indian railway 4

8/3/2019 Indian Railway 4

1/25

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.

I first of all take the opportunity to thankNORTH CENTRAL RAILWAYS (NCR) for

providing me this valuable opportunity to work and learn with them. During this trainingperiod everyone there had helped me in every possible way

they can.

I am also thankful to my parents, colleagues and DRM employees for their invaluable

support. A special note of thanks to Mr. Sanjay Nagar (Dy. CSTE/NCR), Mr. D. Goyal

(NCR) and many others for their help and suggestions.

MUDIT KHANLWAL


2/25

TABLE OF CONTENTS

Introduction

Module 1-Optical Fiber Communication

o Introductiono Optical Fiber Communication System

o Origin And Characteristics of Optical Fiber

o Operation of Optical Fiber

o A Fiber-Optic Relay System

o Application of Optical Fiber

o Advantages Of Optical Fiber

o Disadvantages of Optical Fiber

Module 2-Microwave Communication

o Introduction

o History of Telegraphic Signals

o Origin of Microwave Signals

o Microwave Communication Satellites

o Generation and Frequency Bands of Microwave Signals

o Microwave and Waveguides

o Uses of Microwave Signals

Module 3-Passenger Reservation System

o Introduction

o Equipment

o Use of IT in Indian Railway

Module 4-Local Area Networking


3/25

INDIAN RAILWAY

INTRODUCTION:-

Indian Railway is the state-owned railway company of India, which owns and operatesmost of the country's rail transport. It is overseen by the Ministry of Railways of the

Government of India.

India boasts one of the worlds largest railway network in the world. Every day, 20 millionpeople travel around the country in hundreds of trains running between various stations

smoothly and safely.

The formal inauguration ceremony of IR was performed on 16th April 1853with the first passenger train steamed out of Howrah station destined for Hooghly, a

distance of 36 km, on 15th August, 1854 .

Snapshots:-

It encompasses 6,909 stations over a total route length of more than 63,028

kilometres ofroute length and a track length of111,600 km

It is one of the world's largest commercial or utility employers, with more than 1.6million employees.

It grossed a revenue of 88,355 cr and The gross traffic receipts have registered agrowth of over 7.3% to 94840cr against 88356 cr

It moves

2 million tons of freight & 20 million people

daily across thecounty with the help of 200,000 (freight) wagons.

7,000 passenger trains across the country services20 million people totheirdestinations

Organisational Structure:-

IR 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.


4/25

MODULE 1

OPTICAL FIBER COMMUNICATION

INTRODUCTION

The demand for high-capacity long-haul telecommunication systems is

increasing at a steady rate, and is expected to accelerate in the nextdecade. At the same time, communication networks which cover long distances and

serve large areas with a large information capacity are also in increasing demand. To

satisfy the requirements on long distances, the communication channel must have a verylow loss. On the other hand, a large information capacity can only be achieved with a

wide system bandwidth which can support a high data bit rate (> Gbit/s) [3]. Reducing

the loss whilst increasing the bandwidth of the communication channels is therefore

essential for future telecommunications systems.

Of the many different communication channel available optical fiber proved to the most

promising due to its low attenuation, low losses and various other advantages overtwisted cables and other means of transmission.

Communication between stations and signalmen is done through telephone. In some

places, IR still uses twisted pair cables and elderly Stronger exchanges. This is currentlybeing upgraded to optical fiber and microwave communications. The main impetus for

this change came from the Department of Telecommunications, who no longer had the

expertise to maintain a large network of heritage technology. Drivers and guards wereequipped with VHF radio systems in 1999 to communicate with each other and with station

masters.


5/25

OPTICAL FIBER COMMUNICATION SYSTEM

A thin glass strand designed for light transmission. A single hair-thin fiber is capable oftransmitting trillions of bits per second. In addition to their huge transmission capacity,

optical fibers offer many advantages over electricity and copper wire. Light pulses are not

affected by random radiation in the environment, and their error rate is significantlylower. Fibers allow longer distances to be spanned before the signal has to be regenerated

by expensive "repeaters." Fibers are more secure, because taps in the line can be detected,

and lastly, fiber installation is streamlined due to their dramatically lower weight andsmaller size compared to copper cables.

Optical fiber v/s copper cables

The optical fiber acts as a low loss, wide bandwidth transmission channel. A lightsource is required to emit light signals, which are modulated by the signal data. To

enhance the performance of the system, a spectrally pure light source is required.

Advances in semiconductor laser technology, especially after the invention of doubleheterostructures (DH), resulted in stable, efficient, small-sized and compact

semiconductor laser diodes (SLDs). Using such coherent light sources increases the

bandwidth of the signal which can be transmitted in a simple intensity modulated (IM)system [13]. Other modulation methods, such as phase shift keying (PSK) and

frequency-shift keying (FSK), can also be used. These can be achieved either by directly

modulating the injection current to the SLD or by using an external electro or acoustooptic

modulator


6/25

ORIGIN AND CHARACTERISTICS OF OPTICAL FIBER

In the late 1970s and early 1980s, telephone companies began to use fibers extensively to

rebuild their communications infrastructure. According to KMI Corporation, specialists

in fiber optic market research, by the end of 1990 there were approximately eight millionmiles of fiber laid in the U.S. (this is miles of fiber, not miles of cable which can contain

many fibers). By the end of 2000, there were 80 million miles in the U.S. and 225 million

worldwide. Copper cable is increasingly being replaced with fibers for LAN backbonesas well, and this usage is expected to increase substantially.

Pure Glass

An optical fiber is constructed of a transparent core made of nearly pure silicon dioxide(SiO2), through which the light travels. The core is surrounded by a cladding layer thatreflects light, guiding the light along the core. A plastic coating covers the cladding to

protect the glass surface. Cables also include fibers of Kevlar and/or steel wires for

strength and an outer sheath of plastic or Teflon for protection.

Enormous Bandwidth

For glass fibers, there are two "optical windows" where the fiber is most transparent and

efficient. The centers of these windows are 1300 nm and 1550 nm, providingapproximately 18,000GHz and 12,000GHz respectively, for a total of 30,000GHz. This


7/25

enormous bandwidth is potentially usable in one fiber. Plastic is also used for shortdistance

fiber runs, and their transparent windows are typically 650 nm and in the 750-900 nm

range.

Singlemode and Multimode

There are two primary types of fiber. For intercity cabling and highest speed, singlemode

fiber with a core diameter of less than 10 microns is used. Multimode fiber is very

common for short distances and has a core diameter from 50 to 100 microns. See laser,WDM, fiber optics glossary and cable categories.

OPERATION OF OPTICAL FIBER

In an optical fiber, a refracted ray is one that is refracted from the core into the cladding.Specifically a ray having direction such that where r is the radial distance from the fiber

axis, (r ) is the azimuthal angle of projection of the ray at r on the transverse plane, (r )is the angle the ray makes with the fiber axis, n (r ) is the refractive index at r, n (a ) is

the refractive index at the core radius, a . Refracted rays correspond to radiation modes in

the terminology of mode descriptors.For the fiber to guide the optical signal, the refractive index of the core must be slightly

higher than that of the cladding. In different types of fibers, the core and core-cladding

boundary function slightly differently in guiding the signal. Especially in single-modefibers, a significant fraction of the energy in the bound mode travels in the cladding.

Diagram of total internal reflection in an optical fiber

The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing

from the cladding (mirror-lined walls), a principle called total internal reflection. Becausethe cladding does not absorb any light from the core, the light wave can travel great

distances. However, some of the light signal degrades within the fiber, mostly due to

impurities in the glass. The extent that the signal degrades depends on the purity of the


8/25

glass and the wavelength of the transmitted light (for example, 850 nm = 60 to 75

percent/km; 1,300 nm = 50 to 60 percent/km; 1,550 nm is greater than 50 percent/km).

Some premium optical fibers show much less signal degradation -- less than 10percent/km at 1,550 nm

FIBER-OPTIC RELAY SYSTEM

To understand how optical fibers are used in communications systems, let's look at anexample from a World War II movie or documentary where two naval ships in a fleet

need to communicate with each other while maintaining radio silence or on stormy seas.

One ship pulls up alongside the other. The captain of one ship sends a message to a sailor

on deck. The sailor translates the message into Morse code (dots and dashes) and uses asignal light (floodlight with a Venetian blind type shutter on it) to send the message to the

other ship. A sailor on the deck of the other ship sees the Morse code message, decodes itinto English and sends the message up to the captain.

Now, imagine doing this when the ships are on either side of the ocean separated by

thousands of miles and you have a fiber-optic communication system in place betweenthe two ships.

Fiber-optic relay systems consist of the following:

Transmitter - Produces and encodes the light signals

Optical fiber - Conducts the light signals over a distance

Optical regenerator - May be necessary to boost the light signal (for long distances)

Optical receiver - Receives and decodes the light signals

Transmitter

The transmitter is like the sailor on the deck of the sending ship. It receives and directsthe optical device to turn the light "on" and "off" in the correct sequence, thereby

generating a light signal.

The transmitter is physically close to the optical fiber and may even have a lens to focusthe light into the fiber. Lasers have more power than LEDs, but vary more with changes

in temperature and are more expensive. The most common wavelengths of light signals

are 850 nm, 1,300 nm, and 1,550 nm (infrared, non-visible portions of the spectrum).


9/25

Optical Regenerator

As mentioned above, some signal loss occurs when the light is transmitted through thefiber, especially over long distances (more than a half mile, or about 1 km) such as with

undersea cables. Therefore, one or more optical regenerators is spliced along the cable to

boost the degraded light signals. An optical regenerator consists of optical fibers with aspecial 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 lasers themselves. The doped molecules then emit a new, stronger light signalwith the same characteristics as the incoming weak light signal. Basically, the regenerator

is a laser amplifier for the incoming signal. See Photonics.com: Fiber Amplifiers for more

details.

Optical Receiver

The optical receiver is like the sailor on the deck of the receiving ship. It takes theincoming digital light signals, decodes them and sends the electrical signal to the other

user's computer, TV or telephone (receiving ship's captain). The receiver uses a photocellor photodiode to detect the light.

USES OF OPTICAL FIBER

The optical fiber can be used as a medium for telecommunication and networking

because it is flexible and can be bundled as cables. Although fibers can be made out ofeither transparent plastic or glass, the fibers used in long-distance telecommunicationsapplications are always glass, because of the lower optical absorption. The light

transmitted through the fiber is confined due to total internal reflection within the

material. This is an important property that eliminates signal crosstalk between fiberswithin the cable and allows the routing of the cable with twists and turns. In

telecommunications applications, the light used is typically infrared light, at wavelengths

near to the minimum absorption wavelength of the fiber in use.


10/25

Parts of a single optical fiber

Core - Thin glass center of the fiber where the light travels

Cladding-Outer optical material surrounding the core that reflects the light back into thecore

Buffer coating - Plastic coating that protects the fiber from damage and moisture

Fibers are generally used in pairs, with one fiber of the pair carrying a signal in eachdirection, however bidirectional communications is possible over one strand by using two

different wavelengths (colors) and appropriate coupling/splitting devices.

Fibers, like waveguides, can have various transmission modes. The fibers used for

longdistance communication are known as single mode fibers, as they have only one strong

propagation mode. This results in superior performance compared to other, multi-modefibers, where light transmitted in the different modes arrives at different times, resulting in

dispersion of the transmitted signal. Typical single mode fiber optic cables can sustain

transmission distances of 80 to 140 km between regenerations of the signal, whereas mostmulti-mode fiber has a maximum transmission distance of 300 to 500 meters. Note

thatsingle mode equipment is generally more expensive than multi-mode equipment. Fibers

used in telecommunications typically have a diameter of 125 m. The transmission core of

single-mode fibers most commonly has a diameter of 9 m, while multi-mode cores are

available with 50 m or 62.5 m diameters.

Because of the remarkably low loss and excellent linearity and dispersion behavior of

single-mode optical fiber, data rates of up to 40 gigabits per second are possible in

realworld use on a single wavelength. Wavelength division multiplexing can then be usedto allow many wavelengths to be used at once on a single fiber, allowing a single fiber to

bear an aggregate bandwidth measured in terabits per second.


11/25

Modern fiber cables can contain up to a thousand fibers in a single cable, so the

performance of optical networks easily accommodate even today's demands for

bandwidth on a point-to-point basis. However, unused point-to-point potential bandwidthdoes not translate to operating profits, and it is estimated that no more than 1% of the

optical fiber buried in recent years is actually 'lit'.

Modern cables come in a wide variety of sheathings and armor, designed for applications

such as direct burial in trenches, installation in conduit, lashing to aerial telephone poles,

submarine installation, or insertion in paved streets. In recent years the cost of smallfiber-count pole mounted cables has greatly decreased due to the high Japanese and

South Korean demand for Fiber to the Home (FTTH) installations.

Recent advances in fiber technology have reduced losses so far that no amplification ofthe optical signal is needed over distances of hundreds of kilometers. This has greatly

reduced the cost of optical networking, particularly over undersea spans where the cost

reliability of amplifiers is one of the key factors determining the performance of the

whole cable system. In the past few years several manufacturers of submarine cable lineterminal equipment have introduced upgrades that promise to quadruple the capacity of

older submarine systems installed in the early to mid 1990s.


12/25

APPLICATIONS OF OPTICAL FIBER

Fibers can be used as light guides in medical and other applications where bright

light needs to be brought to bear on a target without a clear line-of-sight path.

Optical fibers can be used as sensors to measure strain, temperature, pressure and

other parameters.

Bundles of fibers are used along with lenses for long, thin imaging devices called

endoscopes, which are used to view objects through a small hole. Medical

endoscopes are used for minimally invasive exploratory or surgical procedures(endoscopy). Industrial endoscopes (see fiberscope or borescope) are used for

inspecting anything hard to reach, such as jet engine interiors.

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

Optical fibers have many decorative applications, including signs and art,

artificial Christmas trees, and lighting.

ADVANTAGES OF OPTICAL FIBER

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

Large data-carrying capacity (thousands of times greater, reaching speeds of up to3TB/s)

Immunity to electromagnetic interference, including nuclear electromagnetic

pulses (but can be damaged by alpha and beta radiation)

No electromagnetic radiation; difficult to eavesdrop

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

areas with different earth potentials

Low weight

Signals contain very little power


13/25

DISADVANTAGES OF OPTICAL FIBER

Higher cost

Need for more expensive optical transmitters and receivers

More difficult and expensive to splice than wires

At higher optical powers, is susceptible to "fiber fuse" wherein a bit too muchlight meeting with an imperfection can destroy several meters per second . A

"Fiber fuse" protection device at the transmitter can break the circuit to prevent

damage, if the extreme conditions for this are deemed possible.

Cannot carry electrical power to operate terminal devices. However, current

telecommunication trends greatly reduce this concern: availability of cell phones

and wireless PDAs; the routine inclusion of back-up batteries in communication

devices; lack of real interest in hybrid metal-fiber cables; and increased use offiber-based intermediate systems).


14/25

MODULE 2

MICROWAVE COMMUNICATION

INTRODUCTION

The objective of microwave communication systems is to transmit informationfrom oneplace 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, butthetransmitting and receiving antennas must be accurately aligned with each other.

Before the advent of fiber optics, these microwaves formed the heart of the longdistance telephone transmission system.

In its simplest form the microwave link can be one hop, consisting of onepairof antennas spaced as little as one or two kilometers apart, or can be abackbone,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

verylong hop length can be achieved. Hop distances in excess of 200 km arein 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 path

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),

itmay not be possible to place antennas at those two points and achieve asatisfactorycommunication performance


15/25

In order to overcome the problems of line-of-sight and power amplification ofweak signals,microwave systems use repeaters at intervals of about 25 to 30 km inbetween 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

ORIGIN OF MICROWAVE SIGNALS

The first mechanical telecommunications systems were semaphore and the heliograph(using flashes of sunlight), invented in the mid-19th century, but the forerunner of the

present telecommunications age was the electric telegraph. The earliest practicable

telegraph instrument was invented by William Cooke and Charles Wheatstone in Britainin 1837 and used by railway companies. In the USA, Samuel Morse invented a signalling

code, Morse code, which is still used, and a recording telegraph, first used commercially

between England and France in 1851.

Following German physicist Heinrich Hertzs discovery of electromagnetic waves, Italian

inventor Guglielmo Marconi pioneered a wireless telegraph, ancestor of the radio. He

established wireless communication between England and France in 1899 and across theAtlantic in 1901.

The modern telegraph uses teleprinters to send coded messages along


16/25

telecommunications lines. Telegraphs are keyboard-operated machines that transmit a

five-unit Baudot code (see baud). The receiving teleprinter automatically prints the

received message. The modern version of the telegraph is e-mail in which text messagesare sent electronically from computer to computer via network connections such as the

Internet.

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 IFand then

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

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 ofchannels

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

possibilities.


17/25

MICROWAVE COMMUNICATION SATTELITES

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

transmission. The drawback to long-distance voice communication 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. A solution was put forward in 1945 bythe science fiction writer Arthur C Clarke, when he proposed a system of

communications satellites in an orbit 35,900 km/22,300 mi above the Equator, where

they would circle the Earth in exactly 24 hours, and thus appear fixed in the sky. Such asystem is now in operation internationally, by Intelsat. The satellites are called

geostationary satellites (syncoms). 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, and Pacific oceans.

Telegraphy, telephony, and television transmissions are carried simultaneously by

highfrequency radio waves. They are beamed to the satellites from large dish antennae orEarth stations, which connect with international networks.

a general microwave setup


18/25

GENERATION AND FREQUENCY BANDS OF

MICROWAVE SIGNALS

Microwaves can be generated by a variety of means, generally divided into two

categories: solid state devices and vacuum-tube based devices. Solid state microwave

devices are based on semiconductors such as silicon or gallium arsenide, and includefield-effect transistors (FET's), bipolar junction transistors (BJT's), Gunn diodes, and

IMPATT diodes. Specialized versions of standard transistors have been developed for

higher speeds which are commonly used in microwave applications. Microwave variantsof BJT's include the heterojunction bipolar transistor (HBT), and microwave variants of

FET's include the MESFET, the HEMT (also known as HFET), and LDMOS transistor.

Vacuum tube based devices operate on the ballistic motion of electrons in a vacuumunder the influence of controlling electric or magnetic fields, and include the magnetron,

klystron, traveling wave tube (TWT), and gyrotron.

The microwave spectrum is usually defined as electromagnetic energy ranging from

approximately 1 GHz to 1000 GHz in frequency, but older usage includes lowerfrequencies. Most common applications are within the 1 to 40 GHz range. Microwave

Frequency Bands are defined in the table below:

Microwave frequency bands

Designation Frequency rangeL band 1 to 2 GHz

S band 2 to 4 GHz

C band 4 to 8 GHzX band 8 to 12 GHz

Ku band 12 to 18 GHz

K band 18 to 26 GHzKa band 26 to 40 GHz

Q band 30 to 50 GHz

U band 40 to 60 GHz

V band 50 to 75 GHzE band 60 to 90 GHz

W band 75 to 110 GHz

F band 90 to 140 GHzD band 110 to 170 GHz


19/25

MICROWAVE AND WAVEGUIDES

Waveguide, device that controls the propagation of an electromagnetic wave so that thewave is forced to follow a path defined by the physical structure of the guide.

Waveguides, which are useful chiefly at microwave frequencies in such applications as

connecting the output amplifier of a radar set to its antenna, typically take the form ofrectangular hollow metal tubes but have also been built into integrated circuits. A

waveguide of a given dimension will not propagate electromagnetic waves lower than a

certain frequency (the cutoff frequency). Generally speaking, the electric and magneticfields of an electromagnetic wave have a number of possible arrangements when the

wave is traveling through a waveguide. Each of these arrangements is known as a mode

of propagation. Waveguides also have some use at optical frequencies.

In physics, optics, and telecommunication, a waveguide is an inhomogeneous (structured)

material medium that confines and guides a propagating electromagnetic wave.

In the microwave region of the electromagnetic spectrum, a waveguide normally consistsof a hollow metallic conductor, usually rectangular, elliptical, or circular in cross section.

This type of waveguide may, under certain conditions, contain a solid or gaseousdielectric material.

In the optical region, a waveguide used as a long transmission line consists of a soliddielectric filament (optical fiber), usually circular in cross section. In integrated optical

circuits an optical waveguide may consist of a thin dielectric film.

In the radio frequency region, ionized layers of the stratosphere and refractive surfaces ofthe troposphere may also act as an atmospheric waveguide.

In digital computing, the term waveguide can also be used for data buffers used as delaylines that simulate physical waveguide behavior, such as in digital waveguide synthesis.

Propagation in rectangular and circular waveguides


20/25

Waveguide propagation modes depend on the operating wavelength and polarization and

the shape and size of the guide. In hollow metallic waveguides, the fundamental modes

are the transverse electric TE1,0 mode for rectangular and TE1,1 for circular waveguides,seen here in cross-section:

A dielectric waveguide is a waveguide that consists of a dielectric material surrounded byanother dielectric material, such as air, glass, or plastic, with a lower refractive index. An

example of a dielectric waveguide is an optical fiber. Paradoxically, a metallic waveguide

filled with a dielectric material is not a dielectric waveguide.

A closed waveguide is an electromagnetic waveguide (a) that is tubular, usually with a

circular or rectangular cross section, (b) that has electrically conducting walls, (c) that

may be hollow or filled with a dielectric material, (d) that can support a large number ofdiscrete propagating modes, though only a few may be practical, (e) in which each

discrete mode defines the propagation constant for that mode, (f) in which the field at any

point is describable in terms of the supported modes, (g) in which there is no radiation

field, and (h) in which discontinuities and bends cause mode conversion but not radiation.

A slotted waveguide is generally used for radar and other similar applications.

USES OF MICROWAVE SIGNALS

A microwave oven uses a magnetron microwave generator to producemicrowaves at a frequency of approximately 2.45 GHz for the purpose of cooking

food. Microwaves cook food by causing molecules of water and other compounds

to vibrate. The vibration creates heat which warms the food. Since organic matteris made up primarily of water, food is easily cooked by this method.

Microwaves are used in communication satellite transmissions because

microwaves pass easily through the earth's atmosphere with less interference thanlonger wavelengths. There is also much more bandwidth in the microwave

spectrum than in the rest of the radio spectrum.

Radar also uses microwave radiation to detect the range, speed, and other

characteristics of remote objects.

Wireless LAN protocols, such as Bluetooth and the IEEE 802.11g and b

specifications, also use microwaves in the 2.4 GHz ISM band, although 802.11a

uses an ISM band in the 5 GHz range. Licensed long-range (up to about 25 km)

Wireless Internet Access services can be found in many countries (but not the


21/25

USA) in the 3.54.0 GHz range.

Plot of the zenith atmospheric transmission on the summit of Mauna Kea throughout the

entire Gigahertz range of the electromagnetic spectrum at a precipitable water vapor levelof 0.001 mm. (simulated)

Cable TV and Internet access on coax cable as well as broadcast television use

some of the lower microwave frequencies. Some cell phone networks also use the

lower microwave frequencies.

Microwaves can be used to transmit power over long distances, and post-World

War II research was done to examine possibilities. NASA worked in the 1970s

and early 1980s to research the possibilities of using Solar Power Satellite (SPS)systems with large solar arrays that would beam power down to the Earth's

surface via microwaves.

A maser is a device similar to a laser, except that it works at microwave

frequencies.


22/25

MODULE 3

PASSENGER RESERVATION SYSTEM

INTRODUCTION:

The IR carries about 5.5 lakh passengers in Reservation reserved accommodation

every day.

The computerized Passenger Reservation System (PRS) facilitates booking and

Canceling 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 kilometer.

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

Mumbai & Secunderabad.

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.

Wecan 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 works ?


23/25

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

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 boundrate of modem.

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

quadratureamplitude modulate 4 bits & transmitted it in each band. Thus the

speed ofthe modem transmitting at 600 band would be 2400 bps.

The modems can transmit data in two formats: Asynchronous &

Synchronous.

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.

Themultiplexer 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.


24/25

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.

Use of IT in Indian Railway

Passenger Reservation System (PRS)

CONCERT (Country-wide Network of Computerized EnhancedReservation & Ticketing), Indian Railways fully automated PRS software, is acomplexonline distributed transaction application based on client server architecture interconnecting

the regional computing system into a National PRS grid.

The salient features of CONCERT software include allowing passenger from anywhere todo a booking for a journey in any train in any class from anywhere to anywhere, handling

reservation ,modifications cancellation/refunds

e-Ticketing

CRIS (Centre for Railway Information System) has successfully developed the Internet

ticketing solution launched by IRCTC (Indian Railway Catering and Tourism Corporation)

The effort involved interfacing the IRCTC front end with backend PRS Alpha servers,writing procedures for search and queries at the backend, ticket printing on existing clients

and accounting software

UTS (Unreserved Ticket System)

UTS is the complete solution for computerized unreserved ticketing from dedicated counter

terminals and replaces manual Printed Card Tickets/Excess Fare Tickets/Blank Paper

Tickets. In future, ticketing from handheld terminals smart card, automatic vendingmachines, etc. is also envisaged

IVRS (Interactive Voice Response System)

IVRS is a telephonic enquiry system which information such as Passenger NameRecord

(PNR) enquiry, Train Arrival/Departure information enquiry through NTES, andBerthavailability position in any train, in multiple languages

NTES (National Train Enquiry System)


25/25

NTES provides arrival/departure as well as current status information

about any passenger train in the entire Indian Railways

NTES is parallel to PRS.

The servers are located at five metros i.e. Delhi, Kolkata, Mumbai, Chennai,

Secunderabad and all are interconnected. Entries are made regarding running of train every

half an hour at various locations including divisional headquarter all over the IndianRailways. NTES is used by IVRS and other web enabled services and mobile services for

providing train information to the public

indian railway 4

Documents