A PRACTICAL TRAINING REPORT

ON

COMMUNICATION AND SIGNALLING

Taken at

WEST CENTRAL RAILWAYS, KOTA

Submitted in partial fulfillment

for the award of the degree of

BACHELOR OF TECHNOLOGY

(Rajasthan Technical University, Kota)

IN

COMPUTER SCIENCE ENGINEERING

SESSION (2011-2012)

SUBMITTED TO: SUBMITTED

BY:

Mr. S.S Agarwal Neha

Khandelwal

HOD, CE Dept. CSE, VII

Semester

08EEMCS301

GOVT.MAHILA ENGINEERING COLLEGE AJMER

NASIRABAD ROAD, MAKHUPURA, AJMER-305002

AKNOWLEDGEMENT

This is opportunity to express my heartfelt words for the people who were part of

this training in numerous ways, people who gave me unending support right from

beginning of the training.

I am grateful to training incharge Mr.…………………… for giving guidelines to

make the project successful.

I want to give sincere thanks to the principal, Prof. M.C. Govil for his valuable

support.

I extend my thanks to Mr. S.S Agarwal, Head of the Department for his

cooperation and guidance.

Yours Sincerely,

Neha Khandelwal

ABSTRACT

TABLE OF CONTENTS

1. INDIAN RAILWAY(Organizational Structure)

2. SIGNALING

NEED

TYPES OF SIGNALS

OVERLAP & ISOLATION

3. TRACK CIRCUITS

4. AXLE COUNTER

5. PRINCIPLE OF INTERLOCKING

6. RAILWAY SIGNALING DATALOGGER

7. TRAIN CHARTING

8. AUTOMATIC TRACKING OF TRAIN

9. COMPUTERISED PASSENGER RESERVATION SYSTEM(PRS)

10. IVRS

11.MICROWAVE COMMUNICATION

12.RAILNET

INDIAN RAILWAY

INTRODUCTION

India boasts of the world’s largest railway network in the world. Every day, millions of people

travel around in hundred of trains running between various stations smoothly and safely. Thanks

to then English people who laid the foundation for the Indian railway network, it is applauded

even today across the globe.

Organizational Structure:

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

Ministry of Railways. Indian Railways is administered by the Railway Board, which has a

financial commissioner, five members and a chairman.

Railway zones

The headquarters of the Indian Railways in New Delhi

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.

Sl. No

Name Abbr. Headquarters Divisions

1. Central CR MumbaiMumbai, Bhusawal, Pune, Solapur, Nagpur

2.East Central

ECR HajipurDanapur, Dhanbad, Mughalsarai, Samastipur, Sonpur

3.East Coast

ECoR BhubaneswarKhurda Road, Sambalpur, Visakhapatnam

4. Eastern ER KolkataHowrah, Sealdah, Asansol, Malda

5.North Central

NCR AllahabadAllahabad, Agra, Jhansi

6.North Eastern

NER GorakhpurIzzatnagar, Lucknow, Varanasi

7.North Western

NWR JaipurJaipur, Ajmer, Bikaner, Jodhpur

8.Northeast Frontier

NFR GuwahatiAlipurduar, Katihar, Lumding, Rangia, Tinsukia

9. Northern NR DelhiDelhi, Ambala, Firozpur, Lucknow, Moradabad

10.South Central

SCR Secunderabad

Secunderabad, Hyderabad, Guntakal, Guntur, Nanded, Vijayawada

11.South East Central

SECR Bilaspur, CGBilaspur, Raipur, Nagpur

12.South Eastern

SER KolkataAdra, Chakradharpur, Kharagpur, Ranchi

13.South Western

SWR HubliHubli, Bangalore, Mysore

14. Southern SR Chennai

Chennai, Madurai, Palakkad, Salem, Tiruchchirapalli, Thiruvanathapuram

15.West Central

WCR JabalpurJabalpur, Bhopal, Kota

16. Western WR Mumbai

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

The Kolkata Metro is owned and operated by Indian Railways, but is not a part of any of the

zones. It is administratively considered to have the status of a zonal railway.

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 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. 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.

SIGNALLING

NEED

All over the world Railway transportation is increasingly used, as this mode of transport is more

energy efficient and environmentally friendly than road transportation. Trains move on steel rail

tracks and wheels of the railway vehicle are also flanged Steel wheels. Hence least friction occurs

at the point of contact between the track & wheels.

Therefore trains carry more loads resulting in higher traffic capacity since trains move on specific

tracks called rails, their path is to be fully guided and there is no arrangement of steering. Clear

of obstruction as available with road transportation, so there is a need to provide control on the

movement of trains in the form of Railway signals which indicate to the drivers to stop or move

and also the speed at which they can pass a signal.

Since the load carried by the trains and the speed which the trains can attain are high, they need

more braking distance before coming to the stop from full speed. Without signal to be available on

the route to constantly guide the driver accidents will take place due to collisions.

There are basically two purposes achieved by railway signaling:

1. To safety receive and dispatch trains at a station.

2. To control the movements of trains from one station to another after ensuring that the track on

which this train will move to reach the next station is free from movement of another train either

in the same or opposite direction. This Control is called block working. Preventing the movement

from opposite direction is necessary in single line track as movements in both directions will be

on the same track.

Apart from meeting the basic requirement of necessary safety in train operation, modern railway

signaling plays an important role in determining the capacity of a section .The capacity decides

the number of trains that can run on a single day. By proper signaling the capacity can be

increased to a considerable extent without resorting to costlier alternatives.

The essential components of railway signaling:

The fixed signals provided by the side of the railway track with indication in the form of colour

lights are the actual authority to a driver to get in to the portion of the track beyond the signal. At

stations the trains may be received on any one of the platform lines. To take the train to any

specific track, points are provided. The purpose of the point on the track is to divert the train from

one track to adjacent one. Hence the signal has to be connected to the points in an arrangement

called interlocking. This Interlocking arrangement only ensures that a point is correctly set for the

particular route or a track and the signal conveys this information to the driver.

Trains run on dedicated line .A line consists of two rails running parallel to each other. This is

also called “Track”. The width of the track is 5‟6”in Broad gauge (B.G)

The track is represented in Signaling plans by a single line as shown below.

In station yards there will be more than one track for receiving and dispatching trains.

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

In both the above cases, when one switch rail is closed with its stock rail, the other switch is open.

In either case, the opening shall be 41/2”. Between the closed switch and its stock rail not more

than 1/8” gap, is permitted.

The centre to centre distance between the adjacent tracks (between main line to the adjacent loop

line or between one loop line and other adjacent loop line) shall not be less than 14”0’. Where

cross-over pints are provided between adjacent tracks, this distance gets reduced. At the place

where it is less than 14”, one track may foul the other track. At this point a ‟fouling Bar” (a

cement lab of about 5” length with inscription “FOULING MARK” is provided.

When a train drawn on a track, it should stand clear of the FOULING MARK as otherwise, the

train may foul the movement of train on the adjacent track, thereby causing a side-collision.

Clearance of track:

Since a train cannot be received on the portion of track where another train is standing on same

portion of the track, the signal before it is cleared for the movement of a train has to ensure the

track clearance. There are equipments used in Railway signaling to achieve the above safety

condition.

TYPES OF SIGNALS:

Signal:

Signal is a medium to convey a particular pre-determined meaning in non-verbal form.

Multiple Aspect Color Light Signal (MACLS):

Multiple means more than 2 indications .They may have 3 or 4 different aspects or indications to

be given to the driver. These signals have longer range of visibility and Improved reliability.

Classification of CLS:

Manual Stop Signal:

Each aspect of the signal is represented by a circle. A horizontal line inside the circle indicates

Red aspect, an inclined line the yellow aspect and vertical line the Green aspect. The normal

aspect of the signal is Red shown by double line.

Permissive Signal (Distant Signal):

Shall be located at an adequate distance in rear of the stop signal, the aspect of which it pre-

warns.

The normal aspect of permissive signal is “Single Yellow”

where 2 distant signals are provided to pre- warn the stop signal, the outer most signal, to be

located at an adequate distance from the first stop signal, shall be called the distant signal and the

other called the inner distant signal, with the distant capable of displaying “attention” or

“proceed” aspect only .

To distinguish between stop signal and permissive signal “P” marker board (letter in black on

white board) is fixed to the permissive signal.

The normal aspect of an automatic signal is green and is indicated by the double vertical line,

unlike the manual signal where the normal aspect is red and indicated by double horizontal lines.

An automatic signal has an “A” marker plate fixed to the signal post to distinguish it as an

automatic signal. Letter “A” in black on white circular disc.

Semi-automatic Stop Signal:

An illuminated “A” marker distinguishes a semi – automatic signal from a fully automatic signal.

Letter “A” against black back ground is illuminated when working as an automatic stop signal and

letter “A” extinguished when working as a manual stop signal.

Gate Signal:

The Gate stop signal shall be provided with „G‟ marker. Letter “G” in black on a yellow circular

disc.

A semi-automatic stop signal interlocked with a level-crossing gate shall be provided with “G”

marker disc and an illuminated “A” marker. The “A” marker shall be lit only when the gates are

closed and locked against road traffic.

Routing Indicator:

Where two are more lines diverge, information is to be given to driver that he is being received on

diverge line. Hence route indicators are provided.

Route indicators are fixed on the first stop signal and starters.

If the route indicator on a signal is not in working order, the relevant signal shall also to be treated

as defective signal.

Route indicator is denoted as (UG).

Route indicators are of three types.

Junction type route indicator:

Used where the speed is above 15KMPH

It is having a provision of indicating six diversions and a straight line.

When taken off it shows a row of five white lines.

Multi lamp route indicator:

Used where the speed is less than 15 KMPH.

It can exhibit nine numerals and alphabets.

Stencil type route indicator:

Normally fixed on starter signal

Subsidiary Signals: Signals are used for reception of trains in to a station and despatch of trains

out of station. Signals used for movement of trains within the station section at restricted speed

and for special purpose are called Subsidiary signals. In MACL signalling Shunt signals and

Calling–on signals come under subsidiary signals

It is of position light type, The lights shall be white in colour. Shunt signals control shunting

movements.

A shunt signal may be placed on a post by itself or below a stop signal other than the first stop

signal of a station.

When a shunt signal is taken “OFF”, it authorizes the driver to draw ahead with caution for

shunting purposes although stop signal, if any, above it is at “ON”.

When a shunt signal is placed below a stop signal, it shall show no light in the „ON‟ position.

A Calling-on signal has no independent location and displays no aspect in “ON” position. A

calling-on signal where provided, shall be fixed below a stop signal governing the approach of a

train with “C” marker board fixed to the signal post. A calling-on signal when taken “OFF” it

displays a miniature yellow light.

Under approved special instructions, a calling-on signal may be provided below any other stop

signal except the last stop signal.

When placed below a stop signal, it shall show no light in the “ON” position. A calling-on signal

under main signal above it cannot display “OFF” aspect at same time.

Markers & boards:

Warning Board: Provided to warn the driver that he is approaching a stop signal. To draw

attention of the driver in the night, self-reflecting sheets are fixed. It is located not less than 1.5

km in rear of FSS. Where double distant is provided, warning board is dispensed with.

Shunting Limit Board: Provided on single line sections where shunting in the face of

approaching train is permitted, Placed at a distance not less than 180 Mts. from the opposing First

stop signal.

Block Section Limit Board: Provided on double section where there are no facing points or the

outer most points at the approaching end are trailing. It shall be placed at a distance not less

than180 Mts. from the first stop signal.

Outlying Siding: Where an intermediate siding taking „OFF‟ in the facing direction in passenger

running line outside station limits is provided with „S‟ marker board to indicate that a siding is

taking „OFF‟ from main line.

CONCEPT OF OVERLAP AND ISOLATION

Every stop signal by its indication to the driver controls the movement of train upto the next stop

signal as the next stop signal will control the movement beyond it. Hence the track between the

stop signal and the next has to be clear and the points have to be correctly set and locked before a

movement is permitted by it. However due to any unforeseen reasons like with sudden brake

inadequacy the driver may not be able to stop at the next stop signal. So an extra safety margin of

the track beyond the next stop signal is also to be kept free so that if the train overshoots the next

signal, he will be able to bring the train to stop within that margin. This safety margin is called

“overlap”.

Similarly we have to ensure that when a train moves on the track the other rail vehicles from the

adjoining track should not roll down and infringe with the movement. To prevent this “isolation”

between adjoining lines is required.

OVERLAPS

Overlaps are referred to as ADEQUATE distance. Overlaps are of two types:

1) Block Over Lap (BOL)

2) Signal Over Lap (SOL)

Block over lap: It is the extra length of track in advance of the FSS (First Stop Signal) of a

station, which must be kept clear, before Line clear can be given to the station in rear.

BOL in MACLS sections shall not be less than 180 Mts.

Signal over lap: The length of track in advance of a stop signal of station, which must be kept

clear, before the signal next in rear could be taken „OFF‟.

SOL in MACLS sections shall not be less than 120 Mts.

In case of Automatic signals the adequate distance is 120 Mts. minimum.

ISOLATION

The term isolation denotes the condition in which line for a particular movement of a train is

separated from all adjoining lines connected to it in such a manner that it cannot be fouled or

interfered with by any movement taking place on the adjoining lines .

Rules regarding isolation:

A line, on which train movements at speeds higher than 50 KMPH are permitted, should be

isolated from all connected lines.

Passenger lines should be isolated from all connected goods lines and sidings, whatever the

speed may be.

Isolation of goods reception lines from sidings is considered desirable.

To maintain safety in through running, points and trap sidings should be not be inserted in the

main or through line except with the permission of CRS.

Where other means cannot be adopted to permit simultaneous reception on a single line.

To trap vehicles running away from a station.

To avoid trains entering from block section due to heavy falling gradient

Methods of Isolation:

1) Connecting to another line or a siding.

2) Provision of short dead end siding

(Vehicles not to be stabled on siding)

3) Provision of traps derailing switches

4) Provision of double derailing switch with lead rails without crossing.

5) Long dead end siding with trap (vehicles can be stabled on this siding).

6) Provision of sand humps.

Slip Siding & Catch Siding:

On Indian Railways for all gauges the maximum gradient permitted is 1:400, where as1:1200 is

usually allowed within the station yard. No station yard should be steeper than 1:260, except due

to geographic conditions. Where such gradient cannot be avoided with in the station yard, condo

nation of CRS is to be to be obtained for providing „SLIP SIDING„. Slip siding will prevent

vehicles entering block section.

Where gradients are steeper than 1:80 falling towards the station, to prevent vehicles entering

station section from block section. This arrangements is known as “CATCH SIDING” Catch

siding will prevent vehicles entry into block section.

Slip sidings and “Catch sidings” points must be interlocked with block instruments and these

sidings should not be used for shunting or stabling purposes.

Location of Signals

Home Signal: On single line, shall be placed at not less than 300 Mts. in rear of the first facing

point. On double line may be located at a distance of not less than 180 Mts. in rear of the facing

points or BSLB.

Distant Signal: On single line or double line shall be placed at an adequate distance of normal

braking distance which shall not be less than 1 KM from the stop signal. If the second distant is

used, the inner distant is to be 1 KM in rear of home signal (first stop signal) and outer distant is

to be 1 KM in rear of inner distant.

Routing Signal: Shall be placed just in rear of the facing points to it protects.

Starter Signal: Placed in rear of the facing point or fouling mark of the converging lines such that

they should protect the adjacent running line.

Advanced Starter: Shall be placed outside all the connections on the line to which it applies, and

shall not be less than 120 Mts. from the outer most point on single line. On double line this

distance is from the starter signal and in special case upto a distance of full train length beyond

outer most point where frequent shunting is involved the main line.

FIG. MARKERS PROVIDED ON SIGNAL POSTS

Fig. METHODS OF ISOLATION

TRACK CIRCUITS

Track circuit is a vehicle detection device in which the running rails form part of an electrical

circuit. The boundaries of track circuit are marked by insulation joints on the rail and rails are

bonded at rail joints for better conductivity.

Uses of Track Circuits:

For detecting the presence of vehicles or absence of vehicles within the limits of the track

circuits.

For locking the point when train is on the point.

Trolley protection circuit for axle counter to ensure wheels of easily removable trolleys are

not counted.

Closed TC: In this type current is always flowing through the relay. When train comes over the

track, the supply to the relay is shunted and the relay de-energizes.

The smallest closed track circuit provided is of 26 meter length. The longest workable track

circuit depends on the Ballast Resistance (i.e., Resistance across rails offered by the stone chips

placed below the rail to support track), This ballast decides the leakage current. In other words

ballast resistance appears across or in parallel with relay coil resistance.

Open Track Circuit:

Open track circuit is one in which the track relay is normally de-energized and picks up only when

train comes on the track.

In this track circuit any disconnection with train on the track will drop the relay and failure on

unsafe side will take place, as the relay will show track is clear under occupation. Hence this track

circuit can be used for short length only i.e., 26 Mts. Now a days open track circuits are not used.

Fed over track circuit:

It is a sub division of track circuit. This is generally adopted when it is not possible to work a long

track due to inability to maintain prescribed parameters like ballast resistance for fail safe working

of track circuit.

Instead of dividing it in to independent track circuits, the first track circuit is fed by the usual

battery and relay arrangement. The feed to the second track is taken through the front contact of

the track relay which controls the first track and so on. The last track relay can serve to indicate

occupancy or clearance of the portions of all track circuits.

Triple pole lamps

Normally in the past signal lamps having 2 filaments as per following arrangement were used.

The 2 filaments are Main (12 V 25 Watts) and Auxiliary (rated for higher than 12 V and wattage

much less than 25W). Both filaments are in parallel connection by having the ends of the

filaments brought on same 2 terminals. That is why these lamps are known as 2-pole 2-filament

lamps. Due to the arrangement both filaments will glow together all the time. The hotspot that can

develop at the place where they are close to each other is a source for fusing .If due to a higher

voltage main filament may fuse, but auxiliary may not fuse due to its higher voltage rating, But

output of auxiliary is less and lamp will be dim

To overcome the above, CLS Triple lamps are nowadays used. There are two filaments of equal

voltage and wattage. One filament (main) is lit normally and the second filament (auxiliary) is

switched ON when main filament fuses.

Since both the filaments have same ratings and lumen output, the visibility of the CLS is not

affected the two filament are provided in parallel configuration to avoid possibilities of hot- spot

formation. One terminal of both filaments is common. While the other terminal is independent

and hence 3 poles are used

AXLE COUNTER

Comparison with track circuit

To detect the presence of vehicle within a prescribed distance is the role of track circuit.

Dropping of track relay is due to shorting of rails by the axles of a vehicle train.

Disadvantages of track circuits:

Either wooden or P.S.C. sleepers needed.

Influence of B.R. and T.S.R. values (with weather).

Controlled section length is limited.

Insulation joints are compulsory or special type of track circuit is needed for joint less

working.

More maintenance due to varying track parameters.

Features of Axle counter:

It works on magnetic flux variation on a ground device for counting the axles and electronic

circuits to evaluate in-count and out-count. To detect the presence of wheel.

Advantages of using axle counter:

It does not require wooden or PSC sleepers.

It can cover very long sections up to 15 kms.

It does not get affected either by flooding or poor maintenance of track. It does not require

insulation joints and so the track can be long welded.

Application of axle counter:

Monitoring of berthing tracks.

Monitoring point zone tracks.

For automatic signaling system.

For Intermediate block signaling.

Level crossing warning system.

Proving block section clearance.

At steel bridges in lieu of track circuits.

Various types of axle counter:

1. Analog axle counter (amplitude modulation),

2. Digital axle counter (phase modulation).

Analog axle counter:

1. Single entry-exit system (max. 2-D),

2. Multi entry-exit system (max. 4-D) (D = detection point)

Each detection point consists of a pair of TX/RX units.

1-D SYSTEM: common detection point for berthing tracks on terminal yards.

2-D SYSTEM: berthing tracks, block sections, etc.

3-D SYSTEM: points, crossings, sidings, etc.

4-D SYSTEM: points, sidings, crossings and branch lines, etc.

Operating Principle of Axle Counter

The tack equipment consists of 4 sets transducers (transmitter and receiver) fitted to the track at

each detection point, The two sets at each end (detection point) fixed on same rail are staggered to

discriminate the direction of traffic.

When power is given to Tx coil the magnetic flux is produced and it links with the Rx coil. The

Tx and Rx coils are placed face to face. It produces a voltage in the Rx coil. When the wheel of

train passes in between Tx and Rx coil, the magnetic flux linking them is cut and the voltage in

Rx coil drops. This change in the level Rx coil is sensed as an amplitude or phase change.

Depending upon the particular design, the out put of all the Rx coils (2 frome one end of Axle

counter section and 2 from the other end of Axle counter section) are taken to the evaluator

located in the station, through Quad cable.

Then the ‟IN” count and “OUT” count are derived from the field equipment and evaluated for

comparison. If the in count and out count are equal the evaluator shows “SECTION CLEAR”. If

there is any discrepancy in the two counts, (it means some wagons / compartments are left in the

section) and therefore the evaluator shows “SECTION OCCUPIED”.

At the same detection point , if some axles enter into the section and then return, the system will

show “SECTION CLEAR” , if the in and out count are equal .

Trolley-suppression Track circuit:

If a non- insulated push- trolley enters the track detections unit, the two axles will be stored as 2 in

counts. The evaluator will show section occupied. The push-trolley can be physically lifted off the

track and kept aside. Even though the section is clear the system will show section occupied. To

avoid this, a short two rail length closed track circuit is provided at each diction point and the

transducer equipment of the axle counter is fitted within the track circuit.

Only insulated push-trolleys are to be used, When the insulated push-trolley passes over the track

relay will not drop. In which case, the evaluator will not register the counts . On the other hand, if

a train axles passes, it shunts the track and the track relay de-energizes before the axles passes

over the transducers in which case the evaluator will register the count.

PRINCIPLES OF INTERLOCKING

Interlocking : Means an arrangement of signals , points and other appliances, operated from a

panel or from lever frame, so interconnected by mechanical locking or electrical locking or both

that their operation must take place in proper sequence to ensure safety.

Essentials of Interlocking:

It shall not be possible to take “OFF” a running signal, unless all points including isolation are

correctly set all facing points are locked and all interlocked level crossing gates are closed and

locked against road traffic for the line on which the train will travel, including the overlap.

After the signal has been taken “OFF” it shall not be possible to move any points or lock on the

route including overlap and isolation, nor to release any interlocked LC gate until the signal is

replaced to the “ON” position.

It shall not be possible to take “OFF” at the same time any two fixed signals which can lead to any

conflicting movements and where feasible points shall be so interlocked as to avoid any

conflicting movement.

Electrical Lockings:

Route locking:

After a route is set (that is, the points in the route are operated to the position as required for the

route), it is electrically locked before the signal is cleared. By this we mean the points in the route

are electrically locked and they cannot be operated for any other route till such time the route that

is locked is released and the points become free for operation.

Route molding:

Once a route is set, locked and the signal is cleared for a train, it must be held till such time the

train is received on the berthing track or the route is released by an emergency route release

operation.

Track locking:

It is an electrical locking on a point which prevents the operation of the point when a train

occupies the track circuit provided over the point.

When a train is on 51 AT or 51BT, the respective track relay will be de-energized. Under this condition, it

is not possible to operate the point either by route initiation or by individual operation. We say the point is

track locked.

Indication locking:

It is an electrical locking so provided as to ensure that after the reception of the train on the

berthing track the route is not released unless it is proved that the signal which was cleared for

receiving the train has gone back to danger and all the signal control relays have de-energized.

Approach locking:

It is an electrical locking effective while a train is approaching a cleared signal and adopted to

prevent releasing of the route when the train is within a “Pre-determined distance” from the

signal.

For the purpose of providing approach locking on the signal, a track circuit called “Approach

Track” (AT) needs to be provided to a length of 1-2 kms. (Braking distance of 1km + reaction

distance of 200mts.) in rear of the signal as shown below

Case I: Train is beyond the pre-determined distance

Assume that the home signal is displaying the yellow aspect. The distant signal displays the green

aspect. The train is beyond the pre-determined distance as shown above. And the driver has

accepted the signal aspect.

If now the home signal is thrown back to danger (Red), the distant signal automatically changed

its aspect from green to yellow. The driver of the approaching train on seeing the change of aspect

in the distant signal will react, apply the brake and bring the train to a stop at the foot of the home

signal. Therefore, immediately after throwing the home signal back to danger, the route can be

released. The approach locking is not effective in this case and there is nothing unsafe also as the

train is going to stop at the home signal.

Case II: Train is Within the pre-determined distance

In this case, we assume that the train has come within the pre-determined distance at the time of

throwing the signal back to danger. The approach track is occupied. The driver on seeing the

change of aspect in the home signal to Red, immediately applies the brake. But, he may not be

able to bring the train to a stop at the signal as the braking distance is not available. He may

overshoot the signal. It is not safe to release the route. The approach locking becomes effective in

this case and the route cannot be released.

Case III: Approach locking with time release.

Let us assume a condition when, at the time of throwing the home signal back to Red, the train has

just come within the approach track. Approach locking is effective and the route cannot be

released. But, the driver is able to control the train and brings it to a stop. Now, it must be possible

to release the route. Provided it is ensured that the train has stopped at the foot of the signal. Even

though AT is occupied.But, how to ensure that the train has stopped? A physical verification is

not possible. We depend upon a time factor to ensure this.

After putting back the signal to operator, the route release is attempted by the SM/Panel operator.

The route will not be released; but a time-element relay will be switched on. After a time delay of

2 minutes, the route will be released automatically. Now, the route can be altered signal cleared

and the train can be received on the altered route.

But, if the driver is not in a position to stop the train, he will pass the signal at Red. Once the train

has passed the signal, the back or route locking becomes effective and the route cannot be

released. The train has to be received on the route which is already set.

Dead approach locking:

It is seen that for providing approach locking, a track circuit for a length of 1,2kms. Need to be

provided. Provision of such a long track circuit for the purpose of approach locking is a costly

proposition. Therefore, the approach locking is provided without the approach locking becomes

effective the moment the signal is cleared irrespective of the position of the train in the approach.

Such an approach locking is known as “Dead approach locking”. In other words, once the signal

is „OFF‟ it gets approach locked and the route can be released (after putting back the signal to

danger) only after a time delay of 2 minutes.

Back locking or route locking:

It is an electrical locking effective when a train has passed the signal and adopted to prevent

releasing of the route while the train is “within the limits of the route entered”.

For any signal, the route is from the foot of the signal up to the next signal ahead. But, the limits

of the route are from the foot of the signal up to and including the last point in the route. for

example, for the home signal or the calling-on signal below it, the limits of the route for the

purpose of back locking is from the signal up to the berthing track. The berthing track circuit shall

not be included in the back locking.

For S10 and C10, the back locking track circuits are 10T, 10T1, 56BT and 54T for both the routes

10A and 10B. So long as the train is moving over these track circuits the back locking will be

effective and route cannot be released. After the train clears 54T the route will be released

automatically.

For S3 and shunt 103, the back locking track circuits are 3T and 56AT.

RAILWAY SIGNALLING DATALOGGER

Introduction to Data Loggers

Technically speaking, a data logger is any device that can be used to store data. This includes

many data acquisition devices such as plug-in boards or serial communication systems which use

a computer as a real time data recording system. However, most instrument manufacturers

consider a data logger a standalone device that can read various types of electrical signals and

store the data in internal memory for later download to a computer.

The advantage of data loggers is that they can operate independently of a computer, unlike many

other types of data acquisition devices. Data loggers are available in various shapes and sizes. The

range includes simple economical single channel fixed function loggers to more powerful

programmable devices capable of handling hundreds of inputs. Data logging is now a standard

technique within railway signaling engineering for both safety and performance management

purposes. However, many of the systems currently in use are based on old technology and whilst

beneficial, do not offer the functionality and cost benefits that the industry requires for the future.

The SA380 has been developed specifically to meet these requirements. Specified functionally by

signal engineers it is the ideal solution for level crossing, interlocking and bespoke monitoring

applications.

Simplicity

All data acquisition cards and associated electronics are contained within one enclosure, resulting

in a compact yet modular solution. The number of channels per installation is configurable

depending on customer / site requirements.

Networking and data access

The SA380 is enabled with the global networking standard TCP/IP and features a built in web

server. It can be remotely accessed over Ethernet or a dial-up link.

Data storage

The SA380 uses a simple RAID system, duplicating data to both its internal storage and a

removable Compact Flash card. This duplication enables the Compact Flash card to be removed

and used in incident investigations without affecting data stored on the logger.

Cost savings

The deployment of the SA380 is the most cost-effective data logging solution, from level crossing

to major interlocking schemes. Key savings are offered from:

Ease of installation

Low maintenance

Integration of UPS, modem, display and input cards

At the most compact end, a 48 or 96 channel unit will monitor a level crossing. For larger

installations up to 8 units can be connected together, enabling 3072 channels to be monitored

simultaneously. All systems use the same common platform resulting in economies of production.

Recorded data can be accessed using a standard web browser. For advanced remote analysis and

diagnostic features (such as slow moving point alarms or SPAD investigations), a software plug-

in has been developed for the Balfour Beatty Rail Asset View system.

In addition, the SA380 has a touch screen LCD to allow maintenance technicians to access data

directly on site. This removes the need for an inconvenient laptop computer or separate handheld

terminal.

Reliability

Contained within the unit is a fully functional Uninterruptible Power Supply giving six hours of

battery backup in the case of mains failure.

Low power consumption means that no cooling fan is required, which in turn means there are no

dust filters to clean or moving mechanical parts to fail. If maintenance is required, the entire unit

can be removed simply by disconnecting the input leads and a mains plug.

Safety

The SA380 has been designed specifically to meet the stringent safety requirements of railway

signaling applications. All digital and analog input channels are opto isolated to a minimum of

1kV.

Usability

The SA380 is easy to install and use, with all functionality integrated into one compact unit.

A breakout board is available to enable simple connection to signaling relays. It is designed to fit

the standard bars found in relay rooms and location cases.

Both the logger and its configuration software have been designed with ease of use as top priority.

The unit will begin logging straight out of the box as soon as it is switched on.

DATALOGGER BASED COMPUTERISED TRAINCHARTING

INTRODUCTION:

All the stations on Nagda-Kota-Gangapurcity-Mathura route of Kota Division are equipped with

data loggers. Data loggers are networked as per control sections. In Kota-Gangapurcity section 23

stations are provided with 25 data loggers. Since the information of the vital relays is available at

Control Office i.e. Kota. It is possible to track a train and to chart the train movement

automatically. The system is not only track the train but also predict the train movement for the

next few hours, which is equivalent to the manual planning by the ATNL. Based on the train

information & charting data various statistics can be generated in the form of reports which are

time consuming & tedious if done manually.

Section No of Data loggers

Kota - Nagda 29

Kota - Gangapurcity 25

Gangapurcity - Mathura 18

SETUP:

Entire Rajdhani route of KOTA division (having 62stations, 549Kms) have been provided

with Networked Data loggers.

All the Data loggers are connected through existing RE telecom cable in series to FEP. The FEP

of the Data logger Network is connected to the Servers through a computer containing NMDL

software with Train charting logics. (See Fig: 1-System Configuration) The client software is

provided for viewing the chart / data. This client software by default is a passive client (which

doesn’t enable chart editing & manual entry) but on accessing into higher levels by issuing

passwords it acts as an active client (which enables chart editing & manual entry provisions).

Active Client maintained by ATNL who has the control over the train movements and is

connected to the server through LAN. At any time, active Client can control the train movement

charting. Active Client can feed the Train information as shown in

Passive Clients to view the chart anywhere from the network, the chart available at this client is

unchanged and cannot be modified. Any number of passive clients can view the train chart by

connecting to the server. In short, the chart is available to all users using client end software by

logging on the server through LAN / Modem (Dialup or leased) / Microwave / Intranet / Internet .

Fig: 1- System Configuration

AUTOMATIC TRACKING OF TRAIN

For tracking a train movement, basic concept of sequential operation of track circuit is monitored

along with the position of points en-route. For this purpose all Exit/Entry routes are tabulated in

terms of Geographical position of Track circuits & point position, station wise.

Whenever any T.C. is dropped it activates the route, which contains that track circuit. As the train

moves, track circuits will drop sequentially & finally only one unique route will be selected. At

this stage this train will be allotted train index Automatically for further identification of the train.

With the point position and the berthing track position it can be determined that at what line /

platform the train is received. Similarly when the train leaves the station, it will select the

appropriate exit route. When this train touches the Home Signal track of next station it checks if

prior to this AZTR of Block section in rear & the Advance Starter track of previous station were

dropped. This is co-related the station-to-station train charting. Since the train index is carry

forward in this process, it is therefore possible to plot the correct train.

The train charting software facilitates the ATNL to enter the train No., and other train information

such as Loco / Engine No., Driver’s name, load, Guard’s name, vacuum, etc. This software also

facilitates to edit the train charting whenever necessary. It allows making links if joints in auto

mode. It allows charting manually even if Automatic charting is partially or totally failed. For the

convenience of ATNL two monitors are provided. One screen always shows the chart and another

is used to open the manual-charting string grid or to pop-up other forms.

Features:

Auto tracking of train on real time.

Online Plotting of chart.

Charting of train from starting to destination point.

Alarm generation & tracking of any new train entered in the section automatically.

Reporting of deviation from scheduled timings.

ATNL can write abbreviated codes on the chart, as he writes in Manual Charting.

This can be taken automatically to unusual entry.

Hard copy of chart for online or offline data. User can get as many as copy required.

Adjustable color scheme for plotting and display of train movement on the chart.

Provision for train information entry for Train number, name, crew etc details.

Monitoring of maintenance blocks & displaying on the chart.

Enable crew changing point to effectively order train / Engine crews.

Forecasting of train movements.

Presentation of train number, location, its arrival / departure, on hold, predefined reason for

its abnormal status, etc.

In case of communication failures, provision for manual entry of train movement is possible.

Position of train and Engine for the last 8 hours can be seen in tabulated form with Crew

Detail.

Capable of displaying train position on Web.

ATNL Can observe status of all Line all stations on line.

Details of Yard position, Speed restriction and stable loads are displayed on Chart itself.

Super imposed Master chart also available with current chart and also available in tabular

form.

Software automatically considers Blocks & Caution orders for prediction.

Train Information automatically transfers to next control section. Need not to enter again.

ATNL can monitors the Average speed in block sections.

Different type of reports is readily available like – TOR, LTM, Punctuality, and Unusual etc.

Useful tools are available – Link, Delink, Draw blocks & Line with UNDO, Comments on

Graph, Highlighting train, Searching train etc.

Reminder of Block completion by Blinking.

Possible to put Comments on graph and also directly recorded in unusual.

Schedule timings of the passenger train can be seen in tabular form.

Earlier at the time of Chart changing controller has to redraw and rewrite all the information

available on outgoing chart to incoming chart. But now it is not required at all because it is

continuous screen.

User can select maximum 14hrs chart (7hrs of current chart + 7hrs of prediction).

Transparent Control system. Anyone can monitor control chart in control office on LAN.

ADVANTAGE THROUGH DATALOGGER BASED TRAINCHARTING:

Controller can devote more time on planning

Plotting is on Real time. No human involvement to plot the train so more accurate.

Online loop occupancy position

LIMITATIONS OF AUTOMATIC TRAIN CHARTING SYSTEM:

Networking communication media should work perfectly to maintain on-line status.

All the stations of the control section should be equipped with Data logger.

Train controllers should have basic computer knowledge.

Continuous track circuiting required.

COPUTERIZED PASSENGER RESERVATION SYSTEM OF THE INDIAN

RAILWAYS

INTRODUCTION:

The Indian Railways (IR)carries about 5.5 lakh passengers in Reservation reserved

accommodation every day.

The computerized Passenger Reservation System (PRS) facilitates booking and

Cancelling of tickets from any of the 4000Terminals(i.e. PRS booking windows)all over the

country.

These tickets can be booked or cancelled for journeys commencing in any party of India and

ending in any other part ,with travels times as long as 72 hour and distances up to several

thousands kilometre.

There are mainly four servers in INDIA. These are New Delhi , Kolkata, Channai, Mumbai &

sikandrabad.

EQUIPMENTS:

The equipment used in PRS are

Modem

Multiplexing Equipment

End terminal.

MODEM

Modem are used for communication various computer or between Computer & terminals over

ordinary or leased(dedicated ) telephone lines. We can use modems to log on to micro, mini,

main frame computer for line processing. We can use them to connect two remote computers for

data.

How does modem work?

The word modem in feed is derived from the words modulate & demodulator. Computer

communicate in digital languages while telephone lines communicate in analog language. So an

inter mediator required which can communicate both these language & hence MODEM plays

important role here.

Modem transmits information between computer bit by one 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 the modem change these characteristics determines the transmission speed of

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

The bound rate of modem is bits per second .In advance modulation such as quadrature amplitude

modulate 4 bits & transmitted it in each band. Thus the speed of the modem transmitting at 600

band would be 2400 bps. The modems can transmit data in two formats: Asynchronous &

Synchronous.

For critical application users may sometimes lease a second lines & keep it as a stand by link. If

the main link fails, personnel at both ends of the circuits switch the user equipments (multiplex &

router)to the stands by link. The analog modem switch at each location is connected to analog

modems of the main as well as the stand by links. If the main links fails, the switch units at either

end switch the user equipment at the stand by link. When the main links get restored, the analog

modem switches the user equipment back to main link.

Multiplexing Equipment:

There are two type multiplexing equipments for each channel. The multiplexer used may be of 8-

ports or 16-port .The data is get multiplexed at the rate of the 96KBps. The multiplexing

generally of analog type.

End Terminal

The end terminals of system is the station where the tickets to be Printed out .The terminal

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

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

IVRS (Interactive voice response system)

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 every 15 minutes duration.

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

with data entry computer called IVRS COMPUTER, which is 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.

HARDWARE

DATA ENTRY TERMINAL

It is a personal computer of more than 166 MHz with 16 MB RAM; 2.1 GB Hard disk; 101 key

keyboard; a mouse & a colour monitor.

MODEM

The data entry terminals are linked with lease line/ dialup modem of speed better than 33.6 KBPS.

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.

SOFTWARE:

There are three types of software.

COPETS

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

files.

This software is having following facilities,

(1) The system is secured by 3 stages of 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.

(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.

In IVRS system Mumbai Central computer acts as HUB and it will dial or connect through lease

line after a specific interval to the data entry computers of different control offices and exchange

the files with them.

When a pop file is generated after every 15 minutes in data entry computer, then file is

transferred to its queue directory. When HUB computer is connected to data entry computer, HUB

searches the files from queue directory and then down load in its receive directory and similarly

the queue directory files available in HUB will be received and stored by data entry computer. By

this way the queue directory files are exchanged and updated.

The communication software is also having the facility for CRC check (cyclic redundancy

check) and receive check. So in case of line failure or modem faulty, when the file could not be

exchanged, then HUB try to establish the link and if is not able to exchange, then it will create

alarm; and show link break

The important facilities of communication software: -

1) Auto dialing facility for origination of 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 of transfer of file as per priority decided by HUB.

5) It has facility to support WAN and is capable of interfacing with any type of communication

system like Internet, VHF; UHF, leased line.

6) Facility of monitoring of trans. and receive file.

7) It is provided with the list of transmitted files and remaining files.

OLTRIS SOFTWARE

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

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

accident of train; abnormal delay/late of the train and so on. So the software is developed to

support all the abnormal activity.

This software is having the following facilities:

a) It is having the facility to interact with both pulse and tone users.

b) It is having a facility of FAX on demand, for that separate terminal is provided.

c) It is supporting and select more than one language.

d) According to traffic, ports can be increased or decreased.

e) It is having the facility of mailbox.

f) It is having the facility of according the calls on each port and give a report of no. of calls in

24 hours and the calls in a specific period.

Overhead lines or overhead wires are used to transmit electrical energy to trams, trolley,

buses or trains at a distance from the energy supply point. In this article the generic term overhead

lineis used Overhead line is designed on the principle of one or more overhead wires situated over

rail tracks, raised to a high electrical potential by connection to feeder stations at regular intervals.

The feeder stations are usually fed from a high-voltage electrical grid.

MICROWAVE COMMUNICATION

INTRODUCTION

The objective of microwave communication systems is to transmit information from one place to

another without interruption, and clear reproduction at the receiver. Fig. indicates how this is

achieved in its simplest form.

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.

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.

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.

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. The data signals are received, amplified, and re-transmitted

by each of these stations.

Microwave Transmitter and Receiver

Fig. below 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.

why does mA signal preferred for signal transmission?

Current does not have any drop during transimission through electrical wires however the voltage

drops as the lengh of elecrical wire used for transmission increases. That’s why mA is preferred

over mV etc.

RAILNET

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 & 46 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 (IRCOT).

ORGANIZATION

First Rail-Net was established between RAILWAY BOARD, 9 Zones, and 6 production units

in phase 1.

Than extended to 6 new zones, 5 centralized training institutes, research and development

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.

RAILNET COMPRISES

1. Intra-net

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

communicate on this digitized network .

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.

TOOLS

o E-Mail

o EDI (Electronic Data Interchange)

o WWW

o FTP (File Transfer Protocol)

o TCP (Transmission Control Protocol)

OBJECTIVES

Railnet is used to provide following services :

Creation of Web pages.

E-mail.

Electronic transfer of data used for monitoring and coordination purpose.

Voice-over IP.

Video-conferencing .

Web-based application software development

Fax services.

Web surfing (Browser usage for internet and intranet).

HARDWARE COMPONENTS

‘Compaq’ Servers.

‘CISCO’ Routers, Switches & Hubs.

Structured cabling using UTP-Cat 5 cabling (10 MBPS) (Maximum distance permissible 100

meters between )

SOFTWARE COMPONENTS

MS Windows NT Server

Operating system for server

MS Windows NT Workstation 4.0

Operating system for workstations

Internet Information Server 3.0

Administrates internet access in LAN.

Front Page Express 98

For designing of web pages.

Lotus Nodes Clients 4.6

Provides E-mail facility to local users.

Cisco Works with SNMPC

Administrates router.

Cisco Pix Firewall

Provides safety to railway information.

NMS

Administrates FOIS.

HOW DOES RAILNET WORK?

Railnet 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

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

Various hubs can be connected in a cascade to increase the no. of terminations. This is a star

topology. Hubs along with computers within the distance of 50 meter are terminated on the

switch. In this manner all the computers in the LAN can share the data and can access the internet

through server.

Router also provides the facility of Dial Up Networking . It can accommodate 8 dial tone modems

which provide internet facility on distant computers.

Figure 1.1 Railnet Genral Arrangment

RAILNET NETWORK COMPONENTS

SERVER

A network is a multiuser system because more than one person at a time can send requests to a

machine. A shared machine together with the software programs , which handles requests and

distributes the network resources such as data files and printer time both the machine and its

software are jointly referred as the server.

Server has following characteristics:

1) Hardware including motherboard of the server is entirely different from a normal P.C.

2) It can be used with two processors of 500MHz.

3) It contains 3 hard disks having capacity of 9GB.These are connected to the motherboard

through RAD controller card .

4) A server should be able to implement security for its data.

5) It contains Microsoft Back Office Server 4.01 software which comprises following programs:

a) Microsoft NT.

b) Microsoft BackOffice.

c) Site Management Server.

d) Proxy Software.

e) Service Network Administrator

f) Exchange Server.

ROUTER

A router translates information from one network to another; it is similar to a super intelligent

bridge. Routers select the best path to route a message, based on the destination address and

origin. The router can direct traffic to prevent head-on collisions, and is smart enough to know

when to direct traffic along back roads and shortcuts.

Routers know the addresses of computers, bridges, and other routers on each side of the

network. Routers can even "listen" to the entire network to determine which sections are busiest,

they can then redirect data around those sections until they clear up.

Routers can:

Direct signal traffic efficiently.

Route messages between any two protocols.

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

Route messages across fiber optics, coaxial, and twisted pair cabling.

SWITCH

The switch is used to interconnect the Nodes. But it is more complex and versatile, and also there

is no division of bandwidth among the nodes.

They are active device with following points :

(1) 10Mbps, 100 Mbps, single-speed, or dual speed operation.

(2) Congestion control, which means that the switch should have enough buffers to take care of

the traffic peaks.

(3) Segmentation of local network

(4) Speed up the local network. They are of 8,16 or 48 ports active terminal.

FIREWALL

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

could not temper the information. The user can read the information but can not write anything.

HUB

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

cable (UTP, Coaxial etc). It contains a division of network bandwidth.

The important parameters to be considered whole selecting are: -

Support for dual-speed operations.

Number and types of ports, UTP and BNC.

Auto switching.

Support a built-in segment switch.

Ease of configuration.

It can have a capacity of 8, 16 or 24 nodes and the maximum distance between Hub and nodes is

100 Mt. If distance is more, then additional HUB must be used (but not more than 3).

NODES

The terminals or computers which are interconnected through switch or hubs, are called Nodes.

NETWORK INTERFACE CARD

It is a device having intelligence to control access to the network and enables communication

across the network. Through NIC the nodes are connected functionally and physically to the

network. It is also called network adapter.

In a LAN each device is attached to the shared transmission medium through a network interface

card (NIC).It contains logic for accessing the LAN and for sending and receiving blocks of data

on the LAN.