Sumit's BSNL Training Report

SPN – EL2007461/10Branch - Electronics

BSNL TRAINING REPORT

BSNL, SDOP I, NAYAPURA, KOTA

2009

Sumit KumarSPN - EL2007461/10

Govt. Polytechnic College, Kota (Raj.)

PREFACE

Practical training in an industry is an essential part of an engineering curriculum towards making a successful engineer, as in an industry only a student can realize the theory thought in classroom and it also gives an exposure to modern technology.

In the field of Electronics Computer engineering there has been rapid development to

support the ever increasing volume information, so Electronics students has an opportunity

during Training period to knowledge about the latest technologies.

The training period of 28 days is not much sufficient to take complete knowledge of

technology used but one is expected to identify components, the process flow in an industry for

high efficiency and about the knowledge of product technology.

Practical knowledge means the visualization of the knowledge, which we read in books. For this we perform experiments and get observations. Practical knowledge is very important in every field. One must be familiar with the problems related to that field so that we may solve them and became successful person.

After achieving the proper goal of life an Engineer has to enter in professional life. According to this life he has to serve an industry, may be public or private sector or self-own. For the efficient work in the field he must be well aware of practical knowledge as well as theoretical knowledge.

To be a good Engineer, one must be aware of the industrial environment & must know about management, working in industry, labor problems etc., so we can tackle them successfully.

Due to all the above reasons & to bridge the gap between theory and practical, our engineering

curriculum provides a practical training course of 28 days. During this period a student in

industry and gets all type of experience and knowledge about the working and maintenance of

various types of machinery.

Since time immemorial, a man has tried hard to bring the world as close to himself as

possible. His thirst for information is hard to quench so he has continuously tried to develop

new technologies, which have helped to reach the objective.

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The world we see today is a result of the continuous research in the field of

communication, which started with the invention of telephone by Graham Bell to the current

avatar as we see in the form INTERNET and mobile phones. All these technologies have come to

existence because man continued its endeavor towards the objective.

This project report of mine, STUDY OF TRENDS TECHNOLOGIES IN COMMUNICATION

AND NETWORKING has been a small effort in reviewing the trends technologies prevailing. For

this purpose, no organization other than BAHRAT SANCHAR NIGAM LIMITED could have been a

better choice.

I have undergone by 28 days of training (after II yr.) at BAHRAT SANCHAR NIGAM

LIMITED, NAYAPURA, KOTA (Raj.). This report has been prepared on the basis of the

knowledge which I acquired during my 28 days (15-06-2005 to 13-07-2005) training at

Company.

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Acknowledgement:-

Practical training has an important role in a shaping up an engineering student for practical knowledge how a keeping him update with latest technology. First of all, I would like to express my attitude towards Mr. S.C.Gupta (Training cum placement officer, GPC, Kota) and towards Ms. Rajul Goyal (H.O.D., Electronics department, GPC, Kota) for providing me a great opportunity to undertake training at BSNL, Kota.

I would also like to thanks to Mr. Rajkishore Sharma (TTA EWSD, Nayapura, Kota) and the co-operative management helpful staff for giving me a knowledge of their services and helping me time to time.

Last but not least I would like to thanks to training incharge Mr. R.P.Manthwal (SDE SDOP1, KOTA), BSNL, Kota for arranging the training programmer for my practical training.

With extreme regards and obligations.

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CONTENTS: -

1) INTRODUCTION2) COMPANY PROFILE3) PROFILE OF THE COMPANY’S BUSINESS

A. GLIMPES OF MAIN SERVICE OFFEREDi. BASIC AND LIMITED MOBILE TELEPHONE SERVICES

ii. CELLULAR MOBILE TELEPHONE SERVICESiii. INTERNET SERVICESiv. INTELLIGENT NETWORK

v. IP TV SERVICESvi. THIRD GENERATION 3G WIRELESS TECHNOLOGY

B. DEVELOPMENT OF RURAL TELECOM NETWORKi. Rural DELs

ii. Village Telephonesa) Village Public Telephones (VPTs) & RCPsb) Public Telephones:-

C. NETWORK MANAGEMENTD. Setting up KU Band VSAT networkE. Policy on transmission network maintenanceF. Annual Maintenance contracts for switching system & WLL

G. COMPUTERISATIONH. OBLIGATIONS

i. Towards customers and dealersii. Towards employees

iii. Towards the Society –Corporate Social Responsibilities

1) STRUCTURE AND ABOUT THE EXCHANGES

i. COMPUTER UNITii. POWER PLANT

iii. AC Plant (CENTRAL AIR CONDITIONER)iv. MDF (MAIN DISTRIBUTION FRAME)

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2) CONNECTING SYSTEM

3) EWSD EXCHANGE1. GENERAL OVERVIEW2. INTRODUCTION OF EWSD3. FUNCTIONAL BLOCK DIAGRAM OF EWSD4. GENERAL FEATURES5. POSITION AND FUNCTIONAL STRUCTURE6. CAPACITY STAGES7. FUNCTIONAL UNIT OF SN8. SWITCHING NETWORK (B)9. RACK ASSIGNMENT10. MODULE FRAME LAYOT11. INTERCONECTIONS OF SWITHING MODULE12. FUNCTIONS13. O&M ASPECTS14. EXCERCISES 15. SWITCHING TECHNIQUES

4) INTERNET 5) CELLULAR MOBILE SERVICES

1. WLL (WIRE LESS IN LOCAL LOOP) MOBILE2. CODE DIVISION MULTIPLE ACCESS (CDMA) MOBILE3. GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM) 4. THIRD GENERATION (3G) TECHNOLOGY

6) BSNL’S IP TV7) CONCLUSION8) GLOSSARY OF TERMS AND ABBREVIATIONS

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Introduction:-

Today, BSNL is the No. 1 telecommunication company and the largest public sector undertaking of India and its responsibilities includes improvement of the already impeccable quality of telecom services, expansion of telecom services in all villages and instilling confidence among its customers.

Apart from vast network expansions, especial emphasis has given for introducing latest technologies and new services like I-NET, INTERNET, ISDN (INTEGRATED SERVICES DIGITAL NETWORK), IN (INTELLIGENT NETWORK), CDMA, GSM and WLL (WIRELESS IN LOCAL LOOP), BROADBAND, 3G services etc. Now BSNL has also entered in mobile communication. BSNL has all the new services send technological advantages, which are available with any well, developed Telecom network anywhere else in the country. Full credit for all above achievement goes to the officers and staff of the BSNL. The administration is fully aware of the challenges lying ahead and quite committed to provide the latest and best telecom services by their continued support and active co-operation.

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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 Training Center

(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.

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Different curriculum run in these centers to impart technology based training,

Training for Attitudinal change, basic educational and skill development

Program etc.

DOT: - Till 31st December, 1984, the postal, telegraph and telephone services were

managed by the Posts and Telegraphs Department. In January 1985, two separate Departments

for the Posts and the Telecommunications were created. The accounts of the department,

initially, were maintained by the Accountant General of the P&T. However, by April 1972, the

telecommunications accounts were separated. Simultaneously the department also started

preparing the balance sheet annually. With the takeover of the accounts from the audit and

delegation of larger financial powers to the field units, internal Financial Advisers were posted to

all the circles and units.

DEPARTMENT OF TELECOMMUNICATIONS (DOT) The Telecommunication Board consisted of the Secretary Telecommunications, who was the Chairman with Member (Finance), Member (Operations), Member (Development), Member (Personnel) and Member (Technology). The Telecom Commission was constituted in 1989. The Commission has the DoT Secretary as its Chairman with Member (Services), Member (Technology) and Member (Finance) as its full time members. The Secretary (Finance), Secretary (DoE), Secretary (Industries) and Secretary (Planning Commission) are part time members of the Commission. The Department in 1986 reorganised the Telecommunication Circles with the Secondary Switching Areas as basic units. This was implemented in a phased manner. Bombay and Delhi Telephones were separated to create the new entity called Mahanagar Telephone Nigam Ltd. (MTNL). On 1st October 2000, Department created BSNL, a new entity to operate services in different parts of the country as a public sector unit.

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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 i.e. 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 Authorized 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

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VISION To become the largest telecom Service Provider in South East Asia.

It is defined as an organization’s dream, which it wants to realize in the long run say

5-10 years time frame.

A dream which a company sincerely attempts to make a reality.

While it is not necessary to have a Vision statement, it makes sense to have one so that all efforts, energy and resources get directed in realizing this Vision.

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.

Mission is the path taken to realize the Vision. For example if leading a prosperous life after graduation is the vision of parents for their son, mission could be to get the son admitted in an engineering college so as to realize that vision.

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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 31 st Jan. 2006 out of which 1.16 Crore

cellular telephones are in the prepaid segment.

3. INTERNET SERVICESBSNL offers Dialup and Broad Band Internet services to the customers by Post-paid service with

the brand name ‘Net one’, 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

Corporate, 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.

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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.

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, Ahmadabad 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. IP TV Service

First started in Japan in 2002. Popular in France, South Korea, Germany, Hongkong etc., France is leading in IPTV having more than 1.7 million IPTV viewers, Global IPTV subscribers base will reach 14.5 million in 2007 and will be approximately 63 million by 2010.

6. Third Generation (3G) Wireless Technology

Capability to support circuit and packet data at high bit rates:

144 kilobits/second or higher in high mobility (vehicular) traffic

384 kilobits/second for pedestrian traffic

2 Megabits/second or higher for indoor traffic

Support of multimedia services/capabilities:

Fixed and variable rate bit traffic

Bandwidth on demand

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Asymmetric data rates in the forward and reverse links

Multimedia mail store and forward

Broadband access up to 2 Megabits/second

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.

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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, especially with regard to cellular services. BSNL has more than 4.7 Lakhs Route Kilometers of optical fiber 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.

What is V-SAT?

It can be defined as a class of very small aperture Intelligent Satellite Earth Station suitable for easy on-premise installation, usually operating in conjugation with a large size HUB earth station. Capable of supporting a wide range of two ways integrated Telecom Services.It has the following components:Micro Earth StationMini Earth StationPersonal Earth StationRoof Top TerminalCustomer Premises Terminal

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ADVANTAGES OF V-SAT

Can be located in the user premises on roof top or backyard and hence eliminate last mile problem.Superior quality satellite based data services.Quick implementation time.Reliable communication.Broadcast feature on satellite communication.Communication to different areas.Flexibility for network and changes.Service in distance insensitive.Low cost.

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 formalized. Telecom Territorial Circles are also being connected with computerized 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.

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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

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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.

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STRUCTURE AND ABOUT THE EXCHANGES

All telephone subscribers are served by automatic exchanges, which perform the functions the human operator. The number being dialed is stored and then passed to the exchange’s central computer, which in turns operates the switching to complete the call or routes it a higher level switch for further processing. Today’s automatic exchanges uses a pair of computers, one running the program that provides services and the second monitoring the operation of the first, ready to take over in a few seconds in the event of equipment failure.

Various exchanges present in BSNL are: C-DOT E-10B OCB283 (Exchange & TAX) EWSD (Exchange & TAX)

All exchange has some purposes and some basic structural units, which are:

1. subscriber’s connection unit 2. Switching network (CX) 3. Control unit 4. OMC (Operational & maintenance Control)

STRUCTURE OF THE EXCHANGE

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OMC

Room

Switch

Room

M.D.F.(Main Distribution Frame)

ETM(Translator and Interpreter)

Exploitation Room

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For smooth working of an exchange following unit are very important: -

1. Computer Unit: - it deals with additional services of the exchange to the customers with the help of computers.

2. Power Plant:- to feed proper power supply to exchange

3. AC Plant: - to maintain the continuous temperature + or – 2 degree Celsius to the digital switch (exchange).

4. MDF: - to connect switch (exchange) with the external environment (subscriber) i.e. it is the interface between subscribers and exchange.

1. Computer unit: - as the name specified it is the main part of the exchange that deals with the all services provided by the exchange to the customers with the help of computer. It also provides the updated data to all other part of the exchange.

The customers are using the services of the exchange by using the internet also gets connected to the main server present this room via an internet room.

It mainly consists of the servers that are providing the different services. The main servers of this room are:-

IVRS is used for the change number services provided by the exchange. CERS are provided by the exchange to avoid the problems that the users are facing the repairing of telephone. In this system when the user enters its complained it gets directly entered to the server and user is allotted with an id number.

LOCAL DIRECTORY ENQUIRY is another services provided by the exchange, by using this; subscribers calls the particular number and gets the directory enquiry. The server present in the main computer room provides this service.

INTERNET DIRECTORY ENQUIRY is the latest service by the exchange. In this type of service makes it enquiry using the internet, which gets connected to the main server at the internet room in the exchange and further to the main server in the computer room.

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2. POWERPLANT: -As we know that, the power is the main source or any organization. It is the case of E-10B

exchange. That is the first requirement of any organization is the input.The main source of this exchange is AC supply. However, as soon as the power supply is gone off, then what is source? No one think on this that the telephone is always plays its role in the human life. Even if the power supply gone off. Thus there must be adjustment source of power.

The main parts of the power room are: -i. Batteries: - these are the instant sources of the power as soon as power is gone off.

ii. Charging- Discharging Unit: - the batteries we are using in the power room need timely charging. As soon as the AC power supply is on, we make use of the charging unit present in the power room. The slowly charging of the batteries is known as the trickle charging. But sometimes we need the BOOSTER charging. In this type of charging awe take of the batteries from the load and charge separately, until it gets fully charged.The main work of the discharging unit is to control the discharging of the batteries.

iii. Inverter and Converter Unit: - the main use of this system is to change AC mains to DC and vice versa as required by the parts of exchange.

iv. Engine Room:-we know that the batteries are the instant source of supply but we cannot use it for much larger time, thus for this, we have an engine to generate the power supply. They are of 885 KVA. Thus, this room controls the supply of the engine.

UPS OPERATING MODES :

UPS system has three operating mode which can be designated as

1. Normal mode

2. Emergency mode

3. Recovery mode

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I. NORMAL MODE:

The rectifier charger draws power from the ac mains & convert it into DC. This DC power is

supplied to the inverter which converts it back into AC power to feed the critical load connected to the

output of the inverter. A small amount of DC owner is also supplied to the battery which is connected to

the output of the rectifier charger. The battery is thus kept in a fully charged condition by the rectifier

charge. In this condition the battery is said to be on float across the rectifier charger.

In this mode the battery does not supply any power to the inverter.

II. EMERGENCY MODE: -

Emergency mode occurs when there is an interruption in the AC input to the rectifier charger.

Interruption like voltage dips below the limit acceptable to the rectifier charger to fall. But the input of

the inverter cannot fall because the battery is across inverter input & it maintains the voltage. AC mains

is interrupted, the source of the inverter input current gets instantaneously transferred from the

rectifier charger to the battery when the output voltage generated by the rectifier charger falls below

the battery voltage. The battery which was earlier on float (charged) instantaneously goes into discharge

& then supplies power to the inverter till the AC mains resumes or the battery gets fully discharged.

During this mode current cannot flow back from the battery into the AC mains because the voltage

reverse biases the diodes or THYRISTORS in the rectifier charger.

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III. RECOVERY MODE:

The recovery mode commences when the AC mains resumes after the interruption. When the

generated voltage of the rectifier exceed the battery voltage. The input current of the inverter gets

instantaneously transferred from the battery to the rectifier charger. During this mode the rectifier

charger not only supplies power to the inverter but also supplies charging current to the battery to

restore the charge lost by the battery during the emergency mode. When the battery gets fully charged,

the charging current decreases progressively and the battery reverts to the float mode and the UPS to

the normal mode.

The duration of the recovery mode depends on the extent of battery discharged, approximately

10 to 20 hours depending on the battery specifications and the design of the rectifier charger.

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3. AC PLANT (CENTRAL AIR CONDITIONER)

for the function of electrical equipment, cooling system is basic requirement. The basic advantages of cooling systems are following- It provides the thermal stability so that the temperature does not reach the tolerance limit of electronic equipment. It saves equipment from dust so to avoid malfunction of equipment’s.It protects equipment from excess humidity which can caused rusting of equipment.

The basic unit of measurement used in the industry is known as “ton of refrigeration” (TR) which is equivalent to the heat extracted in 24 hours for converting thousands kg of liquid to ice at zero degree. The compressor is the heart of the AC system and the costliest. It increases the pressure and temperature of the refrigerant gas coming from the evaporator coils by compressing it.Compressor comes in various types. The most widely used is simple reciprocal type a cylinder and piston arrangement. For capacity more than 120 TR, centrifugal compressors are used. The condenser liquefies the refrigerant gas by a heat exchange process. The capillary tube or the expansion valve pressurizes liquid refrigerant and meters it flows to the evaporator.The refrigerant then passes through the evaporator coils, which extract heat out of the ambience.

4. MAIN DISTRIBUTION FRAME

The primary function of MDF is: - The fault of telephone number is removed in the MDF; it is called as Fault Remove Section. For removing the fault of telephone number, we use the testing these testing are T.T.Y. testing, Group testing, etc. For any type of testing firstly we need the vertical no. or the live tester, printer and computer test N.E. number of that particular telephone number.The telephone numbers are also disconnected in the MDF because of some specific reason.

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ORGANISATION OF THE MDFPARTS OF THE MDF

Horizontal sideVertical side

a. HORIZONTAL SIDE:It is again subdivided in to two partsExchange sideLine side

Description of the horizontal side:-

RACK: - On the rack, the tags are situated. One rack is having eight tags. The courting is done from up (0) to down (7).

TAG: - Each rack consists of eight tags.1 tag = 4 core1 core = 4 bunch1 bunch = 2 line

N.E.:- The word NE stands for the ‘NUMBER OF EQUIPMENT’.It is a 128 pair cable. The EWSD and MDF connected by NE.

WEDGE:-If we want to disconnect any two numbers then we insert a wedge between subscriber side and exchange side. Here wedge works as insulator made of plastic.

a. VERTICAL SIDE:

The vertical aside connected to the underground cable. This cable is having 100 pairs.These pair is distributed when we allot the telephone number to the subscriber.Vertical side is again subdivided in two parts:

One part is connected with the horizontal side and another with the subscriber line by using 100 pair underground cable.

This is how the present day telephone system works. Different exchanges have different architectures of switching call routing and other features.

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FUNCTION OF MDF: -• A fixed means of terminating the external cables.• A means for mounting the protective devices for incoming circuits.• A convenient point of interception for locating of faults.• A means for cross connecting the external circuits to the appropriate

Internal circuits.The MDF is properly earthed for the protection of the equipment. The external

pairs are area wise terminated on the line side of the frame, while connection fromthe equipment is done on the exchange side in a numerical order. Byinterconnections at this frame with the help of jumper wires, any subscriber in anyarea can be given any exchange number. This MDF mounts Delay Fuses only.

PROTECTIVE DEVICES : -Comprehensive protection against effects of lightning

and power line contacts, is achieved in practice by fuses, arresters and heat coils.They are not affected by normal speech and signaling voltage and current butoperates when the foreign voltage or current on the line is excessive. The line isthen disconnected automatically from the equipment or a connection to earth isFor safety precautions fuses are used. Every subscriber line has individual fuse.These fuses are made of GD (gas discharge) tube, which are connected in parallel.These fuses have two sides, one is exchange side and other is subscriber side.Connections between the different tag blocks are made using the jumper wires ofred and white colors.

GD tubes are connected in parallel while electrical fuses are connected in series.In electrical fuse, when high voltage appears across it, then it will break up theConnection and thus safeguard the system. If GD tube is connected in series, thendue to high voltage across any line, the whole exchange will be disconnected.Thus when GD tubes are connected in parallel, it will provide the requiredfacility.

GASE DISCHARGE PROCTECTORS: -

In case of heavy lightning discharges,gas discharge protectors are used and more consistent voltage is obtained. The gasdischarge protector essentially consists of two tungsten electrodes sealed in aspecial glass envelope containing a mixture of inert gases, mainly neon. One ofthe electrodes are for connections to the lines and the other is the earth electrode.

If the potential difference across the electrodes rises to a certain critical value (theStriking value) the gas is ionized and becomes conducting. This condition willContinue till the potential difference across the electrodes falls to the extinctionvoltage value. For voltages less than striking value it will not conduct. For normaloperating voltages on the lines, it offers extremely high impedance and thus does

27

2009



not introduce any transmission loss.For equipment side:

MDF has many tag blocks of 100 and that numbered from 1 to 100.In a tag block, there are 128 pair wire theoretically. Therefore, total number ofConnecting wires are 1024 theoretically. But in practical, there are only 1000 pairs.For equipment side:

From ground, a single pair of 400 wires originates, which is dividedIn 4 pairs of 100 wires. Practically, each pair is provided with 102 wires. TheseExact 2 wires are used in case of any manufacturing defect.For broadband connections, different colored tag blocks are provided.Broadband is used to provide different facilities on land-line phones with highSpeed to access them. A grey colored tag block is used for line side while yellow

Colored tag block is used on equipment side. These tag blocks has 0 to 47 pairs.In order to know the centre load point.:Cabinet and pillar are provided with capacity as per requirement. The D.P. box isProvided with 10 or 20 or 5 pairs. Now a days, a D.P. box of 5 pairs is used whichis wall mount instead of being mounted on pole.

To identify any telephone, we require the following two addresses:-

1. Exchange/line address2. Equipment address

Exchange address is written in given manner:Vertical number-tag block number-pair numberFor example 7-5-15Here, vertical no.=7Tag block no.=5Pair no.=15This gives the address of a telephone in the exchange.Equipment address is given as:-Rack number-tag block number-pair numberFor example7-6-87Here,rack no.=7Tag block no.=6Pair no.=87This gives the information about the actual location of telephone equipment. Thisaddress is provided to lineman for repairing, in case of any fault.There is a section of fault repairing located in MDF section. Whensubscriber’s phone is not working, then subscriber call to exchange. For this hedial,198.

28

2009



CONNECTING SYSTEM

Exchange Side Line Side

Cables from all the Exchanges reach the MDF

From the MDF Underground Jumper Cables go to the Cabinets

* The Capacity of the Cabinets is large around 2000 pairs

* If the number of subscribers is small then there is no need for

the Cabinets

From the Cabinets the cables go to the Pillars

*the position of the pillars is chosen such that the length of the wires going to the DPs is equal

in all directions

From the Pillars the wires go to the DPs

* the capacity of each of the Pillars is about 10 or 15

29

EXCHANGE MDF CABINETS PILLARS

DISTRIBUTION SUBSCRIBERS

2009



From the DPs the wires go to the subscribers’ homes

When a fault like Phone dead is reported then first check is made at the MDF

(i) a Phone Set is inserted on the Line Side, some number is dialed and it is checked if the

conversation takes place properly

(ii) if the conversation takes place properly then the fault is said to be on the Line Side

(Outdoors)

(iii) But if there is no Dial Tone then the fault is said to be on the Exchange side (Indoors)

The fault in the Outdoors is checked first of all at the DP

If there is dial tone at the Pillar but not in the subscribers home then the fault is in

between the DP and the subscribers phone set.

Otherwise at the Pillar If there is dial tone at the Pillar but not at the DP then the fault is

in between the DP and the Pillar

Otherwise the phone is checked at the Cabinet If there is dial tone at the Cabinet but

not at the Pillar then the fault is in between the Cabinet and the Pillar

Otherwise the only option left is that the fault is in between the MDF and the Cabinet

30

2009



EWSD

EWSD and Office Switch

1. General Overview

EWSD (Elektronisches Wählsystem Digital in German, Electronic Digital Switching System/Electronic World Switch Digital in English) is one of the most widely installed telephone exchange systems in the world. EWSD can work as a local or tandem switch or combined local/tandem, and for landline or mobile phones. It is manufactured by Siemens AG, who claims that EWSD switches perform switching for over 160 million subscriber lines in more than 100 countries.

DeTeWe bought its first EWSD under license in 1985 for remote switching. Bosch built its first EWSD as a local exchange in 1986. Deutsche Telekom, formerly Deutsche Bundespost, the largest German telephone company, uses EWSD and System 12 (Alcatel), the former more than the latter.

In 2007, Nokia Corporation and Siemens AG formed the new company Nokia Siemens Networks, and responsibility of further development and shipments of the EWSD system is dependent on this new company.

Contents

31

http://en.wikipedia.org/wiki/File:EWSD.jpg

2009



1 Hardware 2 Software 3 Technical data

Hardware

Main subsystems are:

CP (Central Processor) MB (Message Buffer) CCNC (Common Channel Network Control) LINE (Analog Line Group) LTG (Line Trunk Group) DLU (Digital Line Unit) SN (Switching Network)

All system units are redundant so the inactive side can take over immediately in case of an error.

DLU handles analog and ISDN lines and includes codec’s for analog lines, one of the BORSCHT functions for subscriber lines. Digital signals are assigned a time slot. DLU concentrates traffic onto a Line B unit, as well as Primary ISDN and V5.2 connections. Supervision and address signaling (dial pulse, DTMF) are also integrated in the DLU. For PCM-30 (E-1) connections to other exchanges, Line C Units are used, which also handle signaling including SS7, MFC R2 signaling, IKZ (dial pulse), and E&M.

he Switching Network consists of 4 space division stages of 16x16 switches, and a time division section with 16 stages of 4x4 switches. Control is provided by the CP Co-ordination Processor.

There are the following kinds of Co-ordination Processors:

CP103 with max 22,000 call attempts in the busy hour CP112 with max 60,000 call attempts in the busy hour CP113D with max one million call attempts in the busy hour CP113C with max six million call attempts in the busy hour CP113E with max ten million call attempts in the busy hour

Software

32

2009



The software of EWSD is called APS (Automatic Program System). The APS is on a hard drive and includes the operating system, developed by Siemens in cooperation with Bosch. It is predominantly written in the CHILL language. Application software is switch specific and serves among other things traffic management, path search, and call charging. Support software serves translating programs, binding modules as well as administration of libraries for generating data. Operating and data communication software serve for co-operation of maintenance centers and switching centers.

Technical data

Number of access lines: to 250,000 Number of feeder lines: 240,000 Traffic connection: 25,200 Call attempts in busy hour: 10 million Operating voltages: -48V -60V -90V Rate zones: 127, for each zone of 6 tariffs Tariff change-over at 15 minute intervals Space requirement with 10,000 access lines: 35 square meters 15-25 *C Temperature

EWSD EXCHANGE KOTA

33

2009



EQUIPPED CAPACITY 60K

DATE OF COMISSION

MAIN (NAYAPURA) - 6K 16.12.96

IST EXP - 4K 10.02.97

IIND EXP - 4.4K 18.03.97

3RD EXP - 2K 08.06.99

RSU NGM - 5.0 K 06-.11.97

RSUJN - 5.0K 26.03.98

RSUANP - 1K 20.10.98

RSUDDB - 5.5K 16.11.98

EQUIPMENT DETAILS

DLU - 11

RSU DLU - 65

LTG B - 132

LTG C - 57

CP 113A - 1

CCNP - 1

SNB - 2

MBICCG - 1

DEVO - 1

34

2009



OOF - 1

WRKING CONNECTIONS 43753

PBX LN 328

STD PCO 1212

ISDNBRA 197

Sr.NO. Exchange Name Capacity Number Scheme DLU

1 Main(Nayapura)

10000 232,2330,2331,2332,

10,150,160,170,180,,190,

35

2009



2333,2340,2341,2342,

2450,2451

200,210,220,230

2 NGM(New Grain

Mandi)

6000 2360,236690-130,

250

650

3 JN(Junction)

5000 2460,2464260

270-290,440-460.

4 RLY colony(Railway Colony)

2000 2465-2466 900-920

5 E-10B (Road No. 2) 700 2410-2412 300

6 DDB (Dadbari) 6000 2500-2505380-420

530-540

7. KUNHARI 2500 2370-2372 350-370

8. Ballabh Bari 3000 2390-2392800-820

730

9. Kaithuni Pole 2800 2385-2387750-770

700

10. RAMPURA 4500 2380-2384620-640

1150

11 Keshv Pura 2800 2400-2403930-940

780,710.

12. BSM(Bhama Shah

1000 2490-2492 330-340

36

2009



Mandi)

13. DCM 2000 2480-2481 590-610

14 SNP(Shrinath Puram)

3000 2470-2473470-490

500-510

15 Mahaveer Nagar 2000 2475-24761050-1070

140

16 Talwandi 2850 2405-24071000-1020

720

17 Vigyan Nagar 1000 2410-2412 1100-1110

18. Kaithun 2844 740

19. Veer Sawarkar Nagar

456 2477 6002/456-798

20. Borkheda A(1)&(2) 912 LEVEL OF MAINS6001/00-356

6001/1200-1656

21. Kherali Phayak 456 LEVEL OF MAINS 6001/456-798

22 Badgaon 456 LEVEL OF KUNHARI

6002/00-356

23. Borkhandi 500 28640-28643 6008/0/0,1,2,3,4

37

2009



24. Thathed 6005/0/0,1,2,3,4

25. Alaniya 6006/0/0,1,2,3,4

26. Rangpur 6007/0/0,1,2,3,4

27. Arandkheda 6011/0/0,1,2

28 Mandana28126-28127

28128-28129

6012/0,1,2

6015/0,1,2

29 Dara28150-28151

28152-28153

6009/0,1,2,3

6004/0,1,2,3

30. WLL Jaipur 6000/0/0-9CLOSED

31. Kota CORDACT 200 22010-22011 6003

2. INTROCDUCTION OF EWSD

38

DLU LTG(B)

LTG(C)

CCNC

MB

CCGSYP

OMT PRINTER

CP

MTUMDD

SN

Figure 1. Position of Switching Network in EWSD

2009



Switching network (SN) performs the switching function for speech as well as for messages in an EWSD exchange. For this purpose it is connected to LTGs and CCNC for speech/data and to CP (through MB) for exchange of control information. Switching network with ultimate capacity up to 63 LTGs is called SN DE4. For larger exchanges SN DE5.1 is used which can connect up to 126 LTGs. Similarly SN DE5.2 can connect up to 252 and SN DE5.4 up to 504 LTGs.

39

2009



3. BLOCK DIAGRAM OF EWSD

EWSD switching system structure chart

DLUDigital line unit

SLM(A,D,X,I) - subscriber line modules

DLUC - Digital line unit controller

LTGLine trunk group

SNSwitching network

SSNC Signaling system network control

CCNCCommon channel network control

MBMessage buffer

CPCoordinating processor

BAP - base processor CAP - call processor CMY - common memory IOC- I/O controller AMP - ATM bridge

processor B:CMY0(1) - common

memory access bus

CCGCentral clock generator

Net

Manager

Network management system

40

2009



4. GENERAL FEATURES

Switching network is provided in capacity stages SN: 63LTG to SN: 504LTG, i.e. up to 63 LTGs can be connected or, via other intermediate capacity stages, up to 504 LTGs can be connected. The modularly expandable SN has negligibly small internal blocking and can be used in EWSD exchanges of all types and sizes.

The self monitoring switching network uses a uniform through connection format. Octets (8 bit speech samples) from the incoming time slots are switched to the outgoing time slots leading to the desired destination fully transparently. This means that each bit of all octets is transmitted to the output of the switching network in the way that it appears at the input (bit integrity). For each connection made via the switching network, the octets have the same sequence at the output as at the input (digit sequence integrity). The switching network’s full availability makes it possible for each incoming octet to be switched at any time to any outgoing highway at the output of the switching network. The time slots used in switching network for making through-connections make up a 64 Kbit/s connection path.

All of the switching network’s internal highways have a bit rate of 8192 bits/s (Secondary Digital Carriers, SDCs). 128 time slots with a transmission capacity of 64 Kbits/s each (128x64 = 8192 Kbits/s) are available on each 8192 Kbits/s highway. Separate cables each containing several (eight or sixteen) such internal highways, are used for each transmission direction. All externally connected highways also have the same uniform bit rate.

The switching network combines the numerous switching network functions in a few module types. These modules work at very high through-connection bit rates; 8192 Kbits/s and some even at 32768 Kbit/s. For example 1024 connections can be switched simultaneously through a space stage with 16 inputs and 16 outputs. Although these highly integrated switching network modules switch a large number of connections with a high degree of reliability, the EWSD switching networks are always duplicated. The amount of space needed for the switching network in the EWSD exchange is still very low despite this duplication.

Two different switching network versions have been supplied in India:

* Switching network [SN] supplied with first 110K order.

* Switching network B [SN (B)] supplied with subsequent orders.

41

2009



5. Position and Functional Structure

Switching network is connected to LTGs and CCNC for speech/data and to CP (through MB) for exchange of control information. Figure 1 shows the position of switching network in EWSD exchange with reference to other equipments.

For security reasons, entire SN is duplicated. The two sides of SN (SN0 and SN1) are called planes. The external highways for both transmission directions i.e. between the switching network and one LTG or between the switching network and one Message Buffer Unit (MBU) are identified as follows as shown in figure 2.

* SDC: LTG interface between SN and LTG: time slot 0 for message exchange between the LTG and coordination processor (CP) as well as between two LTGs, time slot 1 to 127 for subscriber connections.

* SDC: CCNC interface between the SN and the common channel signaling network (CCNC): for common channel signaling.

* SDC: TSG interface between SN and a message buffer unit assigned to CP (MBU: LTG) for message exchange between the CP and the LTGs as well as between the LTGs.

* SDC: SGC between the SN and an MBU: SGC of the CP for setting up and clearing connections.

Switching network in EWSD exchanges uses time and space switching and therefore it is functionally divided into Time Stage Group (TSG) and Space Stage Group (SSG). SN DE4 with capacity stage SN: 63LTG has a TST structure and TSG/SSG division is not applicable in this case.

TSGs and SSGs are interconnected through internal 8 Mb/s interfaces called SDC:SSG. TSGs of both planes are connected to SSGs of both planes, and thus these provide further security.

Each TSG and SSG have its own Switch Group Control(SGC) that is connected to CP via MB through interfaces SDC:SGC.

42

LTG 1

LTG n

CCNC

CP

MBU

MBU

MBU

SPACE STAGE GROUP

OFSN:DE5

TIME STAGE GROUP

OFSN:DE 5

OR

SN:DE4

SGC

SGC

Figure 2: SN Internal and External Interfaces

SDC:LTG

SDC:LTG

SDC:CCNC

SDC:TSG

SDC:SGC

SDC:SGC

SN

MB

SDC:SSG

SDC:SSG

2009



43

2009



TABLE 1: SN Capacity Stages

Capacity stages of

switching network

SN:63LTG

(DE 4)

SN:126LTG

(DE 5.1)

SN:252LTG

(DE 5.2)

SN:504LTG

(DE 5.4)

Switchable traffic(E) 3150 6300 12600 25200

Local Exchanges

No. of lines 30000 60000 125000 250000

Transit Exchanges

No. of trunks 7500 15000 30000 60000

Structure TST TSSST TSSST TSSST

Connectable no. of

LTGs or

LTG+CCNC

63

or

62+1

126

or

125+1

252

or

251+1

504

or

503+1

6. Capacity Stages

The present version of SN is available in capacity stages SN:63LTG, SN:126LTG, SN:252LTG and SN:504LTG. Modular structure permits partially equipped SN. Up gradation from DE5.1 to DE5.2 and from DE5.2 to DE5.4 is possible with the help of supplier. SN DE4 is not upgradable to DE5.1 as TSG and SSG are not separately identified in SN DE4. The traffic handling capacity, connect ability for various capacity stages of SN are shown in Table 1.

44

2009



7. Functional Units of SN

7.1 Switching path

The switching network is subdivided into time stage groups (TSG) and space stage groups (SSG). Due to its modular structure, the EWSD switching network can be partially equipped as needed and expanded step by step. The switching network uses the following switching stages:

one time stage incoming (TSI) three space stages (SS) and One time stage outgoing (TSO).

These time and space stages (functional units), shown in figure 3, are located in the following module types:

Link interface module between TSM and LTG (LIL) time stage module (TSM) link interface module between TSG and SSG (LIS) space stage module 8|15 (SSM8|15) space stage module 16|16 (SSM16|16)

The switching network capacity stage SN:63LTG, however has a TST structure with only one space stage as shown in figure 4. Module types LIS and SSM 8|15 are not there in SN:63 LTG. Further, the modules and the TSGs/SSGs are interconnected

A list of the various modules used in SN is given in Table 2.

45

Figure 4: The five module types in SN:DE4

LTG

MBU:SGC

SN1

SN0

LIL TSM SSM 16|16

SGC LIM

TSO

TSI

SSG1.0

LTG

MBU: SGC

TSG1.0

TSG0.0

LIL TSM LIS

SGC LIM

TS0

TSI

MBU: SGC

SSG0.0

LIS SSM 8|15 SSM16|16

SGC LIM

SSM15|8

SSM8|15

Figure 3: The seven module types in SN: DE5

2009



7.1.1 LIL & LIS:

The receiver components of the LIL and LIS compensate for differences in propagation times via connected highways. Thus, they produce phase synchronization between the incoming information on the highways. These differences in propagation times occur because an exchange’s racks are set up at varying distances to each other. Module LIL is connected on the interface to LTGs and has 4 inputs and 4 outputs while module LIS is connected on the interface to SSG and has 8 inputs and 8 outputs.

7.1.2. TSM:

The number of TSMs in a switching network is always equal to the number of LILs. Each TSM contains one time stage incoming (TSI) and one time stage outgoing (TSO) (Figure 5). The TSI and the TSO handle the incoming or outgoing information in the switching network. Between input and output, octets can change their time slot and highway via time

Stages. Octets on four incoming highways are cyclically written into the speech memory of a TSI or TSO (4x128 = 512 locations corresponding to 512 different time slots). The speech memory areas 0 and 1 are used alternately in consecutive 125- microseconds periods for writing the octets. The connections to be made determine the octet sequence during read-out. The stored octets are read-out to any one of 512 time slots and then transferred via four outgoing highways.

46

LIL

0

SSM16|16 or LIS

0

3

TSM

Figure 5 : Time stage module (TSM)

LIL

0

3

TSO

0

SSM16|16 or LIS

3

0

SSM16|16

14

0SSM16|16

14

SSM16|16

TSM or SSM8|15

0

15

0

TSM or SSM8|15

15

0

7

0

7

SSM8|15

SS 8|15

SS 15|8LIS

LIS

Figure 6 : Space stage modules (SSM16|16 and SSM8|15)

2009



7.1.3. SSM8|15 and SSM 16|16:

The SSM 8|15 contains two space stages as shown in figure 6. One space stage is used for transmission direction LIS SSM 8|15 SSM 16|16 and has 8 inlets and 15 outlets while a second space stage is used for transmission direction SSM 16|16 SSM 8|15 LIS and has 15 inlets and 8 outlets. Via space stages, octets can change their highways between input and output, but they retain the same time slot. Space stages 8|15, 16|16 and 15|8 switch the received octets synchronously with the time slots and the 125-microsecond periods. The connections to be switched change in consecutive time slots. In this process, the octets arriving on incoming highways are “spatially” distributed to outgoing highways . In capacity stages with a TST structure, the SSM 16|16 Switches the octets received from the TSIs directly to the TSOs.

47

2009



TABLE 2: List of Modules used in SN

PCB

No. of cards in SN:63

LTG

No. of cards in TSG of SN:DE5

No. of cards in SSG of SN:DE5

Remarks

LIL 16 16 - One LIL can connect up to 4 LTGs. The cards LIL and TSM

TSM 16 16 - are always used in pairs

LIS - 8 16 This PCB has 8 inlets and 8 outlets. LIS and SSM8|15

SSM8|15 - - 16 are always used in pairs

SSM16|16 4 - 15 Used to cross connect outlets of 16 SSM8/15 to inlets of SSM15/8

LIM 1 1 1

These two PCBs are used

SGC 1 1 1 in the SGC

DCC(B) 2 2 2 Separate shelf is provided for

the DCC(B)s in the rack

48

2009



7.2 Control section:

Each TSG, each SSG, and with SN: 63LTG, each switching network side has its own control. These controls each consist of two modules viz. switch group control (SGC) and link interface module between SGC and MBU: SGC (LIM)

An SGC consists of a microprocessor with accompanying memory and peripheral components. The main tasks of an SGC are to handle CP commands (such as connection setup and clear down), message generation and routine test execution. Apart from the interface to the message buffer unit (MBU: SGC), an LIM has a hardware controller (HWC) and a clock generator for clock distribution.

7.3Firmware

The firmware for the switching network is permanently stored in the program memory of each SGC. For this reason, it does not have to be loaded or initialized by the coordination processor (CP). SN firmware is organized in the following manner:

executive control programs call processing programs maintenance programs startup and safeguarding programs

49

2009



8. Switching network (B)

Switching network (B) is a special compact version of switching network wherein a number of functional units are integrated over a single module. This arrangement has the following advantages:

* Reduction in shelf space

* Reduction in number of PCB types

* Utilization of available space in SN rack for accommodating LTGs

Functionally SN(B) is entirely similar to SN. However, only the following five types of modules are used in SN(B) as shown in table 3.

TSMB: Two LILs and two time stage modules TSMs are combined to form one TSMB.

LISB: This is formed by combining two LIS functional units in a TSG.

SSM8B: Two LIS and two SSM8|15 functional units in a SSG are combined

to form one SSM8B.

SSM16B: This is formed by combining eight SSM16|16 functional units.

SGCB: Functional units LIM and SGC are combined to form one SGCB.

50

2009



TABLE 3: SN(B) Modules

PCB

No. of cards in SN(B)

:63LTG

No. of cards in TSG of SN(B):DE5

No. of cards in SSG of SN(B):DE5 Equivalent modules in SN

TSMB 8 8 - 2 X TSM +

2 X LIL

LIS - 4 - 2 X LIS of TSG

SSM8B - - 8 2 X LIS of SSG +

2 X SSM8|15

SSM16B 1 - 2 8 X SSM16|16

SGCB 1 1 1 LIM +

SGC

DCCMS 1 1 1 Provided in same shelf

containing SN/TSG/SSG

51

TSG0.x or SSG0.x or

SN0

*) duplicated time stage group (TSG), duplicated space stage group (SSG), or both SN:63LTG sides (SN0 and SN1)

Figure 7: Rack for Switching Network (R:SN)

*)

DCC(B)

Fuse Panel

TSG1x or SSG1x or

SN1

770 mm

2009



9. Rack Assignment

Both planes of SN: 63LTG are accommodated in two frames of a single SN rack. In case of SN: 126 LTG, both planes of TSG or SSG occupy one rack each. Thus there are two racks for 2 TSGs and one rack for one SSG. SN: 252LTG and SN: 504LTG have rack assignment similar to SN: 126 LTG and occupy 6 and 12 racks respectively. Rack assignment for SN is shown in figure 7.

In case of SN (B) both planes of SN (B) of SN DE4 and both planes of TSG or SSG of SN DE5 are accommodated in two frames of a single SN rack. However since each such frame consists of one shelf only, the balance space in the rack is utilized for accommodating LTGs. The SSG shelf can accommodate two SSGs. The composite rack is called rack for SN (B)/LTG. Rack assignment for SN (B)/LTG is shown in figure 8.

52

2450 mm

TSG0.x or SSG0.x or

SN0

*) duplicated time state group (TSG), duplicated space stage group(s) (SSG) or both SN:63LTG sides (SN0 and SN1)

Fuse Panel

F:LTG3

F:LTG2

F:LTG1

F:LTG0

TSG1x or SSG1x or

SN1

*)

Fuse Panel

F:LTG3

F:LTG2

F:LTG1

F:LTG0

*)

TSG1x or SSG1x or

SN1

TSG0.x or SSG0.x or

SN0

Figure 8. Rack for switching network B and line/trunk group (R:SN(B)/LTG) with cable lead-in from

top (left) and from bottom (right)

2009



53

LIL

SSM16|16

TSM

SSM16|

16

LI

M

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

LIL

SSM16|16

TSM

SSM16|

16

SGC

LIL

TSM

LIL

TSM

LIL

TSM

LIL

TSM

Figure 9: Module Locations (SN:63LTG)

SN0orSN1

2009



10. Module Frame Layout

10.1 SN:63LTG

One plane of SN:63LTG is accommodated in one frame consisting of two shelves. The arrangement of modules in module frame for SN:63LTG is shown in figure 9.

54

Supporting Plate

Figure 10 (a): Module Locations (TSG)

B

A

TSM

00

LIL

01

TSM

01

LIL

00

LIL

03

TSM

03

LIL

02

TSM

02

LIS

04

LIS

00

TSM

08

LIL

09

TSM

09

LIL

08

LIL

11

TSM

11

LIL

10

TSM

10

LIS

06

LIS

02

D

C

001006

011016

021026

031036

044 050 061

LIS

01

LIM

LIS

05

TSM

05

LIL

04

TSM

04

LIS

03

SGC

LIS

07

TSM

13

LIL

12

TSM

12

LIL

05

TSM

06

LIL

06

TSM

07

LIL

13

TSM

14

LIL

14

TSM

15

LIL

07

LIL

15

070 076 087092

097102

107112

117122

MOLOC

Row

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10.2 SN:126LTG and higher capacity stages

One TSG or one SSG of SN: 126LTG or above occupies one frame consisting of two shelves. The arrangement of modules in module frame for SN: 126LTG or above is shown in figure 10 (a) and (b).

55

Figure 10 (b): Module Locations (SSG)

B

A

D

C

001006

011016

021

LIS

11

SSM8/15

1

LIS

00

SSM8/15

00 L

IS

9

9

SSM8/15

99

LIS

88

SSM8/15

88

LIS

33

SSM8/15

33

LIS

22

SSM8/15

22

SSM16/16

14

SSM16/16

00

SSM16/16

32

SSM16/16

28

SSM16/16

55

SSM16/16

41

LIM

SSM8/15

44

SSM16/16

73

SSM16/16

69

SSM8/15

66

LIS

55

SSM8/15

55

LIS

44

LIS

66

SSM8/15

77

LIS

77L

IS

111

SSM8/15

111

LIS

100

SSM8/15

100

SSM16/16

96

SSM16/16

8

2

SSM16/16

114

SSM16/16

100

SSM16/16

137

SSM16/16

123

SGC

026031

036041 047

001053

057061

067073 079

083087

092097

102107

112117

122

SSM8/15

122

SSM16/16

141

SSM8/15

1446

LIS

1335

SSM8/15

1335

LIS

122

LIS

144

146

SSM8/15

1457

LIS

1557

MOLOC

2009



56

TSMB

TSMB

TSMB

TSMB

SGCB

LISB

LISB

TSMB

LISB

LISB

TSMB

TSMB

TSMB

DCCMS

Figure 11 (a): Module Frame for TSG(B) (F:TSG(B))

SSM8B

SSM8B

SSM16B

SSM8B

SSM8B

SSM16B

SSM8B

SSM8B

SSM8B

SGCB

SSM8B

SSM8B

SSM8B

SSM16B

SSM8B

DCCMS

Figure 11 (b): Module frame for two SSG(B) (F:SSG(B))

SSM8B

SGCB

SSM8B

SSM8B

SSM16B

SSM8B

SSM8B

DCCMS

TSMB

TSMB

TSMB

TSMB

SSM16B

TSMB

SGCB

Figure 12: Module Frame for SN(B):63LTG

TSMB

TSMB

TSMB

DCCMS

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10.3 SN (B):126LTG and higher capacity stages

One TSG or two SSGs of SN(B):DE5 (126LTG or higher capacity) occupy one frame consisting of one shelf only. The arrangement of modules in module frame for SN:126LTG or above is shown in figure11 (a) and (b).

10.4 SN (B):63LTG: - One plane of SN(B):63LTG requires one frame consisting of only one shelf. The arrangement of modules in the module frame for SN(B):63LTG is shown in figure 12.

57

TSC0 LIL0

LIL1 TSC1

LIL14 TSC14

LIL15 TSC15

LISB0

LISB1

LISB2

LISB3

SDC: LTG

0

1

2

3

4

5

6

7

56

57

58

59

60

61

62

63

0

1

2

3

0

1

2

3

0

1

2

3

0

1

2

3

0

1

2

3

TSMB-00

1

2

3

0

1

2

3

TSMB-70

1

2

3

0

1

2

3

0

1

2

3

0

1

14

15

0

1

14

15

0

1

0

2

3

14

15

0

1

2

3

0

1

14

15

TSGx-x

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58

Fig. Time Stage group internal connections

2009



11.Interconnection of Switching Modules

Switching modules in EWSD switching network are connected in a manner so as to ensure nearly full availability. One module LIL, which can handle highways coming from 4 LTGs is connected to 4 inlets of a module TSM on one-to-one basis. Thus these 4 highways coming from 4 LTGs undergo a T-switching function and are then connected to inlets of 4 different LIS modules. The 8 inlets of a LIS module are connected to outlets of 8 different TSMs. Two such groups form a Time Stage Group wherein 63 LTGs can be connected. The TSG has 64 outlets coming out of 8 LIS modules. The interconnection arrangement is shown in figure 13.

Eight outlets of LIS modules in TSG are connected to 8 inlets of LIS modules in SSG on one-to-one basis. One SSG consists of 16 LIS modules and therefore two TSGs can be connected to one SSG. There is again one-to-one connection between 8 outlets of LIS modules and 8 inlets of SSM8|15 modules. Fifteen outlets of SSM8|15 and 16 inlets of SSM16|16 are cross connected. Similarly 16 outlets of SSM16|16 and 15 inlets of SSM15|8 are cross connected. The interconnection arrangement within SSG is shown in figure 14.

All the TSGs of SN are connected to all the SSGs in such a manner as to ensure nearly full availability. The interconnection of TSGs with SSGs in case of SN:504 LTG is shown in figure 15, and that for SN:252 LTG and SN:126 LTG are shown in figure 16.

Interconnection of the modules in SN DE4 is simpler as there are no TSG or SSG. The TSMs are directly connected to SSM16|16 as shown in figure 17.

59

LIS

0

0

7

8 15

SSM

0

To inputs 0 of SSM1-13

1

13

0

7

16 16

SSM

0

0

15

LIS0

7

8 15

15 15

To inputs 15 of SSM1-13

1

13

0

7

16 16

140

14

0

15

SN1

SN0

MBU:SGC

LIM SGC

Figure 14: Space Stage Group Internal connections

2009



60

2009



61

SSGx.0

LIS01234567

TSGx.0

01230123

TSGx.1

0LIS123456789101112131415

TSG1TSG2

TSG3

TSG4

TSG5TSG6

SSGx.0

TSGx.2

01230123

01230123

TSGx.3

0LIS123456789101112131415

TSG1TSG2

TSG3

TSG4

TSG5TSG6

SSGx.0

TSGx.2

01230123

01230123

TSGx.3

0LIS123456789101112131415

TSG1TSG2

TSG3

TSG4

TSG5TSG6

SSGx.0

TSGx.2

01230123

LIS01234567

> SSG

TSGx.3

0LIS123456789101112131415

TSG1TSG2

TSG3

TSG4

TSG5TSG6

Figure 15: TSG-SSG interconnection for SN: 504LTG

Figure 16: TSG-SSG interconnection for SN:252 and 126 LTG

0LIS123456789101112131415

SSGx.0

LIS01234567

TSGx.0

LIS01234567

TSGx.0

TSGx.1

LIS01234567

TSGx.0

0LIS123456789101112131415

SSGx.001230123

TSGx.2

01230123

LIS01234567

TSGx.3

TSG2

TSG1

TSG2

TSG1

0LIS123456789101112131415

SSGx.1

TSG2

TSG1

TSG2

TSG1

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63

Figure 18: Speech path of a through connection

SN

Space Stage Part 0

Space Stage Part 1

Space Stage Part 2

Space Stage Part 3CP MBU:

SGC

SGC/LIM

LTG of the calling party TSI

TSO

Setting command

TSM

TSM

LTG of the called party

TSI

TSO

2009



12. Functions

Three essential functions of switching network namely speech path switching, message path switching and changeover to standby are described below: -

12.1 Speech path switching

The switching network switches single channel and broadcast connections with a bit rate of 64 Kbit/s and multichannel connection with nx64 Kbits/s. Two connection paths are necessary per single channel connection (e.g. from calling to called party and from called to calling party). For a multichannel connection, nx2 connection paths are necessary. In broadcast connections, the information is passed from one signal source to a number of signal sinks (no opposing direction).

The coordination processor (CP) searches for free paths through the switching network according to the busy status of connection paths stored at that moment in the switching network’s memory. The path selection procedure is always the same and is independent of the capacity stage of the switching network. During path selection, the two connection paths of a call are always chosen so that they will be switched via the same space stage section. A space stage section is a quarter of the space stage arrangement; with an SN: 252 LTG, for example, this corresponds to half a space stage group SSG.

After path selection, the CP causes the same connection paths to be switched through in both switching network sides of an SN. The SGCs are responsible for switching the connection paths. In a capacity stage with 63 LTGs, one switch group control participates in switching a connection path; however in a capacity stage with 504, 252, or 126 LTGs, two or three switch group controls are involved. This depends on whether or not the subscribers are connected to the same TSG. The CP gives every involved switch group control setting instructions necessary for the through-connection. These setting instructions always have the same data format.

An SGC receives the setting instruction from the CP via the message buffer unit MBU: SGC, the secondary digital carrier SDC: SGC, n an SGC and the CP are exchanged via an LIM. The SGC calculates the setting data using the call processing programs and service routines. The SGC loads the data into registers in the hardware controller (HWC) of the LIM and, via the HWC, controls the setting of desired connection paths in

64

SN0

SN 1

TSG 1.0

LIL TSMLIS

E

S

TSO

TSI

SSG 1.0

LIS SSM8|15 SSM16|16

S

E

SSM15|8

SSM8|15

LTG

TSG0.0

LIL TSMLIS

E

S

TSO

TSI

SSG0.0

LIS SSM8|15 SSM16|16

S

E

SSM15|8

SSM8|15

Figure 19 :Example of possibilities for changeover to standby in the switching network capacity stage SN:504LTG, SN:252LTG and SN:126LTG

2009



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12.2 Message path switching.

Apart from the connections determined by subscribers by inputting dialing information, the switching network also makes connections between the LTG and the CP. These connections are used to exchange control information; they are setup only once, and then they are always available. For this reason, they are called semi permanent connections. Via these same connections, the LTGs also interchange message without having to burden the CP’s processing unit. In this manner, a separate line network for the exchange of messages within an exchange is not necessary. Nailed-up connections and connections for common channel signaling are made on a semi permanent basis as well.

12.3 Changeover to standby

All connection paths are duplicated, i.e. switched through in SN0 and SN1. This provides an alternative route for each connection in case of failure.

Figure 19 provides a simplified illustration of the various alternative routes possible in capacity stages with 504, 252, and 126 LTGs. The connection paths are switched in the same manner over both switching network sides (SN0 and SN1). The LTGs accept the incoming octets of the effective connections (subscriber/ subscriber connections) from only one switching network side. In figure 19, the effective connections lead over SN0. Of note is the duplicated routing between the time stage groups (TSG) and space stage group (SSG). This makes it possible for the TSGs and SSGs to be individually switched over to standby. Switching over to standby is implemented only if errors occur simultaneously in both switching network sides. The effective connections are then lead over routed TSGs and SSGs of both switching network sides 0 and 1. In the switching network capacity stage with 63 LTGs, it is only possible to route the connections over SN0 or SN1.

If an error occurs in the switching network, the CP initiates corresponding measures for switching over to standby and issues the corresponding messages. Changeover to standby do not interrupt existing connections. Thanks to this duplication principle, all operational measures are easily carried out without impairing traffic (e.g. adding new modules or replacing defective modules).

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13. O&M Aspects

The following MML commands are used during operation and maintenance of switching network.

Display and Modification in number of TSMs.

DISP TSG MOD TSG

Status display and Configuration commands

STAT SN CONF SN CONF TSG CONF SSG

Diagnosis and Test commands - SN DE4 and DE5

DIAG SN TEST SN

Diagnosis and Test commands - SN DE5 only

DIAG TSG DIAG SSG

TEST TSG TEST SSG

13.1 Safeguarding Concept

The switching network (SN) is duplicated. Normally one SN side is active (the SSG and both TSGs in ACT), and the other SN side is standby (the SSG and the TSGs in STB).

In the event of a malfunction in a switch group (SSG or TSG) in the active SN, the affected switch group is configured to UNA and the other switch groups in the previously standby SN are configured to ACT.

N the event of a malfunction in a switch group in the standby SN, only the affected switch group is configured to UNA.

None of these reconfigurations affect switching traffic.

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13.2 Fault Printouts

An SN fault printout is the result report of the fault analysis program for the SN or for a switch group (SSG or TSG). It complements the more general alarm signaling with SYP etc. i.e. whenever the safeguarding system detects a malfunction in the SN, an appropriate fault printout is formulated, typically as follows:

SN FAILURE WITH CONFIGURATION MMN:SN0xx-000

SGC DEFECT

FAULT LOCATION : TSG-side-tsg SGC

CONFIGURATION : TSG-side-tsg FROM : zzz TO : UNA

SUPPLEMENTARY INFORMATION :

H ‘zzzzzzzz zzzzzzzz zzzzzzzz zzzzzzzz

H ‘zzzzzzzz zzzzzzzz zzzzzzzz zzzzzzzz

Faults affecting the SN can be divided into two groups which are clearly distinguishable in terms of the system response: -

* Unconditional fault

These are serious faults. The switch group in which such a fault occurs is always reconfigured to UNA. With unconditional faults, the following codeword’s may be output :

- SGC/SGC FAILURE

- SGC/HWC FAILURE

- PATH SET/HWC-FAILURE

- CYCLE DEFEKT

- NO CYCLE

- SGC CHANNEL ERROR

* Conditional faults

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These are not serious. If such a fault occurs in a switch group with no redundancy (i.e. where the partner switch group is in NAC, UNA or MBL), then the affected switch group is not configured to UNA. If the switch group is duplicated, then it is configured to UNA, even for a conditional fault. Codeword’s for conditional faults are :

- SGC/PLLU-FAILURE

- SN-PLL FAILURE

- PATH SET/TSM-FAILURE

- PATH SET/SSM8-FAILURE

- PATH SET/SSM16-FAILURE

- SGC-DEFECT

- All COC-FAILURE

- All MCH-FAILURE

- All MUX-FAILURE

13.3 Diagnostics

Explanation: -

* DIAG TSG

This command starts a test program, to be specified under parameter TA, for a time stage group (TSG).

* DIAG SSG

69

DIAG TSG: SN=side, TSG=tsg,TA=area, SUBUNT= TSM/ SSM/ CSM - x;

2009



This command starts a test program, to be specified under parameter TA, for a space stage group (SSG).

* side SN plane, either 0 or 1

* tsg Number of TSG, 0 to 7

* TA (test area = test program)

* Area

The identifier entered for the parameter TA specifies the test program to be called up. The following test programs are possible: CHALL, ALL, HWC, TSM, SSM, CSM, PLL

In test program TSM, SSM and CSM, in the diagnostic command, a subunit must also be specified.

- CHALL (check all)

- For TSG, tests central sections,

CPU with program and data memory

PLL supervision circuit

hardware controller

tests decentralize sections :

control memory of TSM modules

- For SSG, tests central sections :

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CPU with program and data memory

PLL supervision circuit

hardware controller

tests decentralize sections :

control memory of SSM16|16 and SSM8|15

- ALL (check all control memories)

- For TSG, The control memories of modules TSM are tested.

Each bit in a control memory is checked for 1 and 0.

The addressing of each Ram chip in a control memory

is also checked.

- For SSG The control memories of modules SSM16|16 and

SSM8|15 are tested. Each bit in a control memory is

checked for 1 and 0.

The addressing of each RAM chip in a control memory is also checked. Whereas modules SSM8|15 are only tested according to the SN capacity stage specified in the CP command, all 15 SSM16|16 modules are tested.

- HWC (HWC test) - for TSG and SSG

The HWC registers are checked. A good or bad message gives the states of the HWC registers and the interface between SGC and HWC. The HWC interface to the switching modules is not tested.

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- TSM (TSM test)

The addressing and functioning of each bit in the control memory of a TSM module are tested.

- CSM (SSM16|16 test)

The addressing and functioning of each bit in the control memory of an SSM16|16 module are tested.

- SSM (SSM8|15 test)

The addressing and functioning of each bit in the control memory of an SSM8|15 are tested.

- PLL (PLL supervision circuit test)

* SUBUNT

For diagnostic identifiers TSM, CSM & SSM, the subunit must be specified.

Possible subunits are: TSM = functional unit TSM/LIL

SSM = functional unit LIS/SSM8|15

CSM = SSM16|16

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* X TSM number (0 to 15)

SSM8|15 number (0 to 15)

SSM16|16 number (0 to 14)

13.4 Test

The SN speech path test makes a cross-office check per SN side, switch group or subunit, depending on the command.

This involves setting up connections via SN, which are then tested with a test pattern. If the SN speech path detects a COC error in such a connection path, the test is repeated with a new path setup attempt (with the same parameters). If the test again detects a COC error, it is terminated with FAILURE DETECTED. The MML command used is as follows, where symbols/parameters are same as in DIAG SN.

73

TEST TSG: SN=side, TSG=tsg, TA=area, SUBUNT= TSM/ SSM/ CSM - x;

2009



14. Exercises

1. Interrogate and find out the capacity stage of SN in your exchange. Identify its racks, frames and modules.

2. Find out the number of LTGs and TSMs in your exchange and correlate. How many additional LTGs can be provided with the existing SN configuration?

3. Change status of both planes of SNs, one by one, using all possible combinations of OST and tabulate the results.

4. A fault in SN plane 0 has affected the third LTG connected to TSG1. What functional unit in SN could be faulty? Write MML commands to configure and diagnose the faulty unit.

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SWITCHING TECHNIQUES

SPACE DIVISION SWITCHING

MULTIPLE STAGE SWITCHING

TIME DIVISION SWITCHING

TWO-DIMENSIONAL SWITCHING

MULTI STAGE TIME AND SPACE SWITCHING

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INTERNET

Introduction:

The Internet is not a program, not software, not hardware or a big system. It is a group of various co-

operating computers worldwide interconnected by computer based on TCP\IP communication

protocols. People use it to get information over a standard communication link. The hundreds or

thousands or millions of computer network are connected to each other for exchanging the information

which is based on the unique identity and set of procedures. Internet is a series of interconnected

networks providing global link to information.

GIAS: BSNL launched the Gateway Internet Access Service (GAIS) through dial up/leased/ISDN network.

Users can access GAIS from 99 cities in India by this means.

INTERNET CONNECTIVITY

INTERNET TECHNOLOGY

The basic function of Internet can be summarized as under-

Interconnecting of computers to form a network.

Interconnecting of computers to form a network of networks.

To establish a communication link between two computers within as network.

To provide alternate communication link among the networks, even if one network is not working.

These are based on TCP/IP communications protocol.

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Transfer of a file through Internet:-

Suppose a file is to be transmitted on Internet from one computer to other ones

Break the file in to small packets

Attached destination and source address in o packets

Multiplexed and transmit these packets

At destination de-multiplex the packets

Remove address bits from the packets and assemble the data in to the original file

Make source bits as destination address and send the acknowledgement in to the source

Therefore, it is clear that network hardware sends the packets to specified destination and network

software reassembles of communications, the computer network performs the following functions-

Addressing and routing

Fragmentation and error correction

Data error checking

Connectivity control

Multiplexing and de-multiplexing

Data flow control

End users interface etc.

The data handling

A single module cannot handle the entire process. One that adopted as a standard is an open system

interconnection (OSI) model.

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COMMON TERMINOLOGY USED IN INTERNET:

WWW:

World Wide Web (WWW) is a wide area hypermedia information retrieval aiming to give

universal access to a large universe of documents.

HTTP:

Hyper text transmission Protocol (HTTP) is the communication protocol used to transfer

documents from the server to client over the WWW (http:// www).

HTML:

Hyper Text Markup Language (HTML) is a system of marking or tagging the various parts of web

documents to tell the browser software how to display the document text, link graphics and

link media.

ISDN:

Integrated Service Digital Network (ISDN) is a digital phone connection technology that provides

both voice and data services over the same connection.

ISP:

Internet Service Provider (ISP) is an agency that provides Internet access and other net related

services.

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NATIONAL INTERNET BACKBONE (NIB)

Networking is a key component of any Internet Services Provider (ISP) operations. The networking

equipments like access servers, routers and modems are critical to the successful functioning of ISP.

An ISP node where subscribers enter internet, consists of a set of equipments as given below.

Access server

Router

Modem bank

LAN (Local Area Network) components

Security server

Rack, console & power supply

Network management agent.

Help desk

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CELLULAR MOBILE SERVICES: -

Cellular is one of the fastest growing and most demanding telecommunication applications. Today, it

represents a continuously increasing percentage of all new telephone subscriptions around the world.

Currently there are more than 45 million subscribers in worldwide and nearly 50% of those subscribers

are located in USA. It is forecasted that cellular system using a digital technology will become the

universal method of telecommunications. By the year 2005, forecasters predict that there will be more

than 100 million cellular subscribers worldwide.

1. WIRELESS IN LOCAL LOOP (WLL) MOBILE

WLL is a communication system that connects customers to the Public Switch Telephone

Network (PSTN) using radio frequency signals as substitutes of conventional wires for all part of

connection between the subscribers and the telephone exchange. It works on CDMA technique.

The local loop is access part of telecommunication network i.e. the part between PSTN switch

and subscribers. WLL network application involves uses of radio to replace of the wire link

between PSTN switch and subscriber. The radio technology is able to provide same quality of

services as that provided by the wires line. Application of wireless loop technology has just been

started in the worldwide. There is no standard for this so far. However, a number of national

and international air interface standards for digital cellular mobile telephone system are

available.

TECHNICAL ASPECTS:

WLL is based on CDMA technique and is entirely different from GSM. The system for

WLL services can be divided in two following parts:-

BSC (Base Switching Centre):- It provides links between BTS & BSM; it consists of

different processors, in BSNL it is of SUN Polaris of LG Company. In LG 1 BSC can have 48 BTS? In

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BSNL we have two types of BSC:-

I. V-5.2:- This type of BSC cannot switch by itself so it is dependent on local exchange /

PSTN for switching and keeping records of billing etc. BSNL uses this type of BSC for rural areas.

ii. CCS-7 / R2:- These types of BSC are totally automatic it doesn’t depend on local

exchange for its functions, it is complete in itself. BSNL uses this type of BSC for urban areas.

BTS (Base Transreceiver System):- As it is clear from its name it transmits as well as receive

signal, it works as an amplifier (router) to overcome the loss in signal in transmission.

BSM (Base Station Management):- It controls and manages the WLL services. It can

troubleshoot the problem; add new users as well as capable to block service given to user. It is

basically a computer system, which manages the whole process of WLL service. In BSNL BSM are

two UNIX based computer system.

ADVANTAGES OF WLL:

Country wide induction of WLL underway of areas than are non-feasible for the normal

network

Helping relieves congestion of connections in the normal cable / wire based network in urban

areas

Limited the mobility without any airtime charges

It has improved signal and reducing the interference

Greater capacity than mobile

Provides ease of operation, administration & maintenance at lower cost.

The telecommunication is the biggest factor in influencing the speed of life in the modern age.

Today we can get connection with any corner of world through the push button of computer;

with the small mobile phone we can send not only the messages but also the secret document.

As we know that there is positive view behind any mention that it should be helpful in the

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development of society. But humans have diverted mentality some of them of positive view and

some of them of negative view. Where use any invention for the welfare of society but some

uses for the satisfaction their disturbed mentality and to earn more and more money whether it

may be harmful for the society. They infringe the norms of society and their behavior is

condemned as antisocial, immoral and sinful.

2. CODE DIVISION MULTIPLE ACCESS (CDMA):

CONCEPT OF MULTIPLE ACCESSES: -

Multiple access system allows a large number of users to share a common pool of radio

telephone circuits, like sharing of trunked radio facility. Multiple access radio has similarity to

the LAN in which the common channel is available to all users. The circuits are demands

assigned i.e. assigned on demand first-cum-first-served basis. The provision of access to the

radio circuits methods of multiple accesses are:

CDMA: - Where large number of transmission are combined on the same channel at the same

time and separated by the codes.

WHAT IS CDMA?

CDMA, a cellular technology originally known as IS-95, competes with GSM technology for

dominance in the cellular world.

There are now different variations, but the original CDMA is known as CdmaOne.

Latest CDMA global subscriber & operator’s numbers

As of December 2002, there were 120 million users worldwide, with 55 million of these in the

USA.

See other cellular technology in the world.

We now have CDMA2000 and its variant like 1X EV, 1XEV-DO and MC 3X. The refer of variant of

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usage of a 1.25 MHz channel. 3X uses a 5 MHz channel. Wide band CDMA forms that the basis of

UMTS 3G networks, developed originally by Qualcomm, high capacity and small cell radius,

employing spread-spectrum technology and special coding scheme characterized by CDMA.

The Telecommunication Industry Association (TIA) in 1993 adopted CDMA. May 2001 there

were 35 million subscribers on cdmaOne system worldwide. Over 35 countries have either

commercial or trial activity ongoing. There were already 43 WLL systems in 22 countries using

cdmaOne technology.

Enhancing today’s data capabilities is the 1XRTT CDMA standard this next evolutionary step for

cdmaOne operators will provide data rates up to 300 kbps, significant capacity increases as well

as extended batteries life for handsets.

Worldwide resources are being devoted to roll out third generation CDMA technology, including

multi-carrier (cdmaOne2000 1xMC and HDR in 1.25 MHz bandwidth and 3xMC in 5 MHz

bandwidth) and direct spread (WCDMA in 5 MHz bandwidth).

This first phase of cdmaOne2000 variously called 1XRTT, 3G1X or just plain 1X is designed to

double current voce capacity and support always on data transmission speed 10 times faster

than typically available today, some 153.6 kbps on both the forward and reverse links.

3. GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM): -

The GSM Association is a unique organization, with a truly global reach, offering a full

range of business and technical services to its members. Now as the wireless family unfolds the

association is deriving forward its vision of seamless, limitless, world of wireless communication.

Throughout the evolution of cellular telecommunications, various systems have been developed

without the benefit of standardized specifications. This presented many problems directly

related to compatibility, especially with the development of digital radio technology. The GSM

standard is intended to address these problems.

Global system for mobile communication (GSM) is a globally accepted standard for digital

cellular communication. GSM is the name of a standardization group established in 1982 to

create a common European mobile telephone standard that would formulae the specifications

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for a pan-European mobile cellular radio system operating at 900 MHz it is estimated that many

countries outside of Europe will join the GSM partnership.

OBJECTIVES OF GSM SYSTEM:

One of the important objectives of GSM group is to evolve a unified standard to provide seamless roaming across Europe. Another landmark decision taken by the group is to standardize a digital radio interface for the communication between the mobile handset and the radio transmitter / receiver. The design objectives of the GSM system can be briefly states as below:

Excellent speech quality High security and privacy Low module terminal cost Low service and facilities cost Design of sleek and handled mobile terminals International roaming Wide range of services and facilities Ability to adopt to new and innovative features Narrowband ISDN compatibility Digital Radio High Spectral efficiency

GSM NETWORK ELEMENTS AND ARCHITECTURE:

1. Mobile Station (MS) i. Mobile Terminal or Equipment (MT)

ii. Subscriber Identity Module (SIM) Card

2. Base Station Subsystem (BSS) i. Base transceiver Station (BTS)

ii. Base Station Controller (BSC) iii. Main Station Controller (MSC)iv. Transcoding and Rate Adoption Unit (XCDR/TRAU)

3. Network Switching Subsystem (NSS) i. Registration

ii. Authentication and security iii. Location updating iv. Handovers and

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v. Routing to roaming subscribers

4. Operation and Maintenance Subsystem (OMS) i. Operation and Maintenance Centre – Switch

ii. Operation and Maintenance Centre – Radio

5. Enhanced Services Subsystem (ESS)

6. Billing and Customer Care System (B&CCS)

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4. THIRD GENERATION 3G TECHNOLOGY : -

Introduction: -

Third generation (3G) networks were conceived from the Universal Mobile Telecommunications Service (UMTS) concept for high speed networks for enabling a variety of data intensive applications. 3G systems consist of the two main standards, CDMA2000 and W-CDMA, as well as other 3G variants such as NTT DoCoMo's Freedom of Mobile Multimedia Access (FOMA) and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) used primarily in China.

Data Speed

The data speed of 3G is determined based on a combination of factors including the chip rate, channel structure, power control, and synchronization.

An example of calculating the theoretical 3G data speed is as follows:

W-CDMA assigned code 400-500 Kbps/code. 6 codes X 400 > 2Mbps (UMTS target for 3G data speed in fixed location)

Actual data speeds will vary in accordance with several factors including:

Number of users in cell/sector Distance of user from cell User is moving or stationary Network operator capacity and network optimization requirements

1xEV-DO is a data-only solution, supporting a theoretical data speed of up to 2.457 Mbps

1xEV-DV is a data and voice solution, supporting a theoretical data speed of up to 3.072 Mbps

FOMA has two operational modes, supporting a dedicated 64 Kbps connection or a 384 Kbps downlink/64 Kbps uplink best-effort connection.

TD-SCDMA can operate in 1.6 MHz or 5 MHz mode for 2 Mbps or 6 Mbps respectively

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3G is the short form for third-generation technology. It is one of the popular mobile phone standards. The services utilizing 3G provide the ability to transmit both voice data such as calls and non-voice data such as instant messaging, email and video telephony at the same time. Japan was the first country to introduce 3G on a wide scale commercially. In 2005, almost 40 per cent of the subscribers in Japan used 3G services. On the technical front, 3G services are wide area cellular telephone networks unlike IEEE 802.11 networks, which are short range networks meant for Internet access. Now, 3G is being used to provide various services.

You have to plug in 3G Data Card into your laptop and can get the fastest available connection, with mobile broadband speeds of up to 1.8 Mbps. It’s neat, compact design makes it easy to use; you can easily swap it between laptops for use at work, home or on the move. Laptops have a PC Card slot (also known as a PCMCIA slot), or an Express Card slot. There is PCMCIA to Express Card Converter for using 3G broadband; you need 3G Data card, network SIM card, software, user guide.

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History of Wireless

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BSNL’s IPTV

• First started in Japan in 2002.

• Popular in France, South Korea, Germany, Hongkong etc.

• France is leading in IPTV having more than 1.7 million IPTV viewers

Global IPTV subscriber’s base will reach 14.5 million in 2007 and will be approximately 63 million by 2010.

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CONCLUSION: -

Hence in the last I can say that taking training in such an organization proved to be very beneficial for me. I learnt quite a lot about electronic exchange, Internet, Land line, WLL, Mobile GSM & 3G, and the basis of processing Exchange. I also got firsthand knowledge of how a Telephone Exchange works.

The first phase of training has proved to be quite fruitful. It provides an opportunity to encounter with such huge machines.

The architecture of company has various units. They are linked and working of whole plant is controlled make the student realized that engineering is not just learning the structure description and working of various machines. But the greater part is planning proper management.

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GLOSSARY OF TERMS AND ABBREVIATIONS

ADM Add/Drop Multiplexers

ANALOGUE An electrical signal which is analogous to changing physical quantity measured

BSC Base Station Controller

BTS Base Tran receiver Station

C-DOT Centre for Development of Telemetric

CD Cabinet Cable Distribution Cabinet

CDMA Code Division Multiple Access

CKM Cable conductor kilometer – cable sheath kilometers multiplied by the number of conductor pairs in each cable

CLIP Calling Line Identification Processing

COAXIAL CABLE A cable with a single wire in the centre of cylindrical conductor forming a pair of carrying electrical signals

CT BOXES Cable Termination Boxes

DECT Digital Enhanced Cordless Telecommunications

DEL Direct exchange lines, one each for every telephone connection

DIGITAL EXCHANGE The exchange having signals coded into binary pulses and having little or no moving parts

DIU DECT interface unit

DLC Digital Loop Carrier

DWDM Dense Wavelength Multiplexing Terminal

EDX Electronic Data Exchange

EPABX Electronic Private Automatic Branch Exchange

ETRP Electronic Trunk Relay Plates

EWSD TAX Electronic Wheeler System of Digital Trunk Automatic Exchange

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GHz Giga Hertz

GSM Global System for Mobile Communications

HDPE High density polyethylene

HDSL High bit rate Digital Subscriber Line

Hertz or Hz Frequency (cycles per second), named after Heinrich Hertz - usually in ranges of kilo 1000 - KHz, mega 1,000,000 - MHz or giga 1,000,000,000 - GHz

IDR Intermediate Data Rate

ISDN Integrated Services Digital Network

LDST Long Distance Satellite Telephone

LOI Letter of Intent

MARR Multi Access Rural Radio

MBM Multi Base Module

Mbps Mega bits per second denoting digital frequency

MCPC Multi Channel Per Carrier

MDF Main Distribution Frame

MUX Multiplex

NIT Notice Inviting Tender

NE Lines Non Exchange Lines

OFC Optical Fiber Cable

Optical Fiber (OF) Glass fibers using light waves for transmission of signals

OLA Optical Line Amplifiers

OYT Own your telephone

PABX Private Automatic Branch exchange

PBX Private branch exchange

PCM Pulse Code Modulation

PCO Public Call Offices

PDH Plesiochronous Digital Hierarchy

PERT Chart Programmed Evaluation Review Technique Chart

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PIJF Cable Polyethylene Insulated Jelly Filled Cable

PSPDN Packet Switch Public Data Network

PST Progressive Stock Taking

PSTN Public Switched Telephone Network

PVC Polyvinyl chloride

PW Private Wires

RLU Remote Line Unit

RSU Remote Switching Unit

SACFA Standing Advisory Committee on Radio Frequency Allocation

SDH Synchronous Digital Hierarchy

SMPS Switch Mode Power Supply

SRCs Subscriber Record Cards

SSAs Secondary Switching Areas

STD Subscriber trunk dialing

STM Synchronous Transport Module

TAX Trunk automatic exchange

TDMA Time Division Multiple Access – A transmission technique used in digital radio transmission in which the use of a frequency is divided into time slots that are shared amongst several users.

TELEX TelePrompTer exchange

TTH Triangular Tubular Hybrid

UHF Ultra high frequency (300 to 3000 MHz)

VHF Very high frequency

VPT Village Public Telephones

VSAT Very small aperture terminal

WLL Wireless-in-Local Loop

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Sumit's BSNL Training Report

Documents

days of training

bsnl training report

training period

aware of practical knowledge

theoretical knowledge

practical training course

kota raj

field of communication