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REPORT ON

SIGNAL AND TELECOMMUNICATION

SIGNAL & TELECOMMUNICATION

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PREFACE

In its broadest sense summer training is necessary to make the students familiar with theindustrial environment prevailing in the world. To be competitive students need to knowthe policies, procedures and the trends going on in the present industrial world.

In every professional course, training is an important factor. Professors give ustheoretical knowledge of various subjects in the college but we are practically exposed ofsuch subjects when we get the training in the organization. It is only the training throughwhich I come to know that what an industry is and how it works. I can learn aboutvarious departmental operations being performed in the industry, which would, in return,

help me in the future when I will enter the practical field.

Training is an integral part of B.TECH and each and every student has to undergo thetraining for 1 month in a company and then prepare a project report on the same after thecompletion of training.

During this whole training I got lot of experience and came to know about variouscommunication techniques and other practices in real that how it differs from those oftheoretical knowledge and the practically in the real life.

In todays globalize world, where cutthroat competition is prevailing in the market,

theoretical knowledge is not sufficient. Beside this one need to have practicalknowledge, which would help an individual in his/her carrier activities and it is true thatExperience is the best teacher.

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ACKNOWLEDGEMENT

Indian Railway (South Eastern Railway) being a strategic organization requires strict and

effective administration in it works. SIGNAL & TELE-COMMUNICATION department

take care of proper functioning of communication and in turn plays a crucial role in

safety of passengers traveling every day.

I am really very thankful of proper guidance of Mr. B. K. PAL (SSE/TEL.EX) and Mr.

Y.C.SINGH (SSE/TEL. CNTRL) in helping out me to overcome many crucial problems

which I face as a trainee and thanking all the staff for proper guidance and instruction. I

am thankful to Sr. DSTE, DSTE for their support and cooperation.

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CONTENTS

1. INTRODUCTION

2. COMMUNICATION

3. OPTICAL FIBER CABLE

4. EXCHANGE - ISDN

5. SDH SYSTEM

6. PRS AND UTS

7. CONTROL

8. ABBREVIATIONS

9. CONCLUSION

10. REFERENCES

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INTRODUCTION

HISTORY:

The first railway on Indian sub-continent ran over a stretch of 21 miles from Bombay toThane.

The idea of a railway to connect Bombay withThane, Kalyan and with the Thal and Bhore Ghatsinclines first occurred to Mr. George Clark, theChief Engineer of the Bombay Government, during

a visit to Bhandup in 1843.

The formal inauguration ceremony was performedon 16th April 1853, when 14 railway carriagescarrying about 400 guests left Bori Bunder at 3.30pm "amidst the loud applause of a vast multitude and to the salute of 21 guns."

The first passenger train steamed out of Howrahstation destined for Hooghly, a distance of 24miles, on 15th August, 1854. Thus the firstsection of the East Indian Railway was opened topublic traffic, inaugurating the beginning of

railway transport on the Eastern side of the sub-continent.

In south the first line was opened on 1st July,1856 by the Madras Railway Company. It ranbetween Veyasarpandy and Walajah Road

(Arcot), a distance of 63 miles. In the North a length of 119 miles of line was laid fromAllahabad to Kanpur on 3rd March 1859. The first section from Hathras Road to MathuraCantonment was opened to traffic on 19th October, 1875.

These were the small beginnings which is due course developed into a network of railway

lines all over the country. By 1880 the Indian Railway system had a route mileage ofabout 9000 miles.

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STRUCTURE

Indian Railways has one of the largest and busiest rail networks in the world, transportingover 18 million passengers and more than 2 million tones of freight daily. It is the world'slargest commercial or utility employer, with more than 1.4 million employees. Therailways traverse the length and breadth of the country, covering 6,909 stations over atotal route length of more than 63,327 kilometers (39,350 mi). As to rolling stock, IRowns over 200,000 (freight) wagons, 50,000 coaches and 8,000 locomotives. IndianRailways operates about 9,000 passenger trains and transports 18 million passengersdaily across twenty-eight states and one union territory. Sikkim, Arunachal Pradesh andMeghalaya are the only states not connected by rail. The passenger division is the mostpreferred form of long distance transport in most of the country.

Indian Railways is divided into zones, which are further sub-divided into divisions. The

number of zones in Indian Railways increased from six to eight in 1951, nine in 1952,and finally 16 in 2003. Each zonal railway is made up of a certain number of divisions,each having a divisional headquarters. There are a total of sixty-seven divisions.

Each of the sixteen zones, as well as the Kolkata Metro, is headed by a General Manager(GM) who reports directly to the Railway Board. The zones are further divided intodivisions under the control of Divisional Railway Managers (DRM). The divisionalofficers of engineering, mechanical, electrical, signal & telecommunication, accounts,personnel, operating, commercial and safety branches report to the respective DivisionalManager and are in charge of operation and maintenance of assets. Further down thehierarchy tree are the Station Masters who control individual stations and the train

movement through the track territory under their stations' administration. (See fig.)

6

RAILWAY BOARD

ZONAL RAILWAYS(16 ZONES)

DIVISIONS

ENGG.

OPERATING PERSONNEL ACCOUNTS SAFETY

MECH ELECT S & T COMM

DIVISION OF RAILWAY BOARD

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COMMUNICATION

Today, it would be difficult for us to imagine life without the telephone. World-wide,

there are some 750 million telephone connections in use and the number of Internet usershas exploded in the last few years. By the year 2010, according to a forecast from Nortel,there will be almost 475 million Internet users and the number of services provided willalso grow rapidly.

To control the working of employers and to ensure the proper running of trains, we needfast and reliable means of communication. To ensure this we have SIGNAL &TELECOMMUNICATION department. They provide path and sources (Equipments)to communicate. Their work is to provide the line and maintain it.

Railway communication provides uninterrupted motion of trains. Due to faster means of

communication there is increase in the efficiency and greater control. To communicatewe require some media, which carry our signal. In past, railway use iron wires, copperwires or aluminum wires for signal propagation. Now, a day we railway use Microwave,Quad cable, Optical Fiber cable & satellite communication.

The explosion in demand for network bandwidth is largely due to the growth in datatraffic, specifically Internet Protocol (IP). Leading service providers report bandwidthsdoubling on their backbones about every six to nine months. This is largely in response tothe 300 percent growth per year in Internet traffic, while traditional voice traffic grows ata compound annual rate of only about 13 percent.

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OPTICAL FIBRE CABLE

Optical fiber is generally made of glass & is made into very thin fibers or hair size. It is a non-metallic conductor that can transmit light energy from one end to the other end by utilizing the

phenomena of Total Internal reflection of light. In conventional cables (copper cables)electrical energy is transmitted through metallic conductors. An optical fiber communicationsystem consists of transmitter, which converts the multiplexed electrical signal into an opticalsignal. A source of light launches the optical signal through a coupler into the fiber. The fibercarries this signal to the receiver, where another coupler couples the light from the fiber to thedetector. The transmitter uses either a LASER DIODE or LIGH EMITTED DIODE (LED) forelectrical to optical conversion. The receiver uses either a PIN diode or an AVALANCHEDIODE (APD) for electrical conversion.

GROWTH OF OPTICAL FIBER

How Fiber Works:

The main job of optical fibers is to guide light waves with a minimum of attenuation (lossof signal).Optical fibers are composed of fine threads of glass in layers, called the coreand cladding, which can transmit light at about two-thirds the speed of light in a vacuum.Though admittedly an oversimplification, the transmission of light in optical fiber iscommonly explained using the principle of TOTAL INTERNAL REFLECTION. Withthis phenomenon, 100 percent of light that strikes a surface is reflected.By contrast, a mirror reflects about 90 percent of the light that strikes it.

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Light is either reflected (it bounces back) or refracted (its angle is altered while passingthrough a different medium) depending upon the angle of incidence (the angle at whichlight strikes the interface between an optically denser and optically thinner material).Total internal reflection happens when the following conditions are met: Beams pass from a denser to a less dense material. The difference between the optical

density of a given material and a vacuum is the materials refractive index.2-6

Optical Fibers:

The incident angle is less than the critical angle. The critical angle is the maximum angleof incidence at which light stops being refracted and is instead totally reflected.The principle of total internal reflection within a fiber core is illustrated in Figure. Thecore has a higher refractive index than the cladding, allowing the beam that strikes thatsurface at less than the critical angle to be reflected. The second beam does not meet thecritical angle requirement and is refracted.

Principle of Total Internal Reflection

An optical fiber consists of two different types of highly pure, solid glass (silica)thecore and the claddingthat are mixed with specific elements, called dopants, to adjusttheir refractive indices. The difference between the refractive indices of the two materialscauses most of the transmitted light to bounce off the cladding and stay within the core.The critical angle requirement is met by controlling the angle at which the light isinjected into the fiber. Two or more layers of protective coating around the claddingensure that the glass can be handled without damage.

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TYPE OF OPTICAL FIBERS

Multimode and Single-Mode Fiber:

There are two general categories of optical fiber in use today, multimode fiber and single-mode fiber.Multimode, the first type of fiber to be commercialized, has a larger core than single-mode fiber. It gets its name from the fact that numerous modes, or light rays, can becarried simultaneously through the waveguide. Figure shows an example of lighttransmitted in the first type of multimode fiber, called step-index. Step-index refers to thefact that there is a uniform index of refraction throughout the core;Thus there is a step in the refractive index where the core and cladding interface. Noticethat the two modes must travel different distances to arrive at their destinations. Thisdisparity between the times that the light rays arrive is called modal dispersion. Thisphenomenon results in poor signal quality at the receiving end and ultimately limits thetransmission distance. This is why multimode fiber is not used in wide-area applications.To compensate for the dispersion drawback of step-index multimode fiber, graded-indexfiber was invented. Graded-index refers to the fact that the refractive index of the core isgradedit gradually decreases from the center of the core

Reflected Light in Step-Index Multimode Fiber

Outward. The higher refraction at the center of the core slows the speed of some lightrays, allowing all the rays to reach their destination at about the same time and reducingmodal dispersion.

Reflected Light in Single-Mode Fiber

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The second general type of fiber, single-mode, has a much smaller core that allows onlyone mode of light at a time through the core. As a result, the fidelity of the signal is betterretained over longer distances, and modal dispersion is greatly reduced. These factorsattribute to a higher bandwidth capacity than multimode fibers are capable of. For itslarge information-carrying capacity and low intrinsic loss, single-mode fibers are

preferred for longer distance and higher bandwidth applications, including DWDM.

DWDM SYSTEM FUNCTION

The system performs the following main functions: Generating the signalthe source, a solid-state laser, must provide stable light within a

specific, narrow bandwidth that carries the digital data, modulated as an analog signal. Combining the signalsModern DWDM systems employ multiplexers to combine thesignals. There is some inherent loss associated with multiplexing and demultiplexing.This loss is dependent upon the number of channels but can be mitigated with opticalamplifiers, which boost all the wavelengths at once without electrical conversion. Transmitting the signalsthe effects of crosstalk and optical signal degradation or lossmust be reckoned with in fiber optic transmission. These effects can be minimized bycontrolling variables such as channel spacing, wavelength tolerance, and laser powerlevels. Over a transmission link,The signal may need to be optically amplified. Separating the received signalsat the receiving end, the multiplexed signals must be

separated out. Although this task would appear to be simply the opposite of combiningthe signals, it is actually more technically difficult. Receiving the signalsthe demultiplexed signal is received by a photo detector. Inaddition to these functions, a DWDM system must also be equipped with client-sideinterfaces to receive the input signal. This function is performed by transponders. On theDWDM side are interfaces to the optical fiber that links DWDM systems.

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Options for Increasing Carrier Bandwidth

Faced with the challenge of dramatically increasing capacity while constraining costs,

carriers have two options: Install new fiber or increase the effective bandwidth of existingfiber.

Laying new fiber is the traditional means used by carriers to expand their networks.Deploying new fiber, however, is a costly proposition. It is estimated at about $70,000per mile, most of which is the cost of permits and construction rather than the fiber itself.Laying new fiber may make sense only when it is desirable to expand the embedded base.

Increasing the effective capacity of existing fiber can be accomplished in two ways: Increase the bit rate of existing systems. Increase the number of wavelengths on a fiber.

Increase the Bit Rate:

Using TDM, data is now routinely transmitted at 2.5 Gbps (OC-48) and, increasingly, at10 Gbps(OC-192); recent advances have resulted in speeds of 40 Gbps (OC-768). Theelectronic circuitry that makes this possible, however, is complex and costly, both topurchase and to maintain. In addition, there are significant technical issues that mayrestrict the applicability of this approach. Transmission at OC-192 over single-mode(SM) fiber, for example, is 16 times more affected by chromatic dispersion than the next

lower aggregate speed, OC-48. The greater transmission power required by the higher bitrates also introduces nonlinear effects that can affect waveform quality. Finally,polarization mode dispersion, another effect that limits the distance a light pulse cantravel without degradation, is also an issue. These characteristics of light in fiber arediscussed further in the Optical Fibers.

Increase the Number of Wavelengths:

In this approach, many wavelengths are combined onto a single fiber. Using wavelengthdivision multiplexing (WDM) technology several wavelengths, or light colors, cansimultaneously multiplex signals of 2.5 to 40 Gbps each over a strand of fiber. Without

having to lay new fiber, the effective capacity of existing fiber plant can routinely beincreased by a factor of 16 or 32. Systems with 128 and 160 wavelengths are in operationtoday, with higher density on the horizon. The specific limits of this technology are notyet known.

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EXCHANGE

I S D N:

ISDN stands for integrated services Digital network was introduced in 1979.

Integrated Services Digital Network (ISDN) is a set of communications standards for

simultaneous digital transmission of voice, video, data, and other network services over

the traditional circuits of the public switched telephone network. It was first defined in

1988 in the CCITT red book.

An ISDN is a network, in general evolving from a telephone IDN that provides end to

end digital connectivity to support a wide range of services, to which users have access

by a limited set of standard multipurpose user network interfaces.

Network It is a communication carrying system including medium, switching points

and proper routing. Networks follow certain protocols for transmission.

Digital The communication is digital up to subscribers instrument. But it is also

compatible to analog working instruments, though the transmission is in digital mode.

Services Services to the subscriber like transmission of speech, image and data.

Integrated - All the three services are transmitted simultaneously on a single pair of

wires.

Speech: 64 kbps.

Image 64 kbps (minimum.)

Data 16 kbps

The transmission is possible on the existing copper wire pairs. Even though replacing the

copper wire with fiber is more ideal, the copper cable network, which is already existing

need not be immediately replaced as very high amounts of expenditure is to be incurred

at once which is unnecessary. The existing copper network can be made use upto

5.1 km 0.5 mm gauge copper conductor cable

4.0 km 0.4 mm gauge copper conductor cable

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http://en.wikipedia.org/wiki/Digitalhttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Public_switched_telephone_networkhttp://en.wikipedia.org/wiki/CCITThttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Public_switched_telephone_networkhttp://en.wikipedia.org/wiki/CCITThttp://en.wikipedia.org/wiki/Digital

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ISDN is intended to be a worldwide public telecommunications network to replace the

existing telecommunications networks and deliver a wide variety of services. The ISDN

is defined by the standardization of user interfaces and will be implemented as a set of

digital switches and paths supporting a broad range of traffic types and providing value

added processing services. In, practice there will be multiple networks, implemented

within the national boundaries, but from the users point of view, there will be a single,

uniformly accessible, worldwide network.

ISDN has emerged as a powerful tool for provision of voice, data and image by means of

existing network.

There are two basic types of ISDN service: Basic Rate Interface (BRI) and Primary Rate

Interface (PRI). BRI consists of two 64 kb/s B channels and one 16 kb/s D channel for a

total of 144 kb/s. This basic service is intended to meet the needs of most individual

users.

PRI is intended for users with greater capacity requirements. Typically the channel

structure is 23 B channels plus one 64 kb/s D channel for a total of 1536 kb/s. In Europe,

PRI consists of 30 B channels plus one 64 kb/s D channel for a total of 1984 kb/s. It is

also possible to support multiple PRI lines with one 64 kb/s D channel using Non-Facility

Associated Signaling (NFAS).

H channels provide a way to aggregate B channels. They are implemented as:

H0=384 kb/s (6 B channels)

H10=1472 kb/s (23 B channels)

H11=1536 kb/s (24 B channels)

H12=1920 kb/s (30 B channels) - International (E1) only

To access BRI service, it is necessary to subscribe to an ISDN phone line. Customer must

be within 18000 feet (about 3.4 miles or 5.5 km) of the telephone company central office

for BRI service; beyond that, expensive repeater devices are required, or ISDN service

may not be available at all. Customers will also need special equipment to communicate

with the phone company switch and with other ISDN devices. These devices include

ISDN Terminal Adapters (sometimes called, incorrectly, "ISDN Modems") and ISDN

Routers.

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The early phone network consisted of a pure analog system that connected telephone

users directly by a mechanical interconnection of wires. This system was very inefficient,

was very prone to breakdown and noise, and did not lend itself easily to long-distance

connections. Beginning in the 1960s, the telephone system gradually began converting its

internal connections to a packet-based, digital switching system. Today, nearly all voice

switching in the U.S. is digital within the telephone network. Still, the final connection

from the local central office to the customer equipment was, and still largely is, an analog

Plain-Old Telephone Service (POTS) line.

Most recently, ISDN service has largely been displaced by broadband internet service,

such as xDSL and Cable Modem service. These services are faster, less expensive, and

easier to set up and maintain than ISDN. Still, ISDN has its place, as backup to dedicated

lines, and in locations where broadband service is not yet available

Speed:

The modem was a big breakthrough in computer communications. It allowed computers

to communicate by converting their digital information into an analog signal to travel

through the public phone network. There is an upper limit to the amount of information

that an analog telephone line can hold. Currently, it is about 56 kb/s bidirectional.

Commonly available modems have a maximum speed of56 kb/s, but are limited by the

quality of the analog connection and routinely go about 45-50 kb/s. Some phone lines do

not support 56 kb/s connections at all.

Multiple Devices:

Previously, it was necessary to have a separate phone line for each device you wished to

use simultaneously. For example, one line each was required for a telephone, fax,

computer, bridge/router, and live video conference system. Transferring a file to someone

while talking on the phone or seeing their live picture on a video screen would require

several potentially expensive phone lines. ISDN allows multiple devices to share a single

line. It is possible to combine many different digital data sources and have the

information routed to the proper destination. Since the line is digital, it is easier to keep

the noise and interference out while combining these signals. ISDN technically refers to a

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specific set of digital services provided through a single, standard interface. Without

ISDN, distinct interfaces are required instead.

Signaling:

Instead of the phone company sending a ring voltage signal to ring the bell in your phone

("In-Band signal"), it sends a digital packet on a separate channel ("Out-of-Band signal").

The Out-of-Band signal does not disturb established connections, no bandwidth is taken

from the data channels, and call setup time is very fast. For example, a V.90 or V.92

modem typically takes 30-60 seconds to establish a connection; an ISDN call setup

usually takes less than 2 seconds. The signaling also indicates who is calling, what type

of call it is (data/voice), and what number was dialed. Available ISDN phone equipment

is then capable of making intelligent decisions on how to direct the call.

ADVANTAGES OF ISDN

High speed and high quality communication

Reliability and security.

Better use of existing facility

International standardization

Simplified wiring

Efficiency of network usage

Standard data transport rate

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SDH SYSTEM

SDH (Synchronous Digital Hierarchy) is a standard for telecommunications transport

formulated by the International Telecommunication Union (ITU), previously called theInternational Telegraph and Telephone Consultative Committee (CCITT). SDH was firstintroduced into the telecommunications network in 1992 and has been deployed at rapidrates since then. Its deployed at all levels of the network infrastructure, including theaccess network and the long-distance trunk network. Its based on overlaying asynchronous multiplexed signal onto a light stream transmitted over fiber-optic cable.SDH is also defined for use on radio relay links, satellite links, and at electrical interfacesbetween equipment. The comprehensive SDH standard is expected to provide thetransport infrastructure for worldwide telecommunications for at least the next two orthree decades. The increased configuration flexibility and bandwidth availability of SDHprovides significant advantages over the older telecommunications system. These

advantages include: A reduction in the amount of equipment and an increase in network reliability. The provision of overhead and payload bytes the overhead bytes permittingmanagement of the payload bytes on an individual basis and facilitating centralized faultsection. The definition of a synchronous multiplexing format for carrying lower-level digitalsignals (such as 2 Mbit/s, 34 Mbit/s, 140 Mbit/s) which greatly simplifies the interface todigital switches, digital cross-connects, and add/drop multiplexers. The availability of a set of generic standards, which enable multi-vendorinteroperability. The definition of a flexible architecture capable of accommodating future applications,with a variety of transmission rates. In brief, SDH defines synchronous transport modules(STMs) for the fiber-optic based transmission hierarchy.

Synchronization Hierarchy:

Digital switches and digital cross-connect systems are commonly employed in the digitalnetwork synchronization hierarchy. The network is organized with a master-slaverelationship with clocks of the higher-level nodes feeding timing signals to clocks of thelower-level nodes. All nodes can be traced up to a Primary Reference Clock (PRC).

Synchronizing SDH:

The internal clock of an SDH terminal may derive its timing signal from aSynchronization Supply Unit (SSU) used by switching systems and other equipment.Thus, this terminal can serve as a master for other SDH nodes, providing timing on itsoutgoing STM-N signal. Other SDH nodes will operate in a slave mode with theirinternal clocks timed by the incoming STM-N signal. Present standards specify that anSDH network must ultimately be able to derive its timing from a PRC.

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STM-1 FRAME STRUCTURE

Virtual container structure showing VC-4

SDH Network Configurations:

Point-to-Point:-

The simplest network configuration involves two terminal multiplexers linked byfibre with or without a regenerator in the link (sees Figure). In this configuration, theSDH path and the Service path (for example, E1 or E3 links end to-end) are identical and

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this synchronous island can exist within an asynchronous network world. In the future,point-to-point service path connections will span across the whole network and willalways originate and terminate in a multiplexer.

Point-to-Multipoint:-

A point-to-multipoint (linear add/drop) architecture includes adding and dropping circuitsalong the way (see Figure). The SDH ADM (add/drop multiplexer) is a unique networkelement specifically designed for this task. It avoids the current cumbersome network

architecture of demultiplexing, cross-connecting, adding and dropping channels, and thenre-multiplexing. The ADM typically is placed in an SDH link to facilitate adding anddropping tributary channel sat intermediate points in the network.

Mesh Architecture:-

The meshed network architecture accommodates unexpected growth and change more

easily than simple point-to-point networks. A cross-connects function concentrates trafficat a central site and allows easy re-provisioning of the circuits (see Figure). There are twopossible implementations of this type of network function:1. Cross-connection at higher-order path levels, for example, using AU-4 granularity inthe switching matrix.2. Cross-connection at lower order path levels, for example, using TU-12 granularity inthe switching matrix.

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Ring Architecture:-

The SDH building block for ring architecture is the ADM (see Figure). Multiple ADMscan be put into a ring configuration for either Bidirectional or Uni-directional traffic. Themain advantage of the ring topology is its survivability; if a fiber cable is cut, forexample, the multiplexers have the local intelligence to send the services affected via analternate path through the ring without a lengthy interruption.The demand for survivable services, diverse routing of fiber facilities, flexibility torearrange services to alternate serving nodes, as well as automatic restoration withinseconds, have made rings a popular SDH topology.

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Benefits of SDH Conclusions

A transport network using SDH provides much more powerful networking capabilitiesthan existing asynchronous systems. The key benefits provided by SDH are thefollowing.

Pointers, MUX/DEMUX:-As a result of SDH transmission, the network clocks are referenced to a highly stablereference point; so the need to align the data streams using non-deterministic bit-stuffingis unnecessary. Therefore, a lower rate channel such as E1 is directly accessible, andintermediate demultiplexing is not needed to access the bit streams.For those situations in which synchronisation reference frequency and phase may vary,SDH uses pointers to allow the streams to float within the payload. Pointers are the keyto synchronous timing; they allow a very flexible allocation and alignment of the payloadwithin the transmission frame.

Reduced Back-to-Back Multiplexing:-In the asynchronous PDH systems, care must be taken when routing circuits in order toavoid multiplexing and demultiplexing too many times since electronics (and theirassociated capital cost) are required every time an E1 signal is processed. With SDH, E1scan be multiplexed directly to the STM-N rate. Because of synchronisation, an entireoptical signal doesnt have to be demultiplexed only the individual VC or STM signalsthat need to be accessed.

Optical Interconnect:-A major SDH benefit is that it allows mid-span meet with multi-vendor compatibility.Todays SDH standards contain definitions for fibre-to-fibre interfaces at the physicallevel. They determine the optical line rate, wavelength, power levels, pulse shapes, andcoding. The current standards also fully define the frame structure, overhead, and payloadmappings.Enhancements are being developed to define the messages in the overhead channels toprovide increased OAM functionality.SDH allows optical interconnection betweennetwork providers regardless of who makes the equipment. The network provider canpurchase one vendors equipment and conveniently interface with other vendors SDHequipment at either operator locations or customer premises. Users may now obtain theSTM-N equipment of their choice and meet with their network provider of choice at thatSTM-N level.

Multi-point Configurations:-Most existing asynchronous transmission systems are only economic for point-to-pointapplications, whereas SDH can efficiently support a multi-point or cross-connectedconfiguration.

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The cross-connect allows many nodes or sites to communicate as a single networkinstead of as separate systems. Cross-connecting reduces requirements for back-to-backmultiplexing and demultiplexing, and helps realize the benefits of traffic grooming.Network providers no longer need to own and maintain customer-located equipment. Amulti-point implementation permits STM-N interconnects and mid-span meets, allowing

network providers and their customers to optimize their shared use of the SDHinfrastructure.

Grooming:-

Grooming refers to either consolidating or segregating traffic to make more efficient useof the network facilities. Consolidation means combining traffic from different locationsonto one facility, while segregation is the separation of traffic.Grooming eliminates inefficient techniques such as back-hauling. Its possible to groomtraffic on asynchronous systems, however to do so requires expensive back-to-backconfigurations and manual or electronic cross-connects. By contrast, an SDH system can

segregate traffic at either an STM-1 or VC level to send it to the appropriate nodes.Grooming can also provide segregation of services. For example, at an interconnectpoint, an incoming SDH line may contain different types of traffic, such as switchedvoice, leased circuits for data, or video. An SDH network can conveniently segregate theswitched and non-switched traffic.

Enhanced OAM:-

SDH allows integrated network OAM, in accordance with the philosophy of single-endedmaintenance. In other words, one connection can reach all network elements within a

given architecture; separate links are not required for each network element. Remoteprovisioning provides centralized maintenance and reduced travel for maintenancepersonnel which translate to expense savings.

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UTS AND PRS

In 1982, Government set up Freight Operations information Systems (FOIS) for freightoperations computerization on Indian Railways, later in 1986, Ministry of Railwaysestablished CENTRE FOR RAILWAY INFORMATION SYSTEMS (CRIS) anumbrella for all computer activities on Indian Railways (IR). They also entrusted it withthe task of design, development and implementation of the FOIS, along with itsassociated communications infrastructure. The Centre started functioning from July,1987. It is an autonomous organization headed by Managing Director. CRIS is mainly aproject oriented organization engaged in development of major computer systems on the

Railways. CRIS has acquired special knowledge and expertise in the field of informatics.With such a rich practical experience, a dedicated team of professionals and its own R&Deffort. At present Indian Railways is one of the most advanced ministries in India, withan innovative and extensive IT environment.

RCIL

OFC

G 703 V.35 switch

Patchcard(RJ47)

LTS

SERVERSWITCH

ROUTER

G 703 V.35

PRS (LOCAL TERMINAL SERVER)

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TERMINALS

BSNL Line

J panel(Inbuilt)

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Passenger Reservation System (PRS) & UTS:

A countrywide online passenger reservation and ticketing system developed andmaintained by CRIS, is a complex online distributed client server application developedin C and Fortran programming languages on Digital OpenVMS operating system usingRTR (Reliable Transaction Router) as middleware. CONCERT (Country-wide Networkof Computerized Enhanced Reservation & Ticketing) interconnects the five regionalcomputing systems at New Delhi, Mumbai, Kolkata, Chennai and Secunderabad into aNational PRS grid. It allows a passenger from any location to book train tickets from anystation to any station. It handles reservations, modifications, and cancellations / refunds.It performs reservation for over 995,000 seats and berths (peak rush as high as 1,017,000)daily. It has complex rules, validations and fare computation techniques interwoven in the

application.

The computerization of the Unreserved Ticketing System (UTS) of Indian Railways.Unreserved ticketing constitutes a major component of the Indian Railways overallticketing volume and is an important source of revenue. UTS delivers fast and efficientunreserved ticketing from dedicated counters replacing manual Printed Card Tickets/EFTs/ BPTs with centralized online sales accounting. The solution architecture lendsitself to easy integration with handheld terminals, smart cards, automatic vendingmachines, etc.

Main server of PRS is situated in Delhi. There are two channels (lines) connecting server

and hub: RCIL & BSNL (lease line). Cable used to connect the equipment is serial cable/smart cable. We distribute the line through CAT-5 cable. There is one router, whichselects the shortest available path for data transmission. The switch is used to increase thenumber of connections and these connections are given by JET Panel.

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from the remote monitor of the test room is accepted by the DTMF decoder and the microcontroller executes the function and sends the response in the form of DTMF codes to theremote monitor. The connection to this circuit is made through the Mother Board for easywiring.

ABBREVIATIONS

ADM Add/Drop MultiplexerAUX Auxiliary AlarmCID Consecutive Identical DigitECC Embedded Communications ChannelEMC Electromagnetic CompatibilityGFP Generic Framing ProcedureID IdentificationIEC International Electro technical

Commission

I/O Input/OutputIP Internet ProtocolITU International Telecommunication UnionLAPS Link Access Procedure - SDHLED Light Emitting DiodeMAC Media Access ControlMDI Media Dependent InterfaceMDIX MDI cross-overMTBF Mean Time between FailuresMLM Multi Longitudinal Mode LaserMPLS Multi-Protocol Label Switching

NA Not ApplicablePIN P-doped, Intrinsic, N-dopedPPP Point-to-Point ProtocolPRC Primary Reference ClockRFC Request for CommentsSDH Synchronous Digital HierarchySEC Synchronous Equipment ClockSFP Small Form PluggableSIR Signal / Interference RatioSLM Single Longitudinal Mode LaserSNC/I Inherently monitored Sub-Network

Connection protectionSNMP Simple Network Management ProtocolSTM Synchronous Transport ModuleTCP Transmission Control ProtocolTDEV Time DeviationTM Time MultiplexerTRIB TributaryUDP User Datagram Protocol

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CONCLUSION

Indian Railways is the largest rail network in Asia and the worlds second largest under

one management.

This Signal and telecommunication is the most important field in Railway. It deals with

the Control, Exchange, Unreserved ticketing system and Passenger reservation system

etc.

The control of the train is controlled by the control room. They use various techniques

and softwares to deal with it. A new technology is introduced in Railway is VSAT that is

very small aperture terminal by which any person in control room can deal with the

accidental remote area. Earlier it takes hours to reach to the accidental areas.

Earlier we use Omni bus communication which was full of losses and coaxial cobles. The

overhead lines were used. Now we use quad cables, which have better efficiency and less

loss. In some parts we also use Optical fiber cable.

In exchange, railway provides its own telephone network in its offices. It has its own

broadband internet facility, which they provide in their offices.

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REFERENCES

www.en.wikipedia.org

www.en.wikipedia.org

www.indianrailways.gov.in/indianrailways/indexhome.jsp

Railway Manual for ISDN.

Indian Railway Chapter V for train traffic control.

http://www.en.wikipedia.org/http://www.indianrailways.gov.in/indianrailways/indexhome.jsphttp://www.en.wikipedia.org/http://www.indianrailways.gov.in/indianrailways/indexhome.jsp