COMPANY PROFILE

1)Indian railways is the state owned railway company of India,which owns and operates the country’s rail transport.2)The Railways is divided into zones,which is sub-divided into divisions.3)There are total 16 zones,and each zone is headed by a GM who reports directly to the Railway Board.4)The zones are further divided into divisions headed by DRM’s.

5)The East central Railway is one of the

16 Railway zones.6)It is headquartered at Hajipur and

comprises of Sonpur,Samastipur,Danapur,Mugalsarai and Dhanbad divisions.

7)This zone came into existence on 8th September,1996.

INTRODUCTIONSignalling is one of the most important aspects of

Railway Communication.In the early days there was no fixed system of

signalling.Earlier systems used Time Interval Technique.In the Mid 19th century Mechanical Interlocking

came into existence.However,the most modern development in signal

interlocking is SSI.It’s first trial installation was provided at

Srirangam station in 1987.

SOLID STATE INTERLOCKINGTrain drivers know little of the overall topology of the

network through which they pass.

Safety is therefore invested in the Control system,or Interlocking.

The interlocking has to be designed to protect the operator from inadvertently sending trains along conflicting routes.

However, the network can be operated with more security if the operators have a broad overview about the distribution of trains,so a control panel displays the current status of signals,distribution of trains and other signalling equipment.

OPERATION OF SOLID STATE INTERLOCKING

There are seven main signals shown here,and three sets of points.

The operator can select a route by pressing the button at the entrance signal(say s7),then pressing the button at the exit signal-the consecutive main signal,being the entrance signal for the next route(s5).

This sequence of events is interpreted as a panel route request and is forwarded to the controlling computer for evaluation.

When the computer receives a panel request it evaluates the availability conditions.

These conditions are known as Geographic Data.If these conditions are met the system responds by highlighting

the track sections along the selected route on display.

At this point the route is said to be locked.Once the route is locked the interlocking will automatically

set the route.Firstly,this involves calling the points along the route into

correct alignment.Secondly,the route must be proved.This includes checking that the points are correctly

aligned,that the filaments in the signal lamps are drawing current,and that signals controlling conflicting routes are on(i.e red)

Finally,the entrance signal can be switched off.A driver approaching the signal will see it change from red

to green or yellow.

Thereafter,an indicator on the control panel will be illuminated to notify the operators.

The operation of SSI follows polling cycle.During this period the controlling computer

will exchange messages with each piece of signalling equipment to which it is attached.

Signalling equipment is interfaced with SSI through Track-side functional modules.

A points module will report whether the switch is detected normal or reverse.

Other than conveying status information about points and signals,TSR modules report the current positions of trains.

Track circuits are identified with the help of track sections.

If the low voltage applied across the rails can be detected,this indicates there is no train in the section

Atrain entering the section will short the circuit causing the voltage to drop and the track section will be recorded as occupied at the control centre.

OVERALL SYSTEM ARCHITECTURE

SSI is a multicomputer systemIt consists of two panel processors,a diagnostic

processor,and three central interlocking processors.The central interlocking processors are responsible for

executing all signalling commands and producing correct system outputs.

The panel processors are responsible for tasks which are not safety critical such as interfacing with the signal control panel,the display,and other systems.

The diagnostic processor is accessible from a maintainence terminal through which the system’s performance and fault status can be monitored.

The operation of SSI is organised around the concept of a major cycle.

During this period the central interlocking will address each of the TFM’s,and expect a reply from each in turn.

A maximun of 63 tfm’s can be connected to one SSI.The major cycle is divided into 64 minor cycles.In each minor cycle the central interlocking will

decode one incoming message(data telegram) from data highway,and process one outgoing command telegram.

The cable used is screened twisted pair.

GENERIC SSI SOFTWARESSI has been designed to be data driven with

a generic program operating on rules held in a “geographic database”.

The relationship between generic program and the data is one in which the former acts as an interpreter for the latter.

Due to this reason generic software is known as the control interpreter .

Motorola 6800 microprocessors used in SSI have a 16-bit address space.

60-80 kbytes are EPROM which hold the generic program,which is about 20 kbytes and the Geographic Data.

2 kbytes are RAM,and the rest is used for I/P and O/P devices.

The RAM is used to hold the system’s record of the state of railway-generally referred to as the image of railway or the internal state.

The SSI is organised on a cyclic basis with the major cycle determining the rate at which track side equipment receives fresh command.

The minor cycle performs all redundancy management,self-test and error recovery procedures.

The minor cycle has a minimum duration of 9.5 ms,and minimum major cycle time 0f 608 ms.

The initialization software compares the internal state of each of the three interlocking processors.

OPTICAL FIBRE COMMUNICATIONIn order to achieve a large information

capacity with a wide system bandwidth which can support a high data bit rate optical fibre came into being.

Since its advent optical fibres have increasingly replaced copper cables for LAN.

It is constructed of a transparent core made of nearly pure Sio2,through which light travels.

The core is surrounded by a cladding layer that reflects light,guiding the light along the core.

BASIC STRUCTURE OF OPTICAL FIBRE

A plastic coating covers the cladding to protect the glass surface.

An outer sheath of plastic or Teflon is used for protection.

There are two types of fibre-singlemode and multimode.

Singlemode is used for intercity cabling and highest speed,with a core diameter of less than 10 microns.

Multimode is used for short distances and has a core diameter of 50 to 100 microns.

OPERATION OF OPTICAL FIBRE

In an optical fibre, a refracted ray is one that is refracted from the core into the cladding.

For the fibre to guide the optical signal,the refractive index of the core must be slightly higher than that of the cladding.

The light in an optical-fibre cable travels through the core by constantly bouncing from the cladding following the principle of total internal reflection.

As the cladding does not absorb any light from the core,the light wave can travel can travel great distances.

FIBRE-OPTIC RELAY SYSTEMA fibre-optic relay system consists of-Transmitter-it receives and directs the optical device

to turn the light “on “ and “off” in correct sequence.Optical fibre-it conducts the light signals over a

distance.Optical Regenerator-it consists of optical fibres with

a special coating(doping).The doped portion is “pumped” with a laser.

When the degraded signal comes into the doped coating,the energy from the laser allows the doped molecules to become laser themselves.

The doped molecules then emit a new,stronger light signal with the same characteristics as the incoming weak light signal.

Thus,the regenerator is a laser amplifier for the incoming signal.

Optical Receiver-It takes the incoming digital light signals,decodes them and sends the electrical signal to the other user’s computer,tv or telephone.

The receiver uses a photocell or photodiode to detect the light.

APPLICATIONS OF OPTICAL FIBREFibres can be used as light guides in medical

and other applications.Can be used as sensors to measure

strain,temperature,pressure and other parameters.

Used in endoscopes to view objects through a small hole.

In some high-tech buildings,optical fibre are used to route sunlight from the roof to other parts of the building.

MICROWAVE COMMUNICATION

The international telecommunications system relies on microwave and satellite links for long-distance international calls.

The chief method of relaying long-distance calls on land is microwave radio transmission.

The drawback of long-distance voice communications via microwave radio transmission is that the transmissions follow a straight line from tower to tower,so that over the sea the system becomes impracticable.

The solution was proposed by Arthur C Clarke.

Thus geostationary satellites(syncoms) came into existence.

The first to be successfully launched,by Delta rocket from Cape Canaveral,was Syncoms 2 in July 1963.

Many such satellites are now in use concentrated over heavy traffic areas such as the Atlantic,Indian,Pacific oceans.

Telegraphy,telephony and television transmissions are carried simultaneously by high-frequency radio waves.

A GENERAL MICROWAVE SETUP

GENERATION OF MICROWAVE SIGNALSMicrowaves can be generated by a variety of

means,generally divided into two categories;Solid state devices and vacuum-tube based

devices.Solid state devices are based on

semiconductors such as silicon & include FET’s and BJT’s.

Vacuum tube devices operate on the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields and include magnetron,klystron,TWT and gyrotron.

USES OF MICROWAVE SIGNALSUsed for cooking food.Used in Radar.Wireless LAN protocols,such as Bluetooth

and the IEEE 802.11g specification also use microwaves in the 2.4 GHz ISM band.

Used in communication satellite transmissions because microwaves pass easily through the earth’s atmosphere with less interference than longer wavelengths.

NETWORKING SYSTEM OF RAILWAYSPRS-Passenger Reservation SystemThis is the full proof Reservation system used

by Railways.To facilitate hassle free reservation Indian

Railway has divided the entire network into 5 hubs-Secunderabad,New Delhi,Kolkata,Mumbai and Chennai.

UTS-Un-Reserved Ticketing SystemUTS is the complete solutin to provide

computerized unreserved tickets to railway passengers.

FOIS-Freight Operations Information System.CMS-Crew Management SystemIt is aimed at providing information

regarding the main line crew at all times.ICMS-Integrated Coach Management SystemCOAS-Control Office Application SystemIt is concerned with the controlling of train

movement.

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