• Convert Hdb3 Code To Binary.
• Extract Channel Associated Signaling.
• Manages Ccs#7 Messages Carried On Ts 16.
• Cross-Connects A Channel On Pcm To Ts On Lr.

The Functions Performed On Transmit Side-
• Convert Binary Code To Hdb3 Line Code.
• Inject Channel Associated Signaling
• Manages Ccs#7 Messages On Ts 16.
• Cross-Connects A Ts On Lr To A Channel On Pcm.
The Organization Of Each Smt Is Based On The Bsm And Includes
O A Main Multiplex Line Driver (Cmp).
O An Optional Pup Function.
O A Common Memory Function.
O One Or Two Sm Exchange Termination Interface Controller



Lae/Las 128
Lrs


Lism

128
Lrs
Mas Mas
A B
Lae/Las
64 Pcm General Architecture Of Smt 2G
The Functions Are Implemented On The Following Boards

O Cmp: Acaja And Acajb Boards
O Pup: Acutg Board
O Mc: Acmgs Board
O Ctlh: Ictsm Board

The Control System Comprises Two Processing Subsystem Or Individual Sm Station Having A Direct Inter Sm Interface Enabling Them To Communicate. This Architecture Is Dictated By The Operating Mode To Guarantee Dependability, A Duplicated Sm System Is Needed. The Concept Of Active Sm Is Retained In The Etp Initialization Process, Where Only The Active Sme Is Recognized. A Hardwired Device Divided Between The Two Smes And Physically Implemented On The First Ictsm Board Of Smes Handles Control And Positioning Of The Prs Signal.
Knowledge Of The Active Smes Is Sent To The Outside Environment Via A Hardwired Signal Prs. The Signal Is Needed Among Other Things By The Etp To Know Which Processing Subsystem Is Active During The Initialization Phase.

The Cmp Comprise Two Boards For Connecting The Station To A Multiplex (Duplicated Ring), A Master Board Acaja Based On 68020 Microprocessor. This Board Supports Ring A Of The Multiplex And Provides The Processing Power. It Is Connected To The Bsm. A Slave Board Acajb Controlled By The Acaja Board Processor Supports Ring B Of The Multiplex And Is Not Connected To The Bsm.

Acmgs, This Is A New Generation Common Memory With A Capacity Of 16 Mbytes Protected By A Self-Correcting Code For Each 32-Bit Word. The Slave Board Never Attempt-Pts To Seize The Bus But Is Accessible To All Master Boards Through Its Memory Plane And Its Interface Area. When Used With An Acutg Cpu Board, It Offers This Board A Direct Interface Via A Local Bus. The Function Of This Board In The Unit Is To Enable The Various Master Processors To Communicate In Message Mode Via Queues And Also Provide A Protected Information Storage Area For Permanent And Semi Permanent Programs And Data.

The Ictsm Board Is Organized Around A Common Acutg Section (68030, Partly Protected 4 Mbytes Dram Standard Private Peripheral Devices And Bsm Interface). The Sme Switchover Management Devices Supplement This Basic Function. Inter Smes Dialogue. The Ictsm Board Number (I) Is Linked To Its Counterpart In The Other Smes Via A Programmable Bit Rate Hdlc Link, Lism That Is Designed To Facilitate Interchanges Between Equivalent Boards.

3) Switching Matrix (Smx) :

The Smx Station Is An Element Of The Central Connection Matrix Of The Ocb283 System. Under The Control Of The Control Stations, It Performs The Following Functions.
• Clock Reception And Distribution
• Control Of The Station
• Interface With The Connection Units And The Other Smx Stations
• Connection Of Cx Input Lines To 256 Cx Output Lines.
• Connection Security.
• Help In Fault Location Of The Locovar
• Station Alarm Processing.

The Switching Network In Ocb283 Is Single ‘T’ Stage System. It Is Made Up Of
A) Host Switching Matrix
B) Branch Selection And Amplification

A) Host Switching Matrix

The Host-Switching Matrix Consists Of Two Identical Branches A And B. The Host-Switching Matrix Is Implemented On The Hardware Units Known Matrix Control Station (Smx). Each Host Switching Can Host Up To 2048 Incoming Pcm Links (Lre) And 256 Outgoing Pcm Links (Lrs). Out Of 2048 Incoming Links, Only 256 Links Are Directly Coming Fro This Matrix Control Station. The Remaining Links Are Coming Fro Other Seven Smxs. In Full Configuration, The Host-Switching Matrix Is 2048 * 2048 Matrix. This Is Shown In Below Figure.

A Matrix Control Station Can Establish Connection Between Ant Ts On2048 Lre And Any Ts On 256 Lrs. Similarly A Host-Switching Matrix Can Establish Connection Between Any Ts On 2048 Lre And Any Ts On 2048 Lrs. Three Standard Configurations With 256 Lrs, 1024 Lrs And 2048 Lrs Are Available. The Matrix Control Station Is Built Around A Processor, Which Implements Software Machine Malcom Functions, To Establish And Break Connection Between Time Slots. It Also Carries Out Two-Way Communication With Other Units In The System Over Mas Rings.

0 To 256 Lre
0 To 255 Lrs



256 To 511 Lre 256 To 512 Lrs




1792 To 2047 Lrs







The Time Switch Comprises Of A Speech Buffer Memory, A Control Memory, An Incoming Highway Of Digital Speech In Parallel Bits And An Outgoing Highway As Shown In The Diagram. This Is A Input Associated Time Control Switch. In This Switch The Buffer Memory And The Control Memory Are Controlled Write Type I.E. The Writing In Its Control. The Control Function Writes In The Control Memory At The Location Corresponding To The Incoming Time Slot Number The Location Where Ir Should Be Written In The Buffer Memory. Both These Memories Are Sequential Read Type. Reading Of Control Memory Gives The Address In Buffer Memory For Writing The Incoming Byte. Thus Reading Of Buffer Memory Sequentially The Ts Will Be Read Fro The Location Given By The Control Memory. Thus A One-Way Time Switching Has Taken Place. Similarly A Both Way Switching Requires Two Sets Of Such Switches.

The Switching Is Done In Ocb283 In Two Fully Duplicated Branches Simultaneously. For This Purpose For Each Connection Units The Lr Links Originates In To Parallel Branches Toward Two Parallel Sets Of Switching Matrices Called Smxa And Smxb. The Branch Of Such Networks Are Called A And B Branches. Also The Received Side Lr Links Come From Both The Smxs A & B And Are Terminated On The Respected Connection Units. Referred To As Ur In Figure Below. The Duplicated Branches Of Switching Have Been Designed To Provide High Reliability Switching Path For Such Diverse Purpose As Data Switching, Video Conference, And Isdn Applications Etc. With The Duplicated Path Of Switching If There Is Error In One Path The Other Path That Is Good Can Be Used Continuously Without Interrupting The Call In Progress.

B) Sab Function :

The Connection Unit Has Their Internal Duplicated Hardware, Which Is Called Control Logic, Which Works In Pilot/ Reserve Arrangements. Also They Have Non-Duplicated Hardware Such As Subscriber’S Cards And Pcm Termination Cards. The Duplicated Lrs Originate From Function In Connection Units Called Sab (Selection And Amplification Of Branch). Its Role Is To Generate Two Sets Of Lrs In Trans Direction With Calculation Of Parity Etc. And Compares To Detect Any Error In The Two Branches. In Case Of Error The Sample From Only The Good Branch Are Taken After Automatic Testing Of The Transmission Of Both The Branches By The Common Control And The Faulty Branch Is Withdrawn From The Service. The Connection Unit Lr Links Are Formed Into Group Of 80Lrs At The Factory Into Cables With Both Ends Terminated With Plugs For The Convenience Of Installation. Such Group Of Lrs Is Called Glr. The Figure Shows How The Glrs Are Terminated At The Two Branches Of Smx In Ocb 283.


4) Auxiliary Equipment Control Station (Sma)

The Sma Station Receives The Auxiliaries From The Ocb283 Exchange. These Are
• Frequency Receive/ Generator Used For Setting Up Calls
• Conference Circuits.
• Tone Generator, Time Management Operator
• Ccitt Number 7 Signaling Receiver/ Transmitters.

This Sma Is Linked To The Switching Matrix By A Set Of 8 Lrs (O/G Matrix Links) Carrying The Signals Generated Or To Be Analyzed, Through The Switching Matrix The Sma Receives The Basic Timing Fro The Exchange. To The Mas Series Communication Support Facility, It Ensures Information Transfer Between The Sma And The Ocb283 Command Units. To The Alarm Multiplex. The Sma Contains The Following Two Functional Units
(I) Eta
(Ii) Pupe

Eta Contains The Following Subscriber Components:
• Frequency Receiver/ Generators
• Conference Call Circuits
• Tone Generators

The Frequency R4Eceivers/ Generator Recognize The Digits Dialed Through Dtmf Instrument And Also The Mf (R2) Signals Received On Junctions. They Also Generate The Various Frequencies Required For Mf Signaling And Testing Etc.
The Conference Circuits Are Used To Setup Connection Between A Maximum Of 4 Subscribers. These 4 Subscribers Can Hold Conference On The Telephone I.E. They Can Talk To Each Other.
Tone Generator Generates The Various Tones Required To Be Connected During Call Processing. These Tones Are Dial Tone, Busy Tone, Ring Back Tone, Processing Tone Etc.
Pupe Performs The Level 2 And Part Of Level 3 Functions For Ccitt No. 7 Signaling. The Rest Of The Level 3 Functions Performed By Pc. The Various Functions Performed By Pupe Are As Below

Transmit Side
• It Sends ‘Flag’ And ‘Check Bit’ In The Hdlc Frame While Transmitting Ccs#7 Messages. It Also Inserts Zeros, When There Are More Then 5 Consecutive Ones In The Message.
• Pupe Send Filling Signal Units (Fisu) Automatically When There Are No Messages To Be Sent.
• Pupe Also Sends Link Status Signal Unit (Lisu) When Commanded.
• It Retransmits A Signal Unit On Receipt Of Negative Acknowledgement.

Receive Side
• On The Receipt Of Ccs#7 Signaling Messages, It Eliminates Zeroes Which Were Inserted After Five Consecutive Ones.
• It Detects The Flag And Also Computes The Checksum And Compares Them With Check Bits. If These Two Matches, It Sends Positive Acknowledgement Otherwise It Sends A Negative Acknowledgment.
• It Eliminates Fill In Signal Units, As They Do Not Carry Any Information.

Either Eta Or Pupe Or Both Can Be Implemented On The Same Sma. When Both Are Implemented On The Same Sma, Mlpupe (Logic Machine Pupe I.E. Pupe Software) Is Loaded On The Principal Processor (Pup) And Mleta Is Loaded On Secondary Processor (Pus)
When Only Pupe Is Implemented On Sma, It Is Loaded On Pup And When Only Eta Is Implemented, It Is Loaded On Pus. Only First Two Etas Have Tone Generators Ccfs And Rgfs Are Provided As Per Requirements. The Pcb Used Is Common For Rgf; Ccf And Tone Generators. Only The Software Is Different. When No Ccf Or Tone Generator Is Required An Eta Can Have Maximum Of 96 Rgfs. An Sma Is Connected To Smx By 8 Lr Links. The Following Table Illustrates The Capacity And Modularity Of Sma.

Sma Units Equipped With Capacity Max & Min.
Eta Alone 96 Rgf 2 To 32
Pupe Alone 64 Ccs#7 Channels 2 To 15
Eta And Pupe Both 64 Rgfs/ 32Cccs#7 Channels 2 To 15
The Sma Is Organized Around A 16 Bit Standardized Bsm Bus. Sixteen Boards Can Be Connected To The Bsm:

1. An Acaja Board Intended With The Assistance Of The Acajb Board To Mange Transfer Via The Mas Call Multiplex.

2. An Acmcq Board Supporting The Mass Memory Of The Station.

3. An Acutr Board, Which Provides Backup Processing Power.

4. A Maximum Of 12 Board S Carrying Out Specific Operations Devolved To The Sma.

5. A Pair Of Icid Board Which Provides Link Between The Branches Of The Connection Matrix And The Sma.

6. And Acala Board For The Collection And Transmission Of Alarm Read In The Sma.

Ictsh Functions The Simultaneous Call Function. Simultaneous Call Involving Up To A Maximum Of 4 Subscribers Is Possible. This Function Enables Add-On Conferencing With The Possibility Of Discreet Listen, Indicating A Call In Hold, Making Operator Calls. The Tone Generator Function Generates Voice Frequency Signal These Signals Are Single, Two, Three Or Four Frequency Sequence Includes A Maximum Of Eight Send Pause Sequences. An Ictsh Board Generates 32-Voice Frequency Signal. Frequency Composition And Sequencing Are Transmitted On Sma Initialization And Remains Through Out Operating Phases. The Rgf Terminal Analyzes And Sends Voice Frequency Signals; These Signals Are In General Single Or Two Frequencies And Attached To A Signaling Code. An Rgf Terminal Is Dynamically Placed By Control Units Within A Signaling Code It Detects The Presence Of Receive/ Incoming Signals And Transmit Their Frequency Composition To The Control Stations. It Always Transmits As A Response To Mono Or Bi-Frequency Pulse Control Instruction. Eight Rgf Terminals Can Be Implemented On Ictsh.

Achil Functions On 16 Channels It Carries Out Level 2 Hdlc Type Signaling Processing And Has Two Servers, Which At The Frame Level Has The Following Role
Hdlc Direction, On Send (Sending Of Flag Crc Calculation ‘0’ Insertion) And On Receive (Elimination Of Inserted ‘0’S Flag Termination Crc Verification). Ccitt#7 Directions On Send (Automatic Send Of Filler Frames, Repetition On Command Of Status Frames) And On Receive (Automatic Elimination Of Filler Frames Not Carrying Useful Information).

Ichor Board Maintains Time For The Ocb 283 Exchange. Time Information Is Doubly Useful In Switching. It Enables Determination And Labeling. It Must Be Protected Against Slow Drift, Which Implies The Need For Repeated Time Resetting And Protection Against Sudden Loss Caused By Hardware Faults Normally.

Acaja And Acajb Board Is A Coupler Connecting The Sma To Mas Multiplex And Enabling The Dialog With The Control Units. The Information Exchanged Is Channel Associated Signaling From The Ictsh Board. These Are Signals Sent By The Rf Of The Rgf Station Signals Detected In Voice Frequencies. Messages From And To Applications Implemented By Sma Processor.

Acala Board Collects Alarm And Is Self Powered. In Sma The Alarm Sending Entities Are The Two Converters Of 48 Volts.

Icid Board (Differential Interface Board) Provides For The Security Of The Matrix- Ur Link In The Ocb 283. It Supports The Following Functions

• Reception Of 8 Lrs And Of Associated Time Base From Rcid Board Of One Branch Of The Mcx.

• Sending Of 8 Las And 4 Associated Time Base To The Urs (Sma, Smt)

• Mutual Help By Reception Of 8 Lrs Fro The Other Branch Of The Mcx With The Associated Dts.

• Selection Of Time Base.

• Processing Of Extra Bits Transmitting On The Lrs.

• Generation Of Availability Signals Accompanying Lass.

• Processing Of Lae Links Sent By Urs And Generation Of Lre. (I/C Matrix Link).

• Synchronization Of Lrs From The Mcx And The Mutual Help Of Lrs.

5) Control Units (Smc):

Since All The Control Units Like Mr, Mq, Tx, Tr Etc. And Sma Are Implemented On A Common Type Of Hardware Architecture Known As Station. It Is Worthwhile To Understand The Architecture And Concept Of Station. A Station Is Built Around A Multiprocessor Station Bus Bsm. One Or More Processor And One Or More Intelligent Couplers Connected To This Bus. They Interchange Data Through The Common Memory. The Principal Or Main Processor Is Connected To Common Memory Through A 32 Bit Private Bus Apart From Through Bsm. All The Processor Are Motorola 68020 Microprocessor And Operates At 15.6 Mhz Clock. Multiprocessor Station Bus Bsm Is 16-Bit Bus, Which Operates At 44.8 Mbs.
A Block Schematic Of The Station Is Shown In The Figure Below.

















Smc Station Configuration

There Can Be One Principal Processor (Pup) And 4 Secondary Processors (Pus) In A Station. Similarly There Can Be One Main Coupler (Cmp) And Up To 4 Secondary Coupler (Cms). Specific Coupler Can Be Equipped For Specific Purposes. A Station Can Function As Mr, Tr Or Any Other Unit When Particular Software Is Loaded In The Station. Depending On Traffic And Processing Requirements, Software Of Either One Or Functional Units Can Be Loaded In The Same Station. Also Depending On The Above Requirements, A Functional Unit Can Be Implemented On Principal Or Secondary Processor And On Main Or Secondary Coupler.

To Permit Co-Habitation Of Many Software Machines Ion The Same Station, Basic Software Is Known As Hyper Visor Is Provide On The Station. Another Software Known As Supervisor Provides Communication And Loading Facilities. The Station Is Generally Known As Smc.

There Are 6 Common Control Function In A Ocb283.The Following List Illustrates Their Minimum And Maximum Numbers.


S. No. Name Of Unit Minimum Maximum
1 Mr 2 7
2 Tr 2 2
3 Tx 2 2
4 Mq 2 2
5 Pc 2 2
6 Gx 2 2


They Are Known As Logical Machines In Software Form. These Logical Machines ‘Ml’ Are Implemented On The Hardware Of Smc By Loading Suitable Software On It. An Smc Can Support Any One Or Many Mls Or Functions In Defined Combination. Accordingly Depending Upon Exchange Configuration And Traffic Requirement There Can Be Minimum Two Smcs Required And Maximum Number Of Smcs Can Be Minimum 32 But No More Than 15 Are Needed. The Planners And Manufactured Upio N The Traffic Data Decide The Required Number Of Smcs. In Addition To This Provision Of One Backup Smc Station. This Backup Station Is Not Loaded With Any Software.

Whenever, Any Smc Becomes Faulty It Sends Message To Smm. The Smm Blocks This Unit And Inform All Control Units Regarding Non-Availability Of This Unit. Smm Then Loads The Software Of All The Functional Units On The Backup Station And Brings It Into Service. Thus, There Is Automatic Recovery. Smm Also Runs Diagnostic Program On The Faulty Station And Prints Diagnostics On The Terminal.

Functions Of Various Common Control Software Mls. :


(A) Multiregister (Mlmr)
The Mr Establishes And Releases The Calls It Takes Real Time Decision Or Processing Of A Call. The Mr Also Consults Tr To Find Out Subscribers Entitlements And Stores Digits Dialed By Subscriber. It Also Orders For Connection And Is Connection Of Various Tones And Subscribers. In Addition To Call Processing Functions, Mr Also Carries Out Testing Of Circuits And Observation Function.

(B) Translator (Mltr)
The Tr Stores Exchange Database In Its Memory. On Request It Tells Mr The Characteristics And Entitlement Of Subscriber And Circuits. The Tr Also Stores The Routing And Analysis Data. It Converts Or Translates The Received Digit Into Equipment Number Of The Called Subscriber.

(C) Marker (Mlmq)
The Marker Carries Out Message Between Common Control Functions Mls And Connection Units For Subscribers Or Circuits. It Also Acts As ‘Gate’ For Message Which Pas From One Communication Domain Top Another. The Mq Also Supervises Semi Permanent Connection In The Network.

(D) Charging Unit (Mltx)
As The Name Suggests The Tx Carries Out Charging For Each Communication Set Up. It Also Keeps Charge Account Of All Subscribers. The Tx Also Prepares And Sends Detail-Billing Message To Smm. In Addition It Also Carries Out Subscriber And Circuit Observation Functions.

(E) Matrix System Handler (Mlgx)
The Gx Monitors The Connection In The Switching Network And In Case Of Fault, Carries Out Appropriate Defense Functions. It Also Periodically Or On Request Monitors Internal Links In The Switching Network.

(F) Ccs#7 Controller (Mlpc)
The Pc Carries Out Routing And Traffic Management Functions, Part Of Level 3 Functions For Ccitt No. 7 Signaling. It Also Carries Out The Defense Of Pupe, I.E. If A Pupe Develops Faults, It Is Automatically Blocked, The Semi Permanent Link Is Reconfigured And The Standby Pupe Is Brought In Service. The Pc Also Carries Out Observation Functions.


6) Communication Multiplexes (Mis, Mas And Mal) Token Rings:

In Ocb 283 Exchange The Communication Multiplex Highway Are Utilized For Interchange Of Messages Between Various Equipments Of Exchange. These Communication Multiplex Works On The Principal Of Computer Circular Lan Ring Using Token Ring Protocol. There Are Three Types Of Communication Multiplexed Highway According To Their Use.

1. Mis Interstation Multiplex

2. Mas Station Access Multiplex

3. Mal Alarm Multiplex.

The Mis Token Ring Is Providing For Interchange Of Message Between Two Smcs And Between An Smc And Smm.

The Mas Are Provided For Interchange Of Message Between Csnl, Smt, Sma And Smx On One-Hand And Control Units (Smc) On The Other Hand. A Maximum Of Four Mas Token Rings Is Provided In Compact Configuration

Mas Token Ring Can Be Minimum Nil And Maximum Four Duplicated As A & B.Mal Token Ring Is Provided To Handle Exchange Alarms From All The Hardware Stations Of Exchange Except Csnl.The Token Ring Confirm To Ieee 802.5 Standard And Operates At 4 Mbps. An Empty Token Circulates On The Ring When There Is No Message To Be Sent. A Token Contains Starting Flag, Access Control Byte And End Flag Of One Byte Each As Shown Below In Table.

Whenever A Station Wants To Send A Message It Checks The Status Of T Bit. If Tbit Is Zero The Token Is Free, So The Station Inserts Its Message In The Token And Sets T=1, The Station Books The Token To The Next Message. However If The Token Is Busy Which Is Indicated By T=1 The Books The Token By Writing Its Priority In Reservation Field. Whenever A Station Receives The Token, It Compares Its Own Address With The Destination Address Written In The Token. If The Address Matches The Station Receives This Message And Sends Acknowledgement. On Receipt Of Acknowledgement, The Transmitting Station Clears The Token And Sets The T Bit To Zero. If A Station Has Booked A Token, It Can Send The Message Only After It Has Been Released By The Transmitting Station

7) Time Base Generator (Sts):

Time Base Is Required To Synchronize Pcm Links Connected To Connection Units Like Csnl, Smt, And Sma Etc. The Time Base Is Generated Time Base Synchronization And Time Base Station (Sts) And Distributed To The Two Branches Of The Switching Network. These Branches Then Redistributed The Time Base To Above Mentioned Connection Units Along With Lrs. Sts Has Three Oscillators All Generating 8 Mhz And Sbt Time Base. The Switching Network Selects The Time Base As Per Majority Logic. So Even If One Of The Oscillators Is Out Of The Order, The System Is Not Affected. Sts Receives Sbt And 8Mhz But Supplies Sbt And 4 Mhz To Connection Units. There Is A Facility To Synchronize These Oscillators With An External Source By Equipping External Synchronization Network. This Facility Is Useful When The Exchange Has To Be Synchronized With The Network.

Empty Token:



8 Bit 8 Bit 8 Bit
End Flag Access Control Ac Start Flag

P P P T M R R R


Token With Message:


Sd Ac Fc Da Sa Info Fcs Ed Fs Fl












Token
Ring








(8) Operation & Maintenance Unit (Smm):

Smm Station In Ocb 283 Performs The Operation And Maintenance Functions. The Smm Station Has Full Duplicated Hardware Smma And Smmb. One Of The Two Smm Is Pilot And The Other Work As Hot Stand-By. For Both Smm There Are Two Mirror Images Hard Disks Of 1200 Mb Capacity. Pilot Smm Is Able To Access Either Of Disks. There Are Termination Of Peripherals Tty, Vdu For Operation And Maintenance. Smm Dialogues With All Smcs Over Mis Token Ring. Adjacent To Smm Rack There Is One Magtape Drive Unit Dbm. There Is One Streamer For Cartridge Drive In Smm Rack. There Are Up To 4 Alarm Reception Rings For Handling Exchange Alarms. Smm Receives All Alarms From Whole Exchange On Alarm Rings Mal. Smm Station Occupies Three Shelves Of A Ca Rack. Smm Rack Also Has Digital Voice Announcement System Mpna In Fourth Shelf.

The Smm Station Supports The Local Operational Maintenance Unit Om Handling Ocb 283 Supervision And Management Function. This Smm Is Provided To Supervise The Functioning Of Various Exchange Equipment And To Take Suitable Action In Case Of Malfunctioning Of Any Equipment. As Stated Earlier It Does The Defense Of Control Units In Case Of Faults. All The Files And Data Are Stored In Smm Hard Disk, Which Can Be Loaded In Any Unit. Smm Also Carries Out The Re-Initialization Of The Exchange When Required. The Smm Process Man Machines Commands And Execute Them. Smm Also Collects The Alarms From Various Units And Process Them. Smm Stores Detailed Billing Data In The Disk, Which Can Be Periodically Transferred To Magtape For Processing. Smm Runs Diagnostic Programs (Locovar) On The Faulty Units And Indicates The Faulty Pcb. In Nutshell, The Smm Executes All The Functions Related To Operation And Maintenance Of Ocb 283 Exchange.

The Smm (Maintenance Multiprocessor Station) Is Built Around Two Identical Microprocessors 68030. This Multiprocessor Station Work In Pilot And Hot Standby Mode. Each Of The Processor Has 4 Mbytes Private Memory And 16 M Byte Primary Memory. All The Components Viz. Processor, Memory And Coupler Are Connected On The Xbus. The Secondary Memory Devices Like Disc, Magtape Devices, Streamers Etc. Are Connected On The Scsi Buses, Which Are Connected To Xbus Through Couplers. The Two Smms Are Connected Through Hdlc For Exchange Of Switch Over And Other Messages. The Smm Are Connected To Mis Token Ring Through Couplers For Interchange Of Message With Control Units. Various Terminals For Man Machine Communication And Alarm Couplers Are Connected To Xbus Through Communication Coupler.
Each Disk Has A Capacity Of 1.2 Giga Bytes And Both Of Them Are Connected To Active Smm. In The Normal Operation Data Is Read From And Written Into Both The Disks Simultaneously. But Whenever One Of Them Goes Faulty The Other Disk Is Available For Read And Writ Operation. The Contents Of One Disk Can Be Updated From Other By Command. Streamer Has A Capacity Of 525 Mbytes. It Is Used To Load System Data Into Disks And For Taking Backup Of The Disks. Two Magtape Drives Are Provided. Charge Account Data And Detailed Bill Data Re Transferred From Disk To Magtape For Further Processing In The Billing Center. Digital Recorded Announcement Card Is Also Equipped In The Smm Shelf. The Announcements Are Connected To Up To 2 Pcm Of First Smt From Where They Are Connected To Subscriber Or Circuit As Per Requirements. One Smm (Pilot And Standby) Is Provided At Each Ocb 283 Exchange. However The Smm Can Be Connected To Network Management Center (Nmc) For Remote Management.

Each Processing Unit Is An Sm Station On The Multiplex Mis And Is Built Around The Xbus. It Comprises The Following Boards.

O A Processor Board Acytg And A Memory Board Acmgs (Linked By A 32 Bit Address Bit Local Bus)

O A Pair Of Boards Acaja, Acajb Providing The Interface To The Mis Multiplex.

O An Acftd Line Coupler Board For Managing The Terminal Bus Interface

O Two Acbsg Boards For Managing The Interface With The Two Scsi Buses.

O A System Board Accsg.

O The Line Coupler Have Only One Active Port To A Processing Unit At A Given Time And Are Used To Manage The Synchronous/ Asynchronous Links At Rates Up To 19200 Bauds (Actuj Board), Synchronous Or High Speed Links (Acj64) And The Alarm Multiplexes (Acral2 Board)

(A) Acutg/ Acmgs Board

This Board Supports The Rtos Operating System And The Application Software Running In The Smm. This Board Is Called The Primary Processor And Is Denoted As Such In The Initialization Phase. It Is Built Around 68030 Processor Running At 16.7 Mhz With A 4M Of Private Dram And Local Bus Interface Representing An Addressing Capacity Of 4 Gbytes. Acmgs Board Is A 16 M Memory Board That Can Be Addressed On $ Gbytes By The Xbus Or The Local Bus.

(B) Accsg Board

This Board Restarts A Processing Unit That Has Been Reset To Zero Via The Accsg Front Panel V2 Switch Or Following An Xbus System Switchover. This Board Acts As The Locovar Controller For The Xbus Agent, Positioning Messages Via The Intersystem Board Link From The Active Side. This Board Is Built Around The Common Core System The Parts Specific Is Consists Of Circuits Managing The 1 Mbits/S Inter System Board Link And Managing The Distributed Switchover Functions.

(C) Acftd Board

This Board Supports The Input/ Output Processor Iop. Its Operating System Is Syspes. It Enables Handler Software To Perform Terminal Bus Line Management Functions. There Is A Handler For Each Protocol Implemented At Line Level. The Parts Specific To It Form The Terminal Bus Interface Built Around The Acbt Gate Array Circuit.

(D) Acbsg Board

This Board Includes Complete Scsi Bus Input/ Output Software Stored In Ram. There Is Also Prom Resident Software Controlling Scsi Access, Used When Initializing A Processing Unit. Each Acbsg Board Supports The Two Separate Scsi Buses. It Is Built Around A 68030 Processor Running At 16.7 Mhz, With 512 K Of Private Sram. And Two Scsi Bus Interfaces Based On 53C90A Circuits.

(E) Acaja/ Acajb Board

These Boards Handle The Mis Function. The Smm Incorporates A Secondary Line Coupler Cms. As Well As The Token Ring Management Function. It Supports The Mlsm And Mloc Software Modules.

(F) Acj64 Board

This Board Is Used For Synchronous Line Coupler Providing The Interface Between The Smm And The Telecommunication Maintenance Networks. 64 Kbits Digital Link Can Be Used In Which Case The Line Coupler Is Supported By This Board Handling Up To Four Links. A Secondary Acj64 Board Can Provide A Link Duplication Option Or Increase The Number Of Links, There Are Four Boards And 32 Asynchronous Links. This Board Is Built Around The 2652 Hdlc Controller.

(G) Acala Board

This Board Marshall Alarm From The Ae5V40 And Ae12V Converter Of Their Respective Sub Racks. A Third Acala Board Marshall Alarm For Announcement Machine/Streamer.

(H) Digital Announcement Machine Mpna

Automatic Announcements Are Provided In Ocb 283 At The Switching Matrix In The Form Of A Pcm Coming From A Mpna, Which Has Digital Recorded Voice Messages Stored In Pcbs. There Are Two Pcbs Icmpn2 (Ram, Volatile Memory Gives Pcm) And Icsmp (Eprom, Saves Voice Announcement Digital). These Are Two Cards And Are Suited In Smm Racks And The Announcement Are Carried By One Pcm Link From Icmpn 2 And Are Connected To One Smt; From Smt The Lrs Go To Smx. At Smx Its Time Slots Are Used For Getting The Respective Announcements. The Mpna Is Controlled By Small Hand Held Control Device Called Micro Terminal For Storing And Modifying Of Announcement Using Microphone/ Earphone.



















Bibliography


I. Ocb 283 Service Manuals - Call Processing In Ocb 283

Ii. Www.En.Wikipedia.Org/Wiki - Common Channel Signaling No. 7

Iii. Ccs#7 Manuals - Principle & Requirements Of Ccs

Iv. Www.Tnd.Bsnl.Co.In - Features & Facilities Of The Ccs System

V. Ocb System Manuals - Hardware Configuration Of Ocb 283



I. Ocb 283 Service Manuals - Call Processing In Ocb 283

Ii. Www.En.Wikipedia.Org/Wiki - Common Channel Signaling No. 7

Iii. Ccs#7 Manuals - Principle & Requirements Of Ccs

Iv. Www.Tnd.Bsnl.Co.In - Features & Facilities Of The Ccs System

V. Ocb System Manuals - Hardware Configuration Of Ocb 283



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