TABLE OF CONTENTS

Acknowledgement

Preface

Introduction To Indian Railways.

Module 1: Microwave Communication.

Module 2: Railway Signalling And Signal Workshop.

Conclusion

1

Acknowledgement

Behind the completion of any successful work there lies the contribution

of not one but many individuals who may have directly or indirectly contributed

to it.

First and foremost I am grateful to the management of NORTH

EASTERN RAILWAY,GORAKHPUR for providing me the opportunity to

undertake my “Summer Industrial Training” in the organization.I specially

convey my thanks to all the staff members for their precious guidance during

our training and in completion of this project. I feel priviledged to express my

deep regards and gratitude to all the Engineers and staffs of MICROWAVE

CENTRE,N.E RLY,GORAKHPUR and SIGNAL WORKSHOP,N.E

RLY,GORAKHPUR.

I am thankful to all my teachers who have best owed upon me their

knowledge and have been guiding light through out my course. They have cast

an indelible impression on my existence.

I am much indent to my friends whose moral support always inspired me

to come out with the best.It’s great pleasure to extend my heartfelt thanks to

everybody who helped me through the successful completion of my training.

The acknowledgement would be incomplete if I fail to express deep sense

of my obligation and reverence to my parents without whom this work would

not have seen the light of the day.

Akhilesh kumar singh

2

Preface

Engineering students gain theoretical knowledge only through books. Only

theoretical knowledge is not sufficient for absolute mastery in any field.

Theoretical knowledge in our books is not of much use without knowing its

practical implementation. It has been experienced that theoretical knowledge is

volatile in nature; however practical knowledge imparts solid foundation in our

mind.

The practical industrial training is a part of four year degree

course.Practical industrial training mainly aims at making one aware of

industrial environment which means that one gets to know the

limitations,constraints and freedom under which an engineer works.

To accomplish this aspect “Gautam Buddh Technical University (GBTU), Lucknow(U.P.)” has included 4 weeks summer training for B.Tech 3rd Year students in our curriculm.

This report is infact a summary of, what I have learnt and seen during my

training in N.E Railways. It simply summarizes the Microwave communication,

signaling and signal workshop as carried out in Indian railways.The training

mainly involves industrial and complete knowledge about designing,assembling

and manufacturing of equipments.Thus it is very necessary before becoming a

professional engineer.

INDIAN RAILWAYS

3

FOUNDED - 16TH APRIL,1853

HEADQUARTER - New Delhi,India

AREA SERVED - India

INDUSTRY - Railway and Locomotives

SERVICES - Rail Transport

REVENUE - Rs. 107.66 billion

EMPLOYEES - 1,406,430

INDIAN RAILWAYS(BHARTIYA RAIL) abbreviated as IR,is a state

owned railway company of India,which owns and operate most of the

country’s rail transport.It is overseen by Ministry of Railways and

Government of India.

Indian Railways has one of the largest and busiest rail networks in the

world,transporting over 18 million passengers and more than two million tones

of freight daily.It is the world’s largest commercial or utility employer,with

more than 1.4 million employees.The railways traverse the length and breadth

of the country,covering 6,909 stations over a total route length of more than

63,327 kms (39,350 miles).As to rolling stock,IR owns over 20,000 freight

4

wagons, 50,000 coaches and 8,000 locomotives.Railways were first introduced

to India in 1853.By 1947,the year of India’s independence,there were 42 rail

systems.In 1951,the systems were nationalized as one unit,becoming one of the

largest networks in the world.IR operates both long distance and sub-urban rail

systems on a multi-gauge network of broad,meter and narrow gauges.It also

owns locomotives and coach production facilities.

As the economy of India improved,almost all railway production units

were ‘Indigenized’(produced in India).By 1985,steam locomotives were phased

out in favour of Diesel and Electric locomotive.The entire railway reservation

system was streamlined with computerization between 1987 and 1995.

In 2003,the Indian Railways celebrated 150 years of its

existence.Various zones of the railways celebrated the event by running

Heritage trains on routes similar to the ones on which the first trains on the

zones ran.The Ministry of Railway commemorated the event by launching a

special logo celebrating the completion of 150 years of service.Also launched

was a new mascot for the 150 th year celebrations,named “Bholu,the Guard

Elephant”.

Snapshots :-

It encompasses 6,909 stations over a total route length of

more than

63,028 kilometres of route length and a track length of 111,600 km .

It is one of the world's largest commercial or utility employers,

with more than 1.6 million employees.

5

It grossed a revenue of ` 88,355 cr and bagging a net income

of ` 951 cr in

the financial year 2009-10 .

It moves 2 million tons of freight & 20 million people daily

across the

county with the help of 200,000 (freight) wagons.

7,000 passenger trains across the country services 20 million

people to

their destinations .

Vivek Sahai is the current Chairman of Railway Board .

Organizational Structure-:

Indian Railways is a department owned and controlled by the Government of

India, the Ministry of Railways . IR is administered by the Railway Board,

which has a financial commissioner, five members and a chairman.

Railway zones :-

IR 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 67

divisions under 16 zones , presently operating in the country .

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Each of the 16 zones, is headed by a General Manager (GM) who reports

directly to the Railway Board. The zones are further divided into divisions

under the control of Divisional Railway Managers (DRM). The divisional

officers of engineering, mechanical, electrical, signal and telecommunication,

accounts, personnel, operating, commercial and safety branches report to

the respective Divisional Manager and are in charge of operation and

maintenance of assets.

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Further down the hierarchy tree are the Station Masters who control individual

stations and the train movement through the track territory under their stations'

administration.

Practical Training under NER :-

We've received the scheduled Summer Practical Training, as a part of our

curriculum, from June 22, 2010 – July 12, 2010 under Divisional Railway

Manager,NER,Gorakhpur.

.

We've studied about the following operational technologies in the IR -

1. Microwave Communication & Links.

2. Railway Signalling.

3. Signal Workshop(Automatic track changer,Electronic point machines and

relays)

8

MODULE I

MICROWAVE COMMUNICATION

Microwaves are electromagnetic waves whose frequencies range from 1 GHz

to 1000 GHz. Microwaves are so called since they are defined in terms of their

wave -length.There are large number of bands in microwave region.

Microwaves are used for controlling of trains.It is necessary to give correct

running and stopping of the trains and there should be a single train on a single

track.

Microwaves help the railway staff to communicate for this purpose.Stations on

average of 40km can communicate with each other by microwave.there are

large number of bands in microwave region. Before the advent of fiber optics,

these microwaves formed the heart of the long distance telephone transmission

system.

➔ In its simplest form the microwave link can be one hop, consisting

of one pair of antennas spaced as little as one or two kilometers

apart, or can be a backbone, including multiple hops, spanning

several thousand kilometers.

➔ A single hop is typically 30 to 60 km in relatively flat regions for

frequencies in the 2 to 8 GHz bands. When antennas are placed

between mountain peaks, a very long hop length can be achieved.

Hop distances in excess of 200 km are in

existence.

➔ 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.

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Microwave Transmitter and Receiver-:

Below figure shows block diagram of microwave link transmitter and receiver

section --

➔ 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.

➔ 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.

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Microwave Transmitter and Receiver.

Application Of Microwave In Indian Railways -:

Microwaves are used for controlling of trains.

It is necessary to give correct running and stopping of the trains and there

should be a single train on a single track.

Microwave communication help the railway staff to communicate for this

purpose.

Stations on average of 40 km can communicate with each other by

microwave.

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Frequency Range In Microwave Region-:

BANDS FREQUENCY(GHZ)

L 1.1-1.7

LS 1.7-2.6

S 2.6-3.9

C 3.9-8.0

X 8.0-12.5

Ku 12.5-18.0

K 18.0-26.0

Ka 26.0-40.0

How Terrestrial Microwave Transfer And Receive Data :

Terrestrial microwaves communication employs earth based transmitters

and receivers to transfer and receive data.

The frequencies used are in the low giga-hertz range,which limits all

communication to line of sight.

Examples of terrestrial microwave equipment-Telephone relay

towers,which are placed every few miles to relay telephone signals across

country.

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Antennas Are Used To Transfer Data -:

Microwave transmissions typically use a parabolic antenna that

produces a narrow,highly directional signals.

A similar antenna at the receiving site is sensitive to signals only within a

narrow focus.

Because the transmitter and receiver are highly focused,they must be

adjusted carefully so that the transmitted signal is aligned with the

receiver.

Role Of Microwaves In Passenger Reservation System -:

In PRS,the Gorakhpur Zone is connected to the main server through

communication lines and there is the need of non stop working of PRS in

Indian Railways otherwise there will be big loss to Indian

Railways.

So to increase the reliability of PRS,the main server is also connected to

the zones through microwave links.In case if there is a failure in the

physical mediathen the PRS can be operated by microwave.

Microwave Systems -:

There are two types of Microwave Systems.In first schematic processing is in

analog form and in second schematic processing is in digital form.

According to this there are two types of microwave systems as follows-:

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1. Analog system.

2. Digital system.

The analog system is old system and digital system is new one.

Analog Systems -:

The analog system is simple and this system consists of Transmitter,Receiver

and communication media which is Microwave here.

Transmitter:

The role of Transmitter is to send the signals and it consists of following parts:-

Multiplexer(MUX):-

This is used to transmit various signals simultaneously.Here there is

many Input and there is only one output.The output of the multiplexer is

given to the Radio Equipment.

Radio Equipment:-

It receives the output of the multiplexer and then processes the

signals.This is the most important part of the transmitter and the antenna

is connected to the radio equipment directly.

Transmitting Antenna:-

This is a metallic object and this is used to transmit the signals in free

space.The antenna transmit the signals at 7 GHz in the space.Here the

antenna consists of a parabolic reflector and a Horn antenna.The antenna

is directional and directive.

Tower:-

The tower is a metallic and this is used only to give height to the antenna.

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Receiver:-

The role of receiver is to receive the signals.The receiver consists of

following parts:

Receiving Antenna:

The receiving antenna receives the incoming signal and then it gives the

signals to the mixer.

Mixer:

Here in the mixer the frequency mixing takes place and now the output

frequency is different.And the output of the mixer is given to the

Discriminator.

Discriminator:

The Discriminator seperates the signals and the demodulation process is

done here.This means that the carrier signal is removed and only the

Message signals are taken.

Demultiplexer:

The demultiplexer has only one input and here the separation process is

done and the sent signals are recovered back.

Digital Systems :

This system has a large number of advantages over analog system.This

system is a new system and uses digital technology.Digital system is

more reliable and efficient.

Digital system consists of following parts:

Transmitter-:

The transmitter of digital system is different from analog system.In this

transmitter two types of multiplexers are used which are as follows:

Primary multiplexer:

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This is the first multiplexer at the transmitter side.It multiplexes 30 voice

signals and in the digital system sixteen multiplexers are used of this

type.The output of every primary multiplexer is 2.04 Mbps.

Higher order multiplexers:

This multiplexer is big and multiplexes the signal coming from the

primary multiplexers.The output of this multiplexer is 34.368 Mbps.

Radio Equipment:-

The output of the higher order multiplexer is given to the radio

equipment.Radio equipment process these signals and make them able to

be transmitted by antenna.

Antenna-:

The antenna is same as we are using in analog system.Here also we use

horn antenna and parabolc reflector.Horn antenna is at the focus and it

send the signals to the parabolic reflector surface.After striking from the

surface,the signals are parallel and it is transmitted in such form.

Tower-:

Here also the role of tower is to give height to antenna.In Microwave

station (Gorakhpur) of Indian railways,there are two towers ,one is for

analog and the other one is for digital communication.

Receiving Antenna-:

The receiving antenna is at the receiving side,receives the signals and

sends it to radio equipment.There is line of sight communication of

microwave in between transmitting and receiving antenna.

Radio Equipment-:

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The radio receiver receives the signal coming from the antenna.Here the

signals are processed and then these signals are sent to higher order

demultiplexers.

Higher Order Demultiplexers-:

In this demultiplexer the signals are separated.And the output of this

multiplexer is given to the low level multiplexer.There is sixteen outputs

and every output has a bit rate of 2.048 Mbps.

Low level multiplexer-:

This multiplexer receives the output from the higher order multiplexer.It

has one input and thirty outputs.The output frequency rate is 0-4

KHZ.This is the frequency range of human voice.Here the original voice

signals are obtained.

Power Reqirement -:

Both systems require power for their operation.A dc current is

required for both systems.This dc current is provided by a set of

batteries.An extra set of battery is also kept for emergency.

Analog System-:Analog system requires a dc voltage of -24v for its

operation.

Digital communication-:Digital system requires a voltage of 48 v for its

operation.

Essential Environment For Analog And Digital Systems-:

There are some requirements for these systems for there proper

functioning.Following are some of the requirements:-

1. Air Conditioning.

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2.Dust Free Environment.

3.Uninterrupted Power supply.

4.Proper trained staff.

Use Of Repeaters -:

After travelling some distance the microvave gets distorted.

The Repeater is a device which is used to obtain distortion free

microwave and this clean and distortion free microwave is transmitted

again in forward direction.

Repeaters are used at the average distance of 40 km.

Fault Control Procedure -:

In a typical Railway Telecom network Scenario,following types of

Telecom Network coexists:

Transmission-:

1.Microwave/UHF Network.

2.Optical Fibre Cable Network.

3.RE Telecom Cable Control Network.

4.Railway’s Overhead Wire Control Network.

5.DOT owned Overhead wire control Network.

Switching-:

1.Electronic Telephone Exchanges.

2.Electromechanical Telephone Exchanges.

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Others-:

1.Single Channel Duplex UHF/VHF Radio Systems.

2.Multiple Access Radio Relay.

3.Pair Gain System.

4.VHF/UHF Simplex Trans-receivers.

5.Talk Back systems for Major yards.

It is indeed very necessary to established well defined Fault Control

procedures for satisfactory maintenance of such diverse Railway

Telecommunication Networks so as to meet the demanding requirements of

Indian Railways in 21st century.

Typical Telecom Fault Control Setup -:

Typical telecom fault control setupon railway shall consist of

following-:

1. Zonal Telecom Fault Control Setup.

2. Divisional Telecom Fault Control Setup.

The Zonal Telecom Fault Control Setup shall be one for entire zonal railway.

The Divisional Telecom Fault control setup shall be established in each

Division of the zonal railway.

1.Zonal Telecom Fault control setup-:

It shall be manned by Section Engineer(Telecom) in a general shift.Three

section engineers(Telecom) shall be earmarked and should man the zonal fault

control setup round the clock in case of emergencies.Following Telecom

Network shall be monitored by zonal Telecom fault control Room.

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Microwave/UHF Network on the entire zonal Railway -:

The Zonal Telecom Fault Control room shall also function as an

emergency telecom control room in case of emergencies requiring

immediate telecom facilities/restoration.The emergencies may consist of

the following-:

Major rail accidents.

Cyclones.

Breaches.

When the Zonal Telecom Fault control room function as the Emergency

Telecom Control room,the divisional Telecom fault control rooms of the

affected Division(s)shall report their positions to the Zonal Telecom Fault

control room which in turn shall advice the Telecom officials at HQs of the

latest developments.

The zonal Telecom Fault Control Room shall function under the direct control

of Dy. Chief Signal & Telecom Engineer(Microwave) or any other officer

designated by communication engineer of railway.

2.Divisional Telecom Fault Control Setup-:

The Divisional Telecom Fault Control setup shall have two components:

For monitoring all telecom networks other than Microwave/UHF called

Divisional Telecom Fault Control Room.

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For monitoring Microwave/UHF networks called Divisional Microwave

Fault Control Room.

Each of these Contol rooms shall be headed by a Senior Section

Engineer(Telecom) in a general shift.Three section engineers

(Telecom)/Jr. Engineer(Telecom)shall man the fault control room round

the clock.

Following Telecom Networks shall be monitored by the Divisional

Fault control Room-:

Optical fibre Cable Network.

RE Telecom Cable Control Network.

Railway’s Overhead wire control network.

DOT owned Overhead Wire Control Network.

Electronic Telephone Exchanges.

Electro-mechanical Telephone Exchanges.

Single channel Duplex UHF/VHF

MODULE II

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Railway Signalling & Signal Workshop

Introduction-:

Signaling is one of the most important aspects of Railway

communication. In the very early days of the railways there was no fixed

signaling to inform the driver of the state of the line ahead. Trains were driven

“on sight”. But several unpleasant incidents accentuated the need for an

efficient signaling system. Earliest system involved the Time Interval

technique. Here time intervals were imposed between trains mostly around 10

mins. But due to the frequent breakdown of trains in those days this technique

resulted in rear-end collisions. This gave rise to the fixed signaling system

wherein the track was divided into fixed sections and each section was

protected by a fixed signaling. This system is still being continued although

changes have been brought about in the basic signaling methods. Earlier

mechanical signals were used but today block signaling is through electric

instruments.

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 sameposition on the track

at the same time. To make this rule work operation of trains uses signaling

to controlmovement of trains on tracks and divides tracks into several

sections which are protected by the signals.

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Fig 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.

Locking-:

There are three types of locking

a) Direct

b) Approach

c) Route

Direct locking is available as long as a signal is clear or track is occupied or a

point is set. This is the most fundamental level of locking.

23

When signal S1 is cleared the cleared condition of the signal locks other signals

which can cause trains to run on any part of the route over which S1 allows a

train to run. Thus with S1 cleared allowing trains to move to track T1 signal S4

cannot be cleared and willbe locked as the latter also allows trains to occupy

track T1. Other form of direct locking is the locking of the point in the route for

which signal S1 is cleared. If S1 is cleared to the straight route T0 – T1 – T2

then the point P1 will be set and locked to allow a train to move on the straight

route over Point P1.Attempts to move point P1 from this position will not be

allowed and hence will be locked. Conversly if the point P1 is not set for

straight the signal S1 will be locked. The occupation of a track also locks

signals if T1 is occupied then signal S1 cannot be cleared. Signal S1 is therefore

directly locked to the cleared status of the track. Points are directly locked to

track circuits over the point zones. If the track circuit over a point zone is

occupied the it is locked so that it cannot move. This is the direct locking of the

point.

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Approach Locking -:

While ensuring safety for train running it is not only necessary to ensure that

safety is ensured over all portions of track for which signals have been given

but also over portions over track which can get occupied due to trains

approaching a signal which protects these portions of track failing to stop at this

signal. Such protection is required under the condition when the signal

protecting had not been cleared.

Flank protection and isolation -:

When a train is allowed to move by a signal it is also necessary to ensure that

no part of the train will be Involved in a side collision.

Protection in the overlap -:

When a train is approaching a signal a possibility exists that the train may fail to

stop at the signal where it is intended to stop due to mechanical failure or due to

25

human failure. While there is no absolute arrangement to control against this

eventuality a partial safety is ensured by providing a small part of the track

beyond the signal at which the train is to stop free of any conflict or obstruction

to the train if it fails to stop at the foot of the signal. Typically when train TR1

is approaching S1 it will normally be ensured that the track section onto T2 is

free of any obstruction. This includes possibility of any train from the opposite

direction reaching T2. Hence if TR1 is allowed to approach S1 it will be

ensured that the train TR2 does not at the same time approach signal S2. Any

point in this portion of the track also needs to be set and locked in the position

allowing safe movement through it. If TR1 is approaching signal S1 it will

mean point P2A must be set and locked for the straight route. The point P2A

and track T2 is referred to be in the overlap for signal S1 and locks the signal

allowing approach of a train to signal S1 if not found free. Conversely if signal

S1 is cleared any condition which can lead to the overlap from failing to remain

in the condition to maintain safety for train TR1 approaching S1 will be locked.

Release of locking -:

Signals indicate when a route which it checks is safe for a train to travel. The

safety is checked from different angles as explained above. After a signal has

been cleared for a train it is required to be put back to danger as the train moves

past it. There are two reasons for doing this-:

a) To ensure the safety of the train which has moved past.

b) To allow clearance of other signals which has been locked by it.

The release of locking is done automatically as a train moves along the route a

signal had cleared for it. The locking is released in stages-:

a) As the train moves past the signal the approach locking is brought back to

normal.

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b) As the train clears the first track after the signal the direct locking gets

released.

c) As the train moves the route locking , flank or isolation protection for the

portions of the route cleared by the train is removed.

d) After the train has come to a stop at the next signal for sufficient time to

prove that it is not moving the overlap is released. This is the normal release

with the passage of train. There can however be occasions when it is required to

cancel a signal which has been cleared and yet to be passed by the train. When

this is required the signal is canceled. When the signal is canceled it is

necessary to ensure that the locking it had enabled also get canceled. Here again

the cancellation starts from release of the approach locking followed by release

of the route locking, locking of flank and isolation and finally the overlap. The

release is done only after it is established that a train which had been

approaching the train has come to a stopped at the signal before the locking to

other signals are released.

Detection of trains -:

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. Normally the detector is fed with the signal from the

source through the rails and as long the detector receives a signal it concludes

that the track section is not occupied. If a train occupies the track section being

monitored it short circuits the track cutting off the signal from the source to the

detector. When the detector fins loss of signal from the source it concludes that

27

the section is occupied by a train. Principles of fail safety is also very well

demonstrated in this arrangement. In case of a failure like a broken wire, rail

fracture, power supply failure, failure of the source the detector will lose the

signal and conclude the section is occupied by a train. This will allow the

detection to maintain safety even under failure condition and satisfy

requirments of fail safety.

Control and drive to points -:

Points are driven by electrical motors. The motors are known as point motors

and moves point using a mechanism which including the motor is referred to as

point machine. A point machine mechanism moves switches of a point through

a mechanical arrangement of rods and gears.

Signal s-:

Signals indicate to the train drivers whether the route till the next signals is

reached is safe or not. Before a signal is cleared the signal control logic verifies

that everything is safe for a train which follows it. This will mean-:

a) All track sections over which the train will be routed is unoccupied. This is

checked by checking the status of the track circuit relays. Track proving relays

of all track sections which are clear will be picked up. By checking the status of

these relays which are referred as track relays the signaling control logic can

determine

that the route is clear.

b) Routes of any signals which conflict with the signal is not cleared and that

none of the signals have been approach locked.

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c) There is not route set over a track section conflicting with the route of the

desired signal. This is proved by checking that all track circuits over which the

signal reads is clear of route locking.

Implementation of Signaling Systems –

Train running and signaling the drivers of the trains depends to a significant

extent on mechanized equipment. The technologies used for this application

ranges from very rudimentary systems to highly sophisticated equipment. The

technologies are based to a great degree on mechanical arrangement at large

number of installations. Advanced technologies are in use on sections where

train densities are high and

specially where Railway Electrification has already been done. Technologies

used for this application are for two reasons :-

1) To ensure safety of train running.

2) To improve operational efficiency.

Basic Principles :

Safety of train running in practice means ensuring that two trains do not occupy

the same location at the same time. Since trains are bound onto Railway tracks

it means ensuring two trains do not occupy same location of the track at the

same time. This is ensured in two stages-:

1) By dividing the Railway track into sections.

2) Entry into each of these sections are controlled by suitable signaling system

which ensures through various means that when a train is signaled to Basics of

Railway Signaling.

29

3) The drivers controlling the train are signaled sufficiently in advance so that

they can stop the train before signals which are not cleared. Since trains

typically move at a speed of around 100 Km./Hr. it requires a braking distance

of 1 Km before a signal at which it is required to stop. Hence signaling system

ensures that signals are conveyed to the Drivers sufficiently in advance to bring

the train to stop safely.

4)It should not be possible to move a point when a train is over the point or is

very near to the point having picked up signal allowing the train to move over

the point likely to be moved. In addition to above various other rules are applied

to

make a signaling system safe. These rules are results of experiences gained after

accidents. Thus one rule msays that if a passenger train has to run through a line

then this run through line should be isolated from other connected lines in the

station by suitable means. This rule has been introduced to ensure that if there

is a train standing on a connected line and it starts rolling it cannot result in a

devastating collision as it is kept isolated from run through line on which high

speed train has been signaled to go through.

Basic Rules -:

The basic rules of safety in connection with train running is implemented

through various methods. The Railway Engineering is very old and, therefore,

implementation methods also are old. Availability of modern electrical &

electronic technology is gradually changing the implementation of Railway

signaling systems. The technologies used in Railway signaling system depended

on human element initially. Gradually mechanical systems were introduced

followed by electrical/electromechanical and now

electronics/electrical/electromechanical systems. The human element in

30

Railway signaling is getting reduced wore & more for improving safety and

efficiency of train operations.

The Human element :

Signaling Systems exist where setting of the point and locking of the same is

entirely manual. The locking of the point is achieved through key and lock

system.

The signals are all hand Signals. A more mechanized arrangement is where

switches turning points are connected to levers and signals are given by

mechanical arms known as semaphore signals. In both the systems the human

element ensure that the routes a train will take is not obstructed. The set person

who is clearing the signals for passage of the trains achieves this entirely

visually. The oldest signaling Systems are entirely manual where even the

checking that a route has been properly is manual.

The 50 Hz & 83&113 Hz signal source is used in a manner similar to D.C.

voltage and requires no special mention as the detector is simply a relay. In case

of 83&1/3 Hz system normally 3 phase system is used and two phases are used

on any section. The feed end gives one phase and a second phase is always fed

to the detecting relay. When the track circuited section is free the two phases

create a rotary force as in a AC electric motor. Absence of one of the phase via

the rails due to presence of a train removes the rotating force dropping the relay.

The 83&1/3 Hz track circuits is a popular track circuiting arrangement.

Electronics in Railway Signaling for improved

Safety-:

The audio frequency track circuit is the latest entrant in the field. This

arrangement feeds an Audio frequency signal which causes pick up of Relay via

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the detector. A simple Audio frequency generator is used and at the detecting

end a L.C. resonant circuit is used for picking up the desired Audio frequency

signal & rejecting others. Due to the use of high frequency it is possible to use

the Railway track as a

transmission line and use of physical insulating pieces electrically isolating one

section as "R' from 'A-B" is not required. By using resonant L.C. circuits at

suitable points the AF signal can be made to stop beyond any particular point

without the need of any insulating joint. This feature is a big advantage for this

type of track circuit as there is no need to cut Rails & insert insulating pieces.

Indian Railways but considerable difficulties, faced on account of loss of track

side equipment due to theft has rendered the system ineffective. As a corollary

to this simple arrangement, systems of continuous automatic control of trains

are also available. Such systems continuously control speed of trains through

transfer of signals from the track side to the engine. The system is quite

elaborate consisting of a receiver located in the engine and suitable transmitter

coils located on the sleepers between the track. A computer computes the

required speed of trains running on the track for ensuring safety as well as for

ensuring that trains run on time speeding as necessary or slowing when needed.

Such a system is being implemented on Metro Railway Calcutta in India for the

first time. Such systems are important for Metro Railway services where time

between two successive trains is are required to be kept very small to as much

as one min or less. Even with such small interval between trains complete safety

& punctuality can be attained using the continuous automatic train control and

protection system. Use of Electrical/Electronic Gadgets for ease of operation

Over and above allowing higher levels of safety by using sophisticated controls

the use of electrical/electronic gadgets for Railway Signaling is also made for

ease of train operations and higher efficiencies. Systems known as Panel

Interlocking and its sophisticated variety known a Route Relay Interlocking are

for control of signals and points with higher efficiencies.

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Design of Signaling Circuits -:

The design of signaling circuits is based on simple principles. Railway

Signaling being one of the oldest control engineering is based on very simple

methods

and principles. One of the main reasons of its simplicity lies in the fact that

technological aids for design were not very high till late 21st century and

complicated design principles and methods could not be supported. as a result

of this the circuits are drawn using very simple symbols and names are kept

short. If looked in the context of the fact that the circuits had to be hand drawn

in times where duplicating facilities were very primitive the reason why they

are so simple

can easily be understood. Signaling circuits are based on defining relays of the

following types-:

a) Those signifying states in progress of a command

b) Those indicating steady state of the signaling functions.

c) The last operation has been completed properly .All circuits of Railway

Signaling has to ensure safety. Hence both the type of relays defined above also

always ensure safety. This fundamentally means that in absence of any voltage

to the circuit the relays shall assume safe state which is the drop state for all

neutral relays and can be dropped or one of the latched state for relays which

are latched electrically or mechanically.

Signal Workshop -:

In the signal workshop of Indian railways,following machine are

manufactured which are used as a part of signaling system-:

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1. Electric point machine.

2. Relays.

Points are provided to divert the running trains from one track to another. The

points have movable switches which can be operated electrically by a point

machine. A point can be single-ended point or double-ended point depending on

whether the movable switches are provided at one end or two ends of the point,

The two switch rails of the point are rigidly connected together by a cross bar so

that they can be moved from one position to the other position together by the

point machine. If the position of the switches is such that the train is moved on

to the main line as shown above, then the point is said to be in its normal (N)

position. If the switch rails are moved to the other position as shown below so

that the train is diverted to the loop line, then the point is said to be in its

REVERSE (R) position.

Solid State Interlocking -:

Solid State Interlocking is a data-driven signal control system designed for use

throughout the British railway system. SSI is a replacement for

electromechanical interlockings---which are based on highly reliable relay

technology---and has been designed with a view to modularity, improved

flexibility in serving the needs of a diversity of rail traffic, and greater

economy. The hugely complex relay circuitry found in many modern signalling

installations is expensive to install, difficult to modify, and requires extensive

housing---but the same functionality can be achieved with a relatively small

number of interconnected solid state elements as long as they are individually

sufficiently reliable. SSI has been designed to be compatible with current

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signalling practice and principles of interlocking design, and to maintain the

operator's perception of the behavior and appe arance of the control system.

A schematic view of SSI processor.

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Conclusion

This report takes a pedagogical stance in demonstrating how results from

theoretical electronics may be applied to yield significant insight into the

behavior of the devices .Electronics & communication engineering practice

seeks to put in place, and that this is immediately attainable with the present

state of the art. The focus for this detailed study is provided by the type of solid

state signaling and various communication systems currently being deployed

throughout mainline railways. Safety and system reliability concerns dominate

in this domain. With such motivation, two issues are tackled: the special

problem of software quality assurance in these data-driven control systems, and

the broader problem of design dependability. In the former case, the analysis is

directed towards proving safety properties of the geographic data which encode

the control logic for the railway interlocking; the latter examines the fidelity of

the communication protocols upon which the distributed control system

depends.

We have covered in this report the history ,latest developments in Railway

systems as well as related fields. We have studied the various uses of

electronics and communications in railways like microwave

communication,signaling,electronic point machines etc..

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