ABSTRACT

Practical training is necessary requirement for engineering students. According to the rules

of Rajasthan Technical University, Kota, Rajasthan, 3rd year students after their exams are

over are required to undergo the practical training of 45 days in their summer vacations. In

this respect I took my practical training at North-Western Railway, Jaipur Division.

The training at Indian Railway was very much interesting and educating. I learned

about various technologies under use and their implementation and about the various

instruments used in the industry.

We learned about Signalling to adjust traffic. Next we learned about various form of

communication such as Microwave Communication, Optical Fibre Communication.

In the next section we learned about the communication between various terminals

of indian railway system is governed by the Electornic Exchange designed and maintained

by Indian Railways. For checking the status of trains and other issues related to timing and

arrival- departure is done by another system called the Railnet which is exclusively

provided to cater to these needs.

The last section consists of the general idea of the functioning of passenger

reservation system (PRS) and detail information of the software used to establish an

interactive voice respond system (IVRS).

1

CHAPTER 1

INDIAN RAILWAYS ORGANISATIONALSTRUCTURE

1.1 Introduction:

Indian Railways (Hindi: भा�रती�य र�ल Bharatiya Rail), is a departmental undertaking of

Government of India, which owns and operates most of India's rail transport. It is overseen

by the Ministry of Railways of the Government of India.

The formal inauguration ceremony of Indian Railways was performed on 16th April

1853 with the first passenger train steamed out of Howrah station destined for Hooghly, a

distance of 36 km, on 15th August, 1854

It encompasses 7,052 stations over a total route length of more than 62,480

kilometers of route length and a track length of 1,11,600 km. It is one of the world's

largest commercial or utility employers, with more than 1.6 million employees.

It grossed revenue of 88,355 crores and bagging a net income of 951cr in the

financial year 2009-10. It moves 2 million tons of freight & 20 million people daily across

the county with the help of 2,00,000 (freight) wagons. 7,000 passenger trains across the

country services 20 million people to their destinations.

The North Western Railway is one of the sixteen railway zones in India. It is

headquartered at Jaipur. It comprises four divisions: Jodhpur and reorganized Bikaner

division of the erstwhile Northern Railway and reorganized Jaipur and Ajmer divisions of

the erstwhile Western Railway. This zone came into existence on October 1, 2002. This

railway comprises a total of 578 stations covering a total of 5449.29 route km out of which

2575.03 are broad gauge and 2874.23 are metre gauge.

2

1.2 CENTRAL RAILWAY ZONE:

Sl. No

Name Abbr. Date Established

Headquarters Division

1. Central CR 1951, November 05

Mumbai Mumbai, Bhusawal, Pune, Solapur, Nagpur

2. East Central

ECR 2002, October 01

Hajipur Danapur, Dhanbad, Mughalsarai, Samastipur, Sonpur

3. East Coast ECOR 2003, April 01 Bhubaneswar Khurda Road, Sambalpur, Visakhapatnam

4. Eastern ER 1952, April Kolkata Howrah, Sealdah, Asansol, Malda

5. North Central

NCR 2003, April 01 Allahabad Allahabad, Agra, Jhansi

6. North Eastern

NER 1952 Gorakhpur Izzatnagar, Lucknow, Varanasi

7. North Western

NWR 2002, October 1 Jaipur Jaipur, Ajmer, Bikaner, Jodhpur

8. Northeast Frontier

NFR 1958,15th Jan Guwahati Alipurduar, Katihar, Rangia, Lumding, Tinsukia

9. Northern NR 1952, April 14 Delhi Delhi, Ambala, Firozpur, Lucknow, Moradabad

10. South Central

SCR 1966, October 02

Secunderabad Secunderabad, Hyderabad, Guntakal, Guntur, Nanded, Vijayawada

11. South East Central

SECR 2003, April 01 Bilaspur Bilaspur, Raipur, Nagpur

12. South Eastern

SER 1955 Kolkata Adra, Chakradharpur, Kharagpur, Ranchi

13. South Western

SWR 2003, April 01 Hubli Hubli, Bangalore, Mysore

14. Southern SR 1951, April 14 Chennai Chennai, Tiruchirappalli, Madurai, Palakkad, Salem, Trivandrum (Thiruvananthapuram)

15. West Central

WCR 2003, April 01 Jabalpur Jabalpur, Bhopal, Kota

16. Western WR 1951, November 05

Mumbai Mumbai Central, Ratlam, Ahmedabad, Rajkot, Bhavnagar, Vadodara

Table 1.1

CENTRAL ZONE OF RAILWAY

3

1.3 INDIAN RAILWAY FACTS:

1. No. of Railway Zones 16

2. No. of Division 65

3. No. of Railway Station 7052

4. No. of passengers train 7356

5. Total Rail Route 62,480 km

6. Total Railways Employees 1.6 million

7. No. of passengers travelling per day 11 million

Table 1.2

FACTS OF INDIAN RAILWAY

Each zone also manages the workshops that are part of it. This does not include the

Production Units, which are managed by General Managers reporting directly to the

Railway Board.

CHAPTER 2

4

MICROWAVE COMMUNICATION

2.1 INTRODUCTION

Communication refers to the sending, receiving and processing of information - by

electronic means. The information signal that has to be transmitted is initially in a speech

form, for transmission this information is first converted into electrical form. Now these

signals are transmitted by any of the methods like satellite communication, microwave

communication, O.F.C., underground cable etc. The received signal at the receiver is again

in electrical form and has to be converted into usable form.

The objective of microwave communication systems is to transmit information from

one place to another without interruption, and clear reproduction at the receiver. Above 100

MHz the waves travel in straight lines and can therefore be narrowly focused. Concentrating

all the energy into a small beam using a parabolic antenna (like the satellite TV dish) gives

a much higher signal to noise ratio, but the transmitting and receiving antennas must be

accurately aligned with each other. Before the advent of fiber optics, these microwaves

formed the heart of the long distance telephone transmission system.

The "line-of-sight" nature of microwaves has some very attractive advantages over

cable systems. Line of sight is a term which is only partially correct when describing

microwave paths.

Atmospheric conditions and certain effects modify the propagation of microwaves so

that even if the designer can see from point A to point B (true line of sight), it may not be

possible to place antennas at those two points and achieve a satisfactory communication

performance.

The voice, video, or data channels are combined by a technique known as

multiplexing to produce a BB signal. This signal is frequency modulated to an IF and then

up converted (heterodyned) to the RF for transmission through the atmosphere.

The reverse process occurs at the receiver. The microwave transmission frequencies

are within the approximate range 2 to 24 GHz.

5

The frequency bands used for digital microwave radio are recommended by the

CCIR. Each recommendation clearly defines the frequency range, the number of channels

that can be used within that range, the channel spacing the bit rate and the polarization

possibilities.

2.2 What is MICROWAVE?

It is a multi-channel directional narrow band radio relay system. The Microwave frequency

spectrum is usually taken to extend from 1 GHz to 300 GHz.

It is having 100% hot standby system with space diversity provision.

The modulation is QPSK (quadrature phase shift keying).

Independent switching for Transmitter and Receiver direction.

To avoid over reach interference 4 to 6 frequency plan is used.

2.2.1 FEATURES:

1. Frequency - 7.125 - 7.425 GHz.

2. Channel capacity

Main Channel - 480 Channels

Way station Channel - 30 Channel

Digital service channel - 4 Channel

One station channel used empress order wire.

3. It employs remote supervision technique.

4. There are ASC & DSC channel are for maintains.

5. 1+1 not standby with space diversity along with automatic change over.

6. Fully solid state, MW integrated circuits, dielectric regenerator, oscillator & high-

speed digital integrated circuits is used for high efficiency.

7. QPSK modulation along with transmission.

8. It operates with -48 DC supply & positive terminal grounded.

9. In Hop due to flat fading the space diversity & bit combiner place an important part.

10. Transversal equalizer is used to prevent Band amplitude & delay Distortion due to

Frequency selective fading.

2.2.2 Advantages:

1) Circuit quality is independent from link length due to regenerative system,

6

typical regenerative spacing is close to 50km.

2) Reliability of circuit is very high i.e. efficiency is 99.999%.

3) Power consumption is less i.e. 144 watts at -48vdc and the variation of voltage

allowed is -36 to -75 volts.

4) High quality of secrecy is to be maintained.

5) Compatible for handling the data of modern electronic equipment without interface.

2.2.3 Disadvantages:

1) The propagation distortion is developed due to rain and atmospheric condition.

2) Multi-path fading occurs due to selective fading developed due to change in

atmospheric condition, and can be reduced by using diversity.

3) Interference due to radar and satellite.

2.3 FREQUENCY SPECTRUM:

Used as Frequency Band

1. Voice frequency range 300 Hz to 3400 Hz

2. Audible Frequency Range 20 Hz to 20 KHz

3. Very Low Frequency (VLF) 3 KHz to 30 KHz

4. Low Frequency (LF) 30 KHz to 300 KHz

5. Medium Frequency (MF) 300 KHz to 3MHz

6. High Frequency (HF) 3MHz to 30 MHz

7. Very High Frequency (VHF) 30MHz to 300 MHz

8. Ultra High Frequency (UHF) 300 MHz to 3 GHz

9. Super High Frequency (SHF) 3 GHz to 30 GHz

10. External High Frequency (HF) 30 GHz to 300 GHz

Table 2.1FREQUENCY SPECTRUM

2.4 MICROWAVE PROPAGATION:

1. The microwave propagation takes place through space waves in troposphere, which

7

is within 10km on earth level, so attenuation is very large but due to directivity of

antenna and high receiver sensitivity the system is very satisfactory.

2. MW antenna is directive due to parabolic reflector so maximum radio power is

concentrated in one direction it is a line of sight communication. Thus low power

MW signal can also travel a long distance path.

3. Due to directive antenna the signal is not spread, so interference of other

communication system is very negligible.

4. At MW frequency there is no atmospheric or manmade noise. The only noise is

thermal noise.

5. It also follows the properties of light as absorption, reflection, refraction, diffraction

and scattering.

2.5 DATA PROCESSING:

2.5.1 Principle:

Information signals to be transmitted are first pulse code modulated, multiplexed, then

undergone through QPSK modulation.

2.5.2 Pulse code Modulation (PCM):

In PCM system since speech signal is band limited to 300-400Hz, a sampling rate of 8000

samples per second and a bit rate of 8 bits per sample are almost a worldwide standard.

A practical PCM system used in INDIAN RAILWAYS has 30 channels for speech

or data and 2 channels for signaling and synchronization. This system thus results in a data

stream of 2.048 Mbps. Higher order multiplexing of 16 such data streams results in a

34Mbps data stream. This is then converted into an IF signal with freq. 70MHz and then

QPSK modulated with carrier at freq 7181.696MHz. This signal is finally transmitted by

means of antenna having parabolic reflector.

2.5.3 Practical Implication:

Information signals to be transmitted into the space by antenna are first passed through

following stages:

A) Primary digital MUX:

In this stage 30 channels are undergone through PCM-DM process to obtain a 2.048 Mbps

8

data stream. Information coming from exchange is fed to the PDMX through Kron tag

block and data related to Rail Net, FOIS, PRS are fed through modem.

Ajmer station has in bridge 3630 multiplexers from inducer communication Ltd. as

PDMX.

System configuration:

It consists of following units:-

Power Supply Unit:

Input to power supply unit is -48 V while the outputs are

a) +5V

b) -5v

c) +15V

d) -15V

Universal Card:

It is the motherboard that consists of 16 slots of champ connector for Mounting

the Interface cards. In addition to housing the interface modules it handles the

various controls, timing and data signals.

Control Card:

It is a Motorola 68008 processor controlled card. It is an 8-bit processor and an

8MHz clock is used. It has a 640 K EPROM, 256 K DROM, 32 K non-volatile

RAM, 2 line interface modules. It provides,

a) Switching operation

b) Synchronization and clock recovery

c) Diagnostics

d) State monitoring

Interface Card:

These cards accept or give analog or digital input/output from/to the outside

world and give the process of PCM completed in this card. Each 3 d caters for

two terminations.

In this PCM system, the encoder output is converted into a suitable code to etch the

characteristics of the transmission media. The code is HDB-3 Code: High Density Bipolar

9

Code of order 3.

B) Higher order MUX:

The 2.048Mbps streams obtained from various PDMUX'S are fed to the higher order

MUX, which gives a 34 Mbps data stream at its output. System configuration and principle

of working of this MUX is same as that PDMX

C) Radio equipment:

It is fully solid-state microwaves PCM transmitter-receiver employing x microwave

integrated circuits (MIC) for the RF circuit and field effect transistors (FET) for the low

noise microwave amplifier.

The TRP-7G34MB-770 Digital Transmitter-Receiver, With switch over units

provides highly efficient transmission services in the 7GHz radio frequency band (7125 to

7725 MHz) which have a transmission capacity of 34 Mbps digital signal.

2.6 OPERATION:

The data signals are received, amplified, and re-transmitted by each of these stations.

Microwave Transmitter and Receiver Below figure shows block diagram of microwave link

transmitter and receiver section –

Fig 2.1DIGITAL REPEATER AND MICROWAVE LINK

10

In order to overcome the problems of line-of-sight and power amplification of weak

signals, microwave systems use repeaters at intervals of about 25 to 30 km in between the

transmitting receiving stations.

The first repeater is placed in line-of-sight of the transmitting station and the last

repeater is placed in line-of-sight of the receiving station. Two consecutive repeaters are

also placed in line-of-sight of each other.

A. TRANSMITTER SIDE:-

TX DPU: TX DPU consists of:

Line Equalizer Circuit: The HDB3-coded signal is distorted by inter- connecting

cable; so an equalizing circuit is given to compensate that distortion and to keep

the output amplitude constant. This circuit caters for 20 db loss.

HDB-3to unipolar converter: In this stage, the incoming 34 Mbps signal with

HDB-3 code format is converted to a unipolar signal and clock is extracted.

Serial-parallel converter: The 34.368Mbps signal is applied to two memories and

readout using 1/2 divided clock. The two streams will be at the rate of 17.184

Mbps.

Rate converter: Rate conversion of data from 17.184 to 19.332 Mbps enables

stuffing of parity, framing, DSC, and wayside signals.

Multiplexers: The function of mux is to combine digital service channel along

with Dl, D2.

TRANSMITTER: - It comprises following modules:

Phase modulator (PH MOD): The two streams of 19.332 MBPS from Tx DPU

is applied to the PH- MOD where it is converted into a 70Mhz IF signal.

Transmitter radio freq. Circuit (Tx RF): The IF signal is applied to TX RF

circuit where it is mixed with an RF local signal from VCO at 7GHz to produce

the transmitting frequency and then is applied to FET amplifier circuit for

amplification up to specified level.

11

B. RECEIVER SIDE:

Receiver RF circuit: It consists of

1) Pre RF amplifier: After passing through microwave branching filter where

the undesired signal is eliminated, the received microwave signal is

amplified by low noise RF pre amplifier.

2) Receiver frequency converter: Here the amplified signal is converted to

70MHz IF signal by mixing with a receiver local signal supplied from the

receiver local oscillator.

Receiver IF circuit: The converted 70MHz IF signal is fed to the Rx IF circuit

through a delay equalizer which equalizes on a hop basis, the system delay

caused by filtering in the Tx-Rx and the RF branching circuit. Receiver IF circuit

consists of receiver IF amplifier. It adopts AGC circuitry PIN diodes with the

dynamic range of more than 50Db. This keeps the IF output constant.

Demodulator: The DEM comprises the phase modulator and bit compiler. The

received IF signal is applied to the PII-DEM and converted to two binary coded

pulse streams and the converted pulse streams from the PH-DFM are send to the

Rx DPIJ through bit combiner which accomplishes a hitless switching action so

as to select one of the two data signals.

Rx DPU: It consists of demultiplexer, parallel to serial converter, unipolar to

HDB-3 converter. It functions reversely to the Tx DPU.

Tx and Rx switch over: At the transmitter side one PCM signal led from the

transmitters. At the receiving side the higher quality route is automatically

selected using an alarm signal from the DPU. The alarm signal is issued when

the bit error rate degrades to the pre selected value.

2.6.1 PATH LOSS:

The information signal radiated in the space by antenna, undergoes through free space loss

which depends upon the frequency of transmission and distance traveled in following

manner,

Thus in order to maintain the signal quality despite of such losses max distances

between two mw stations is kept 50Km. This distance is called Hop distance.

12

Free Space Loss = 32.5 + 20 log f (MHz) + 20 log D(Km)

2.6.2 GENERATOR AND BATTERY ROOM:

In absence of electric supply from JAIPUR VIDHYUT VITRAN NIGAM, a 10 KVA

generator is used. This generator possesses an alternator, 4 stroke compressor, diesel tank

and fuel pump.

In battery room 24 batteries, each of 2.2V, are connected in series. Thus we get a DC

supply of 48V with capacity of 525 AH.

There are two sets of such batteries to provide uninterrupted constant DC supply. At a

time one set is on load and other is on charging.

The extent, to which batteries are charged, is estimated by measuring the specific

gravity of the sulphuric acid solution using Hydrometer. Specific gravity of 1200 is

considered as standard for charged battery.

2.6.3 DEHYDRATOR:

There at microwave station we use a dehydrator plant, which absorbs the moisture inside

the waveguides. Waveguides are elliptical in shape. The dehydrator bulb possesses silica

gel. In fresh condition silica gel is blue colored but after absorbing moisture it becomes pink

in colour.

2.6.4 NETWORK MANAGEMENT SYSTEM:

NMS software has 8 main external and 8 internal commands. There are master stations and

sub master station. Jaipur and Ajmer are sub master stations while Ahemdabad is a master

station. There are 19 stations between ADI arid JP. From master station we can check

transmission and receiving status. These external and internal commands can be used to

change the critical values/level of any station. We have facility of battery change over

charger ON-OFF, generator ON-OFF right from master station using these commands.

2.6.5 REPEATER STATIONS:

They are of two types:

A. Regenerative Repeater:

A repeater is considered to be regenerative if the received signal from one side goes

through the complete process of modulation-demodulation, regeneration process.

Since signal is demodulated and regenerated it can be fed to the MUX equipment.

Hence regenerative repeaters are used at dropping-inserting stations.

13

B. Non-Regenerative Repeater:

A heterodyne receiver can be used as a non-regenerative repeater. A disadvantage is

that noise and signal distortion accumulate from repeater to repeater.

2.7 MICROWAVE STATION:

Fig 2.2MICROWAVE STATION

14

2.8 MAINTENANCE OF MICROWAVE:The maintenance schedule prescribed as below

A) Daily:-

1) Specific grays and voltage of battery.

2) Monitoring panel level.

3) Change over battery if charge-discharge cycle is employed.

B) Weekly: -

1) Check the supervisory display panel reading.

2) Delete the Alarm on On-line computer.

C) Monthly: -

1) Antenna and aviation light.

2) Change over the transmitter and receiver.

3) Diesel generator maintenance.

4) Measurement by supply voltage, and voltage of DC-DC.

15

CHAPTER 3

AUTOMATIC ELECTRONIC EXCHANGE

3.1 ELECTRONIC EXCHANGE:

Telecom exchanges are the vital assets of the local communication networking, during the

age of information if technology telephone exchanges have a vital role for connecting

subscriber to different types of server as well as for connecting long hold subscribers

through STD network for the different type of users like FAX, video conferencing etc.

Fig. 3.1Development of Exchanges

Initially the subscribers connected through magneto telephone exchanges latter on

connected via CB exchanges its required manpower for the operation and even though

secrecy was not there.

Electromechanical exchanges are provided to over-come the above cited problems,

but due to its dear and tear, electromechanical exchanges were out dated in the same

16

sequence crossbar exchanges came and replaced due to its same reason.

Digital cross-matrix exchanges are the best replacement during the age of

information technology.

In the same sequence Digital Exchanges (OKI) is installed at divisional headquarter

as well as in Public Reservation System at northwestern division of Railway Jaipur

Electromechanical exchanges previously provided for communications at Ajmer, with

increase of communication assets like Rail net, FAX, IVRS and video conferencing these

exchanges are replaced by digital electronics exchanges.

Railway has its own communication system including microwave stations and

automatic electronic exchanges.

Jaipur Division exchange consists of three main exchanges:

First is having a capacity of 128 lines. It is based on C-DOT technology that is an

Indian technology and it is a product of RTPL (Rajasthan Telematic Pvt. Ltd.).

Second one has the capacity of 1200 lines and is based on OKI technology. It is a

collaboration product of TATA Telecom and Compton Greaves.

Third one has a capacity of 60 lines. It is a MKT (Multi Key Telephone)

exchange. It is a product from Nitsuhu-Enkay. It provides ISDN (Integrated

Switching Digital Network) facility to RLY.

3.2 C-DOT ELECTRONIC EXCHANGE:

It is an Indigenous SPC exchange developed by “Center for development of telematic, C-

DOT''. C-Dot is developed only on one microprocessor IC ice. 65C02.

128 ports C-Dot exchanges are commonly used in railways. The 128 ports exchange

has a limitation i.e. the maximum subscribers accommodations are 96 with 8 Junction lines

and can be extended up-to 24 with reduction of subscriber lines. They are: -

1. 96 subscriber lines + 8 trunk (junction) line.

2. 88 subscriber lines + 16 trunk (junction) line

3. 80 subscriber lines + 24 trunk (junction) line

17

3.3 FEATURE OF RAX 128 PORT EXCHANGE:

1) 128 terminations can be accommodated in single frame.

2) Fully digital exchange.

3) Stored program controlled.

4) Non blocking exchange.

5) Modular expansion.

6) Less installation time.

7) Flexible system dimensioning.

8) Single fault can effect not more than 8 terminations except processor portion.

9) Low power consumption.

10) Can work up to 45c, so no air-condition is required.

11) Man-machine communication by maintenance console.

12) Subscriber loop resistance is 1900 far for normal subscriber.

13) Impulse make break ratio can be accepted up to 50-80%.

14) It is design for wide range of temp., humidity, and other environmental conditions.

15) Provision of air filter to prevent the exchange from dust.

16) It is rigid so rough transport can be with stand.

17) It requires very little maintenance and has facility for central monitoring and

testing.

18) The technology is based on indigenous hardware and software, assuring full local

support for future updating.

19) Cost of the equipment is very low.

20) Technology is quit latest and compatible with other international product.

3.4 FUNCTIONS OF IMPORTANT CARDS:

3.4.1 PSU CARD:

It is switch mode power supply card worked on –48±4volts DC.

FEATURES:

1. It feeds - 48ev dc to subscriber line card and senses the flow of current in line.

lf current is more than 10mA and up to 35mA max, it is treated that subscriber

18

has lifted the handset,

lf less than 10mA the card treats as on the hook condition.

2. PSU generates other supplies for various cards through dc to dc converter.

+5V regulated (8Amp)

12V regulated (1Amp)

-5Vdc (0.1 amp) regulated

-9V (0.3Amp) unregulated

3. It also generates 75 Volt AC for ring current purpose. 12volts regulated is used

for SLC card relay operation i.e. for test relay and ring relay.

Two PSU cards share the exchange load equally, but in case of fault, the other PSU

cater the full load.

3.4.2 SUBSCRIBER LINE CARD (SLC Card): -

There are 10 SLC card. Each card contains 8 lines. They are not duplicated. In addition of

these 10 cards, there are 3 trunk cards, out of which 2-trunk cards can be replaced to 2 SLC

cards. One trunk card cannot be replaced because it is an E&M card of 4wire system. So

that maximum possible subscriber with trunk is 96+8.

FEATURES:

1. It performs the functions collectively termed as BORSCHT means:

B- Battery feed

O- Over voltage protection

R- Ringing

S- Supervision

C- Coding

H- Hybrid conversion

T- Testing

It acts as a terminal card for interfacing subscriber and exchange.

2. Each card has 8 identical circuits catering 8 subscribers.

3. Enable the voice of the subscriber to reach a port with in exchange for onward

transmission to calling and called party.

4. It has provision to operate for any of the 2 Input signals from copy '0' and copy

‘1’.

19

5. It communicates with TIC/SN card for voice data.

6. SLC communicates with SP for signaling data.

Each subscriber circuit has 2 relays. One is testing relay, which isolates subscriber

line from exchange, and now line can be checked. The other relay is ring feed relay; it feeds

the ringing current to the called party.

3.4.3 Tone generator and Diagnostic cards(TGD Card):-

The TGD generates 8 different tones to' indicate different status of the subscriber line. It

also has diagnostic circuit. TGD can diagnose the functions of the card (self-diagnoses) and

give an error-reporting signal to TIC card. When it is required to feed a tone to subscriber,

the time slot of particular tone is switched to time slot of the subscriber. Hence subscriber

hears the tone. The Tones Are:

Tone Frequency On-Off period Time out

Dial tone 400Hz +25Hz modulator Continuous 10 sec

Busy Tone 400Hz 0.75sec On;0.75sec Off 10sec

Ring back Tone 400Hz +25Hz modulator 0.4sec On;0.2sec Off 60 sec

NU Tone 400Hz 2.8sec On;0.2sec Off 60sec

Table 3.1Types of Tones

3.4.4 CONTROL CARDS: -

There are ‘3' cards, which form a control network: -

1. RCP-RAX Control Processor

2. TIC - Terminal Interface Controller

3. SP - Signal Processor

A11 the control cards are duplicated. One copy is active and other is passive. In case of

fault, the system switches over to passive copy automatically making passive copy active.

RCP, TIC, and SP form a group and at a time one group is active and other is passive. Any

20

single change over is registered on the maintenance panel.

A. RAX Control Card: -

FEATURES:

1. Main controller (master)

2. Microprocessor 65C02(C-MOS µp).

3. Performs call processing, administrative, and maintenance functions.

4. Exchange database.

5. Man-machine interaction through the maintenance panel (MP).

6. Communication links with the TIC. MP and duplicate RCP.

7. Extensive system diagnostic.

B. TIC Card/ SN (Switching Network): -

Terminal interface card and switching network is a completely non-blocking network and

allows for higher traffic handling capacity. Four PCM-32 links form the terminal group

and undergo to ‘TDM’ to generate PCM 128 channel link.

Then it is demultiplexed to regenerate the four PCM-32 links at 2MB which carry

the switched information back to terminal interface.

FEATURES: -

1. TIC/SN Card is a 128 time Slot switch, switching (PCM) digital voice

information between 128 ports to enable the subscriber to converse with each

other and feed different tones at different stage of call.

2. The microprocessor is of 8 bit i.e. 65C02 type.

3. TIC work under the instruction of RCP.

4. TIC controls SP (signal processor) and SN (switch network).

5. TIC also gathers information from SP and sends to RCP for processing.

6. Receives the processed signal from RCP for processing.

7. The card has 32kB EPROM and 16kB RAM for stretch pad.

CONNECTION:

1. SP again validates OFF-HOOK condition, if valid it is reported to TIC.

2. TIC sends a message to RCP through TP(SP)

21

3. RCP informs TIC through TP (SP) to connect ’A’ and ‘B’ (time switching) and

state of subscriber is changed to conversation.

4. RCP increments the meter of the subscriber A and one call is registered.

DISCONNECTION:

1. Subscriber ‘A’ goes “on hook''

2. Line card detects the disconnection of loop by sending “Non flow'' of current as

in the limbs.

3. This condition reported to SP.

4. SP reports the “on hook'' condition of Sub. ‘A' to TIC

5. TIC records the “on hook'' state and prepares message of disconnection and

sends it to RCP through TP reporting this message that Sub. ‘A’ has cradled on

HMT.

6. RCP sends a message to TIC through TP to disconnect subscriber A &B.

22

CHAPTER 4

SIGNALLING

4.1 INTRODUCTION:

When trains run on railway tracks they follow rules of operations in which safety plays a

very important role. The most important rule in respect of safety is to ensure that two trains

do not occupy the same position on the track at the same time. To make this rule work

operation of trains uses signaling to control movement of trains on tracks and divides tracks

into several sections which are protected by the signals.

Fig.4.1Railway Signalling Arrangement

Fig 4.1 shows a representation of a railway signaling arrangement. The horizontal

liner represents the railway track, the signals are depicted by the symbol of the circle with a

horizontal and vertical line to this circle and the red rectangles are the trains. This

representation is however to explain how trains are run safely and the actual representation

of various locking.

4.2 INTERLOCKING:

When trains are to be crossed or overtaken at stations, points and signals are to be worked in

proper sequence to make passage of trains safe and interlocking between points and signals

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TR s TR s TR s

T0 T1 T2 T3

takes care of this. Simultaneous movements in stations are also safe guarded by

interlocking.

There are three types of locking:

a) Direct

b) Approach

c) Route

At present time Route Relay Interlocking Is used because with Route Relay

Interlocking, a complete route can be set by one operation and suitably safeguarded against

conflicting moves.

4.3 TRAIN DETECTION:

Signals control movement of trains. For it to effectively control movement of signals there

is a need to know the location of trains on the track. The railway tracks are divided into

short sections normally referred to as track sections. At any time only one train can occupy

one such a section. Track circuits or axle counters are used for the detection of trains in

these sections. Only one train can occupy a track section at any time.

4.4 IPS (Integrated Power Supply):

Power supply system is the heart of signalling system. For a reliable signalling system

installation, reliable power supply system is most important.

The source of power supply is through a rural feeder, which is quite unreliable in

respect of its availability and voltage. The battery backup is provided in all the DC circuit,

which requires more maintenance. Due to frequent interruptions of supply, the signals are

becoming blank till the starting of Diesel Generators.

To overcome these problems a comprehensive power supply scheme known as

Integrated Power Supply system has been use in Indian Railway.

The function of Integrated Power Supply system is to provide a stable and reliable

AC and DC power supply to the Railway signalling installations against all AC mains

variations or even interruptions. This is very essential for proper movement of trains. As the

name indicates, it is designed and developed with a view to provide complete power

solutions from single system to all signalling circuits.

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Integrated Power Supply consists of the following:

AC-DP Panel-Alternative Current Distribution Panel

Inverters

Ferro resonant based Automatic Voltage Regulator (AVR) or Bypass CVT

Transformers

Float Cum Boost Charger Panel

FRBC (Float Rectifier cum Boost Charger) module

Distribution/Supervisory control/Alarm (DSA) unit

DC-DP Panel- Discrete Current Distribution Panel

DC-DC converters

Common Digital Voltmeter for measurement

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CHAPTER 5

RAILNET

5.1 INTRODUCTION

Indian Railways have decided to set up their own Corporate Wide Information System

(CWIS) called RAILNET to provide computer connectivity between Railway board with

Zonal Railways, Production Units, Centralized Training Institutes and Major Training

Institutes. For improvement in this network in terms of bandwidth, quality of channel,

Indian Railways setup a separate organization i.e. Indian Railways central organization for

telecommunication.

5.2 ORGANIZATION:

First RAILNET was established between RAILWAY BOARD, Zones and 6

production units in phase-1.

Then extended to 6 new zones, 5 centralized training and standard organizations,

Metropolitan transport project in phase-2.

The divisional offices, Zonal training institutes will be connected to rail net in

phase-3 and finally to station, yards, shads etc.

5.3RAILNET COMPRISES:

5.3.1 INTRA-NET:

Intra net is an internal network of Indian railway allowing the railway officers and staff to

communicate on this digitized network.

5.3.2 INTER-NET:

Internet allows user to get into a global communication method and global pool of

knowledge, advertisement and entertainment through WWW (World Wide Web) in a

secured manner.

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5.4 ADVANTAGES:

Paperless working.

Display of information and official orders.

Reliable facilities for passengers about reservation, timing & other.

5.5 NETWORK COMPONENTS:

Fig. 5.1RAILNET GENERAL ARRANGEMENT

5.5.1 SERVER:

A network is a multi-user system, because more than one person at a time can send request

to a machine. A shared machine together with the software programs which handles request

and distributes the network resources such as data files, and printer time both the machines

and its software are jointly referred as server. The characteristics of a server are:

Hardware including motherboard of the server is entirely different from a normal.

It can be used with two processor of 500MHz.

A server should be able to provide security for its data.

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5.5.2 ROUTER:

Computer translates information from one network to another. Router selects the best part to

route a message, based on the destination address and origin. The router can direct traffic to

prevent head-on collisions, and smart enough to know when to direct traffic along back

roads and short-cuts. Routers can:

Direct signal traffic efficiently.

Route messages between two any protocols.

Route messages between linear bus, star and star wired ring topologies.

Route messages across fiber optics, co-axial and twisted pair cables.

5.5.3 SWITCH:

A switch is used to interconnect the nodes, but it is more complex and versatile, and there is

no division of bandwidth among the nodes. They are active device with following points.

10 Mbps, 100 Mbps, single speed, or dual speed operation.

Switch should have enough buffers to take care of the traffic peaks.

Segmentation of local networks

5.5.4 FIREWALL:

It is security purpose software, which is used to secure the server contains, so the outside

user cannot tamper with the important data. The user can read the information, but cannot

add or remove anything from the data.

5.5.5 HUB:

It is an active junction box, which is used to connect the nodes and all the servers using any

type of cable. It contains a division of network bandwidth. The main parameters to be

considered for selecting a hub:

Supports for dual speed operation.

Number and types of ports, UTP and BNC

Auto switching

Support a built-in segment switch.

Ease of configuration.

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5.5.6 NODES:

The terminals of computers which are interconnected through switch or hubs are called

nodes.

5.6 WORKING OF RAILNET:

Rail net is similar to internet. All the computers and communication cables that make up the

thousands of smaller networks at various railway offices are connected together to form the

Rail net. It follows a simple rule, TCP/IP. Here packet switching, where a computer a

message is broken into small packets, is used. Each packet consists of a destination address,

a source address and packet identity and user data. A packet can travel through any path on

the network. Different servers of railways are connected to each other via its own

Microwave Stations to form a nationwide network of Indian Railways.

Four wires are coming from Microwave Station and they are terminated on the lease

line modem. This modem is connected to router through a cable. Router is connected to the

switch. Switch is an interface between server and router.

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CHAPTER 6

PASSENGER RESERVATION SYSTEM

6.1 INTRODUCTION:

The IR carries about 5.5lakh passengers in Reservation reserved accommodation

every day.

The computerized Passenger Reservation System (PRS) facilities booking and

cancelling of tickets from any of the 4000 terminals.

These tickets can be booked or cancelled for journeys commencing in any part of

India and ending in any other part, with travelling times as long as 72 hours and

distances up to several thousand kilometers.

There are mainly 5 servers in India. These are New Delhi, Kolkata, Chennai,

Mumbai and Secunderabad.

6.2 EQUIPMENTS:

6.2.1 Modem:

Modem is used for communication of various computers or communication between

computers and terminals over ordinary or leased (dedicated) telephone lines. We can use

modems to log on to micro, mini, main frame computer for line processing. They can also

be used to connect two remote computers for data.

How does modem work?

The modem word is derived from the words modulator and demodulator

Computers communicate in digital language while telephone lines communicate in

analog language. So an inter mediator is required which can communicate in both

languages.

Modem transmits information between computers in bit by bit stream. To represent

a bit or group of bits, modem modulates the characteristics of the wave that are

carried by telephone lines.

The rate at which modem changes these characteristics determines the transmission

speed of data transmission. The rate of modem is called bound rate.

The modem can transmit data in two forms: Asynchronous and Synchronous.

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The analog modem switch at each location is connected to analog modems of the

main as well as the stand by links.

6.2.2 Multiplexing equipment:

There are two types of multiplexing equipment for each channel. The multiplexer used may

be of 18 ports or 16 ports. The data is get multiplexed at the rate of the 96kBps. The

multiplexing is generally of analog type.

6.2.3 End Terminal:

The end terminal of the system is the station where the tickets are to be printed out. The

terminal consists of a computer system with a dot matrix printer. The number of total end

terminals at the station can be increased or decreased according to the multiplexing used.

6.3 IVRS (Interactive Voice Response System:

6.3.1 Introduction:

The system in which, the information available in the computer is retrieved by the user in

the form of voice with the help of the interaction between telephone and computer is known

as Interactive Voice Respond System (IVRS).

With the help of this system information regarding public reservation; arrival/

departure of train; fare can be delivered to user when and where it is asked through

telephone.

Each section control office is having a computer called DATA ENTRY COMPUTER

along with dial up / lease line modem which is used for linking the computer of other

control offices either directly or through server available at Church gate . Each control

office computer is identified as check / data entry point.

Information regarding the running of the train can be registered or checked at

every15minute duration.

At place where the information is to be retrieve through Telephone, another

computer is linked with data entry computer called IVRS computers which are connected to

data entry computer by ETHERNET CARD. These computers read the information from

data entry computer and then convert it to voice for user purpose.

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6.3.2 HARDWARE:

1. DATA ENTRY TERMINAL:

It is a personal computer of more than 166MHz with 16 MB RAM; 2.1 Hard disk;

101 key keyboards; a mouse & a color monitor.

2. MODEM:

The data entry terminals are linked with lease line/ dialup modem of speed better

than 33.6 KBPS.

3. IVRS TERMINAL:

It is Pentium 133 MHz P.C. with 24 port dialogic cards called IVRS card capable to

respond on both pulse and tone. Out of 24 ports, 4 ports are used for voice and FAX

on demand; 2 ports are used for railway PSTN lines; 2 ports are used for fare inquiry

and rest 16 ports are used for train inquiry.

6.3.3 SOFTWARE:

There are three types of software’s:

Copets :

It is friendly user software, which is used to record the train schedule timing in

information data files. This software is having following facilities:

1) The system is secured by 3 stages for password facility.

2) It is having the facility for data entry of running/schedule time.

3) Entry for expected arrival/departure.

4) Addition and removal of data entry points.

5) Addition and removal of train in the system.

6) Changes in the database for timetable; fare table etc.

7) This software is having a facility to generate the report of

a) Status of running train as per-

According to train

According to control office

As per a specific interval

b) Information of train, when the train is late more than specific hours.

c) Summary of any train running over the month.

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d) It also shows the train graph.

8) It restricts the entry of train after a specific period i.e. the file is deleted for a

train after 2 hours of its arrival; and deletes the files which are 48 hours old and

restructure/reorganize the files.

Communication Software:

This software works on the principle of packet switching in which each train file is

developed in the form of packet along with destination address. The important facilities

of this are:

1) Auto dialing facility for transmission of information or data.

2) Having facility of auto pickup of file from remote queue directory.

3) Facility of auto transfer of own file to remote/required place.

4) Facility to support WAN and is capable of interfacing with any type of

communication system like Internet, VHF, UHF, leased line.

5) Facility of transfer of file as per priority decided by HUB.

6) Facility of monitoring of transferred and received files.

Oltris software:

The main aim of the system is to provide “ON LINE TRAIN RUNNING

INFORMATION” like termination of the train before schedule; change the route of the

train; accident of train; abnormal delay of the train and so on. So the software is

developed to inform about all the abnormal activities.

6.3.4 ADVANTAGE OF IVRS:

1) This system is distributed architecture system, which should made available the last

data for transfer from remote to main computer and vice versa, and

2) In case of communication breakdown the local control office can be update by

support lease line / dialup modem connectivity.

3) This system includes all type of train as - Mail, Express, passenger, MEMU, DMU.

4) The system will support and report the following as missed entry, late entry status of

train and can be entry screen according to time table at a 15 minutes interval through

pop-up so that minimum entry is to be done by operator and the system is ready for

next train.

5) The IVRS software is worked on ring modules in which the translation of script is

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very easy.

CHAPTER 7

OPTICAL FIBER COMMUNICATION

Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a

human hair. They are arranged in bundles called optical cables and used to transmit light

signals over long distances.

Today's general demands to railway administrations all over the world are improved

traffic regularity, more frequent departures and, shorter travelling times

The telecommunication network has to operate with more subscribers as well as to

carry a number of new services, such as automatic train numbering, electronic

reporting and passenger information, freight control and voice channels to

radio base stations for mobile radio communication.

7.1 Internal Structure of Optical Fiber

Core – thin glass centre of the fiber where light travels.

Cladding – outer optical material surrounding the core

Buffer Coating – plastic coating that protects the fiber.

Fig. 7.1

Internal Structure of OFCs

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Fig. 7.2Constructional Structure of OFCs

7.2 Types of Optical Fiber

Optical fibers can be broadly classified in two types:

1. Single-mode fibers – used to transmit one signal per fiber (used in telephone and

cable TV). They have a small core (9 microns in diameter) and transmit infra-red

light from laser.

2. Multi-mode fibers – used to transmit many signals per fiber (used in computer

networks). They have larger core (62.5 microns in diameter) and transmit infra-red

light from LED.

7.3 Working of Optical Fiber

Optical Fibers work on the principle of total internal reflection, and hence it

doesn’t allow the signal travelling in the form of light to escape the guiding

medium. Total internal reflection tells that light travelling in a dense medium hits a

boundary at a steep angle (larger than the "critical angle" for the boundary), the light will be

completely reflected.

Fig. 7.3

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TIR in OFC

Fig 7.4Angle Reflection in OFCs

7.4 Advantages of OFCs:

Supports low bit-error rate digital communication

Very high traffic carrying capacity and hence potential for leasing excess capacity to

other users and providing other services.

Negligible cross-talk between channels.

Free from EMI and RFI making it especially useful in electrified areas.

High electrical resistance, so safe to use near high-voltage equipment or between

areas with different earth potentials.

Low loss, so repeater-less transmission over long distance is possible.

The weight of the optical fiber cable is very low, hence it is easier to transport.

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7.5

37

38

39

40

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Disadvantages of Optical Fiber

High cost.

Need of more expensive optical transmitters and receiver

7.6 Use of Optical Fibers in Indian Railways:

Telecommunication:

Local Area Network

Telecommunications

CONCLUSION

It was a great experience to be there in NORTH WESTERN RAILWAYS, JAIPUR

for my practical training and like every good thing it had to come to an end and so it did.

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During the 30 days I certainly learnt a lot about every aspect of this field right from the

working environment to the technical details of various equipment and process relating to

my branch.

Training at the Indian Railways helped us to understand the application of the

governing theory and principles in the real practical world that we have only studied in our

curriculum and how it is achieved and how to troubleshoot and debug the real life problems

faced in the industry.

The things are numerous while words are only few. To conclude I would rather say

that even after my full try I could pick up only a mouthful of knowledge out of sea. The

time was really less while there was lot to learn.

Well that’s how the life goes on. I hope I would have another chance to visit and learn

more if it.

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REFERENCES

1.) www.yahoo.com/images.

2.) Microwave Communication – Liao

3.) Wikipedia

4.) www.indianrail.gov.in

5.) www.google.com

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