Mini Project

CHAPTER 1: INTRODUCTION

1.1 About Indian Railways:

Indian Railways is the state-owned railway company of India, which owns and

operates most of the country's rail tra.nsport. It is overseen by the Ministry of Railways of

the Government of India.

Indian Railways has more than 64,015 kilometers (39,777 mi) of track and 6,909

stations. It has the world's fourth largest railway network after that of the United States,

Russia and China. The railways traverse the length and breadth of the country and carry

over 20 million passengers and 2 million tons of freight daily. It is one of the world's

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

rolling stock, IR owns over 200,000 (freight) wagons, 50,000 coaches and 8,000

locomotives.

Railways were first introduced to India in 1853. By 1947, the year of India's

independence, there were forty-two rail systems. In 1951 the systems were nationalized

as one unit, becoming one of the largest networks in the world. IR operates both long

distance and suburban rail systems on a multi-gauge network of broad, meter and narrow

gauges. It also owns locomotive and coach production facilities.

Initially, the Indian railways were both designed and built by the British, during

their colonial rule of the subcontinent.

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

India, via the Ministry of Railways. As of December 2010, the Railway Ministry is

headed by Mamata Banerjee, the Union Minister for Railways, and assisted by two

ministers of State for Railways. Indian Railways is administered by the Railway Board,

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

1.2 Railway Zones:

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,

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and finally 17 in 2010. 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.

Each of the seventeen zones, Including 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.

1.3 Broad Construction of any Telecommunication Cable:

Core:

All the insulated conductors compactly arranged in pairs, units and super units constitute core of the cable

Moisture Barrier:

As the presence of moisture deteriorate the quality of insulation of the telecom cables, moisture barrier protects entry moisture into the core of the cable.

Protection::

Telecom cables require Protection

o from probable mechanical damages

o from water and chemicals or soil conditions

o from Induction due to Electrical lines

o from diggings by different agencies and individuals

o from damages while handling

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1.4 The classification of underground cables with regard to design features:

Place where it is used - Underground / overhead / submarine

Insulation material used - Paper / polythene cables

The filling compound - Dry core / jelly filled cables

Mechanical protection - Armoured / unarmoured cables

Place of utilization - Primary / Distribution / Junction cable.

System for which used - Co-axial / PCM

Type of conductor - Copper cable / Optical fibre cable

Gauge of the conductor - 0.40 mm / 0.50 mm 0.63 mm / 0.90mm

Pressurization of core - Pressurized / unpressurised cables

1.5 Design Features:

Before discussing the above classifications in a nutshell let us know what are the purposes of the above Design features in a underground cables.

Figure 1.1: Mechanical Protection

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1st pair B Limb

3rd pair A Limb

2nd pair B Limb

1st pair A limb

Insulating material PVC / PAPER

Annealed CopperConductors

SheathLSDC / PVC

C

O

R

E

Filling material Dry air / Jelly

MECHANICAL PROTECTION2 LAYERS OF GI STRIPS

1.6 Purpose of Insulation Underground Cables:

The insulation is used to separate the conductors bunched in a unit to prevent short circuit between two conductors in a pair or between conductor of one pair with the conductor any other pair in the unit or core in the cable.

The insulation is used as SHEATH to separate the insulated conductors from being corroded or eroded in soil.

The insulation is being used for marking / identifying the pair or conductor in the unit and in the cable as a whole for that matter.

The insulating material is used for preventing the grounding or earthing of the conductors.

The insulating material is used for preventing the corrosion of armouring

Transmission characteristics of the cable

In the primitive stage paper insulation chosen as it has good di-electric properties and low specific inductive capacity which is about 1.5. Its physical properties also enable large proportion of air as dielectric. The ideal dielectric for telecom cable is air which has specific inductive capacity of 1.0. The thickness, width and number of wraps per meter of insulating paper is selected to achieve the required mutual capacitance of cables.

The Polythene insulation is easy to apply and have desired electrical characteristic such as low dielectric constant, lo dissipation factor (loss) and high dielectric strength. Mechanically it is tougher than paper and has abrasion resistant with ample tensile strength and elongation.

The insulating resistance measurement shall be measured with a DC voltage of magnitude not less than 500V after steady electrification for one minute. The insulation resistance values between each conductor in the cable and all the other conductors connected together and to the screen and earth shall not be less than 5000 Mega ohms / km at Room temperature. (Cable length in Km x observed insulation in Mega ohms).

1.7 Pairing and Overlay:Two insulated conductors shall be twisted together with uniform lay to form a pair. The length of the lay of any pair shall be different from that of adjacent pairs. The lay of various pairs shall be so chosen as to satisfy the capacitance unbalance requirements and cross-task requirement.

1.8 Unit Formation:

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The pairs are then assembled into units with different length of unit twists assigned to different units. These units are then assembled into a completed cable core.

1.9 Core:Core wrappings are applied to the completed cable core to hold the units together and provide high di-electric strength from core to shield and to protect the conductor insulation from damage due to the heat of sheathing operation. In PIJF cables non-hygroscopic and non-wicking polyester tape is used as core wrapping.

1.10 Filling compound:The cable should be filled with suitable water resistant compound which shall be compatible with the insulation, binders and tapes used in the cable. It shall be homogenous and uniformly mixed material containing an anti-oxidant. It shall not contain dirt, metallic particles or other foreign matter.Paper insulated cables: Dry air onlyPolythene insulated cables: Jelly compound.

1.11 Screen:

An aluminum tape coated with polythene / copolymer on both sides shall be applied over the cable core with a minimum overlap of 6 mm for all sizes of cables. The nominal thickness of the aluminum tape shall be 0.2 mm and that of polythene / copolymer coating on each side 0.05 mm.

The aluminum tape shall be sealed at the overlap and bonded to the inner surface of polythene sheath extruded over it. The tape shall be electrically continuous throughout the length of cable.

1.12 Sheath:

A moisture resistant, gas tight sheath must be applied to all the paper insulated cable other wise relative humidity conditions throughout will increase and insulation resistance will decrease. The sheath also protects the cable form damage during installation and service.

The sheath shall be reasonably circular and free from pinholes and other defects. The variation between maximum and the minimum diameter at any cross section shall not exceed 5mm.

Paper insulated cables: Lead sheath or Polythene sheath

Polythene insulated cables: Polythene sheath only.

1.13 Conductor:

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Each conductor is a solid round wire made of annealed high conductivity copper of diameter 0.32 mm, 0.40 mm, 0.50mm, 0.63mm and 0.90 mm.

1.14 Armouring:In the armored cables bedding and amour are provided over the sheath to be followed by jacket. Then the cables are called armored cables. If this arrangement is not done then we call them as un armored cables.

1.14.1 Bedding: Two close helical lapping of polythene or polypropylene tape is applied over the sheath to provide sufficient mechanical protection during armouring. Each take is applied with a minimum 5% overlap. The second tape will cover the overlap of the first tape evenly.

1.14.2 Nominal thickness of the Galvanised steel Tape armouring:

Diameter of cable over Polythene sheath Thickness of Steel tape

Upto 40 mm 0.5 mmAbove 40 mm 0.8 mm

Armouring is the application of two layers of galvanized steel tape both applied helically in the same direction with a gap in the first tape of 25% +/- 10 % of the nominal width of the tape, the second tape evenly covering the gap of the first tape. The overlap of the second over the first shall not be les than 15% of the nominal width of the tape on either side.

1.14.3 The standard armouring types are:

Aerial tape armour

Jute protection

Burried tape armour

Modified tape armour

Steel armouring and polyjacketing

Corrugated steel armouring and jacketing.

1.15 Jacket :

Most cables serve their lives with a basic sheath but after armouring the armouring is to be protected from getting rusty and corrosion and jacket is the protection which does the job. It should be reasonably circular, free from pinholes and other defects.

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1.16 Nominal thickness of the Jacket:

Diameter of cable over Polythene Jacket Thickness of Polythene Jacket

Upto 46 mm 1.4 mmAbove 46 mm up to 64 mm 1.8 mmAbove 64 mm 2.2 mm

1.17 Identification and Length markings on a Cable:

To enable proper identification of Telecom cables the following markings shall be embossed, engraved or printed on the polythene jacket in case of armoured cable and on the sheath for unarmoured cables. These markings are at an interval of one meter throughout the length and are distinct and visible to the naked eye from a distance of about 1 meter.

Telephone handset emblem

Name of the Manufacturer

Year of Manufacture

Capacity of the cable in pairs

Size of the conductor

Length marking

1.18 Sealing of the Ends:

The cables will be sealed with thermo shrinkable end caps of adequate thickness after completion of all tests in factory before dispatching to various stores and workplaces directly.

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CHAPTER 2: POLYTHENE INSULATED JELLY FILLED CABLES

2.1 Introduction:These are popularly known as PIJF cables and consist of twisted pairs of polyethylene insulated copper conductors.

Paper insulated cables (LSDC, PCUT, PCQT, PCQL & PCQL ) are the primitive underground cables that are used in the Telecommunications network. These cables are available up to 1800 pairs. Later on due to various factors like escalation in the cost of Lead and more incidence of faults due to paper insulation the Polythene insulated Jelly filled cables ( Popularly known as PIJF ) are used extensively now a days in the telecommunication networks. The PIJF cables are available up to 3600 pairs.

Some constructional features of Paper insulated cables are dealt in Job Aid – I, for academic interest and as still a few number of these cables are still serving some of the telecommunication networks.

The Pressurization of dry core paper insulated cables is now a avoidable feature as the replacement of paper-insulated cables with PIJF cables is nearing completion. As the PIJF cables are filled with Jelly as filling compound which takes care of prevention of entry of moisture / water into the core of the cable.

2.2 Polythene insulated Jelly Filled Polythene Sheathed Under Ground Cable:

(a) Number of Pairs:The cables shall be in sizes 5, 10, 20, 50, 100, 200, 400, 800, 2000, 2400, 2800, 3200 and 3600 pairs.

(d) Conductors:Each conductor shall be insulated with polyethylene of insulating grade. Different gauges of conductors 0.32mm, 0.40mm, 0.50mm, 0.63mm, and 0.90 mm are used in the cables.

Each conductor shall consist of a solid wire of annealed high conductivity copper smoothly drawn & circular in section, uniform in quality, resistance and free from all defects.

The average resistance of all the conductors in the cable shall not exceed the values shown in Table given below.

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Nominal diameter of conductor

Resistance per km per conductor at 20 0 C

Tolerance on conductor Resistance

Minimum elongation of conductor

Min % conductor Resistance unbalance

Attenuation at 20 deg C

in mm ohms/km Ohms /km percentage Average Db/km0.32 223 - 15 1.5 -0.40 135 +/- 4 15 1.5 12.00.50 86 +/- 3 15 1.0 8.250.63 58 +/- 2 18 1.0 6.300.90 28 +/- 1 18 1.0 4.40

The Percentage of Resistance Unbalance of any individual pair tested shall be calculated as follows::

Percentage of Resistance Unbalance =

Where R1& R2 are the resistances of individual conductors of pair under test and R1 > R2

2.2.1 The temperature correction for attenuation is:

Attenuation at 20 0 C =

2.2.2 Correction Factor for Conductor Resistance:

Temperature in deg C at which conductor Resistance is measured 10 20 30 40 50

Multiplier constant for conversion to 20 deg C 1.0419 1.0000 0.9622 0.9271 0.8945

(c) Insulation:Each conductor shall be insulated with solid medium density polythene of density 0.926 to 0.94 to a thickness. The insulation should be uniform, smooth and free from all defects. The insulation will have following color for identifying pairs /conductors under normal lighting conditions.

2.2.3 Code for Wire Identification:

Primary colors Secondary colors

For 1st wire in a pair For 2nd wire in a pair and binder tape of unit in 50pr/100pr unit

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( R1 - R2 ) x 100 R1 + R2

Attenuation at t degrees C

1 + 0.0018 (t-20)

White BlueRed OrangeBlack GreenYellow Brown

Slate / Gray

(d) Unit:A number of twisted pairs laid up to form a group shall constitute the unit. The color scheme of pairs and wires in a unit shall be read as below.

2.2.4 Code for Tape or Binder for Unit Identification:

Unit number 1 2 3 4 5Color of Binder Blue Orange Green Brown Slate / Gray

2.2.5 Code for Conductor Insulation:

Pair No ColorFirst Wire Second Wire

1 White Blue

2 White Orange3 White Green4 White Brown5 White Slate / gray

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A

6 Red Blue7 Red Orange

8 Red Green9 Red Brown10 Red Slate / gray11 Black Blue12 Black Orange13 Black Green14 Black Brown15 Black Slate / gray

16 Yellow Blue17 Yellow Orange18 yellow Green19 Yellow Brown20 Yellow Slate / gray21 Natural Blue22 Natural Orange

Note:(a) In 5 pair cable, color code specified for pairs 1 to 5 above is used.(b) In 10 pairs cables and 10 pairs units of 50 pair cables, color code specified for pairs 1 to 10 is used.(c) In 20 pair cables and 20 pairs units of 100 pair cables, color code specified for pairs 1 to 20 shall be used.

(d) The number of the pairs with respect to the color scheme is only for the purpose of identification of pairs, the actual numerical sequence of the pairs varies as the size increase.

The different colors of the binder shall be readily distinguishable under normal lighting conditions.

(e) Stranding:A 50 pair cable consists of 5 number of 10 pair unitsA 100 pairs cable consists of 10 number of 20 pair units.

These units shall be stranded into a compact and symmetrical cable. the sequence of the units in the cable shall be same throughout the length of the cable.

An open lapping of 0.02 mm miler tape of any other suitable material of appropriate thickness shall be applied for each unit.

The tapes shall be so colored and have lay not exceeding 200 mm. This tape is not necessary on the 5 pairs, 10 pairs and 20 pairs cables.

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C

B

In case of 5, 10, 20 and 50 pair cables, one spare pair will be stranded as the last pair. The color of the spare pair shall be in accordance with pair No. 21 of above table .

In the case of 100 pair cable, 2 spare pairs shall be provided. the color of the pair shall be as specified for pair No. 21 & 22 of above table. The spare pairs in the case of 50 pairs and 100 pairs cables shall be provided within the cable core, but shall not be within any unit.

The 200pair and 400 pair cables ( cables above 100 pr and unto 400 pairs) will be formed by super units of 50 pairs. and the units stranded in the form of layers

The cable over 400 pairs is formed be the super units of 100 pairs and the units stranded in the form of layers.

CHAPTER 3: COMMUNICATION EQUIPMENT

3.1 Four Wire Station Control Telephone

3.1.1 APPLICATION:

The 4 Wire Station Control Telephone to use with 4 Wire Way Station, which is installed on the way side stations.

3.1.2 DESCRIPTION:

The 4 wire station control telephone consists of dynamic type Transmitter and Receiver Insets (RT 200). It has an Led to indicate that the station is called, a buzzer for hooting while the station is called. It has a pre-amplifier circuit in the Trans side to give an output

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voltage of 250mv across the line with 1120 ohms load impedance, for an input of 5mv across the dynamic type transmitter (220 ohms load impedance). The 4 wire control telephone consists of ABS body, Hand Micro Telephone, with press to talk Micro Switch, Cradle Switch, Coil cord & straight Cord, 6 way Rosette Box, Buzzer & LED.

3.1.3 CONSTRUCTION:

The body, handset and other plastic parts are of ABS plastic. It consists of 1.5 meter long coiled cord and a straight cord terminated in a rosette box.

3.1.4 SPECIFICATIONS:

Power supply : 12V + 20% - 10%Dielectric strength : 1KVAC 50Hz 1 minuteInsulation Resistance@500VDC : 10MΩ between all wires in the terminal strip

and body. DC Resistance of the cord : 1.15 ohms/meter at 20.Send level across, mic & ground : 250mv adjustable across 1120 ohms load mic & 3 & 4 terminals. 5mv at 1kHz ground.(Handset terminals)Receive Efficiency : clear tone heard in the receiver Tone of

1KCat -10dB fed to 5 & 2 terminals across 1120 load.

Micro switch Mechanism : When PTT pressed continuity between 2 & 7terminals.

Cradle switch Mechanism : Continuity between 1 & 2 terminals when handset off the hook.

Working of buzzer : 12VDC at 2 & 4 terminals. Short 4 & 6 and Buzzer should Buzz.

3.2 Two Wire Way station Control Telephone:

3.2.1 APPLICATION:

The 2 Wire Station Control Telephone used for 2W way station equipment which is installed on the way side stations.

3.2.2 DESCRIPTION:

The 2 wire station control telephone consists of dynamic type Transmitter and Receiver Insets. It has an Led to indicate that the station is called, a buzzer for hooting while the

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station is called. It has a pre-amplifier circuit to give output voltage of 775mv across the line with 600E load impedance at the input of 5mv across dynamic type transmitter. The 2W control telephone consists of ABS body, Hand Micro Telephone, with press to talk Micro Switch, Cradle Switch, Coil cord & straight Cord, 6 way Rosette Box, Buzzer & LED.

3.2.3 CONSTRUCTION:

The body, handset and other plastic parts are of ABS plastic. It consists of 1.5 meter long coiled cord and a straight cord terminated in a Rosette box.

3.2.4 SPECIFICATIONS:

Power supply : 12V, 6V and 3V DC + 20% - 10%Dielectric strength : Between all wires in the terminal strip and metal @1KV, 50Hz AC parts(Chassis).Insulation Resistance@500VDC : >10MΩ between all wires in the terminal strip and

metal parts (Chassis). DC Resistance of the cord : ≤1.15 ohms/meter at 20C.Send level across L1 & L2 : ≥775mV.Side tone : <100mV.Receive efficiency at 193mv : ≥100mV.Insertion loss : ≤0.2dB Listen condition.

≤0.8dB Talk condition.DIMENTIONS : 220×180×75mm.WEIGHT : <1Kg.

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Figure 3.1: 2 Wire Control Telephone

3.3 Universal Way Side DTMF control telephone:

Universal Way Side DTMF control telephone is used for control communication on 4 wire/2 wire control telephone as well as way station equipment for both 4 wire & 2 wire control communication systems. The telephone is assembled in Siemens type ABS plastic body. The telephone is capable of work on both 4 wire & 2 wire omnibus circuits by using a changeover switch provided inside the telephone and the telephone works on

Over head 2 wire system. Underground cable 4 wire system. OFC or Digital Microwave system.

The telephone instrument consists of the following parts:a. Telephone housing, HMT, Dynamic Insets, Rosettee Boxb. Speech circuitsc. Decoder circuitd. RBT circuit etc

Electro Dynamic Transducers (RT200) are used perform functions of transmitters and receivers. One charge over switch is provided at PCB of the telephone. It will work one side with 4 wire control line and opposite side with 2 wire control line. The telephone will work on 12V DC with 20% supply voltage.

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Specification : RDSO/SPN/TC/36/00Power supply : 12V DC with 20%Current consumption (max) : 30mA in idle condition

75mA during conversation125mA during ringing period

Decoder : The decoder circuit is designated to work the Signaling system of DTMF control office Equipment.

Ringer : On receipt of the valid code piezo electric buzzer will be activated even if the handset (HMT) is OFF cradle.

Ring back tone : After the buzzer the telephone is activated, a ring back tone is automatically transmitted to the control office in acknowledgement of the receipt of the ring. The level of the ring back tone across Trans terminal of the telephone is adjustable between -6dBm to -10dBm.

4 WIRE SEND EFFICIENCY:

The receiver replaced by a non-inductive : The level across1120Ω is greater than resistance of 200Ω. 0dBm.The oscillator level to be adjusted such that it is -44dBm at1000Hz. The Trans terminals of rosette box terminated by resistance of 1120Ω. Total harmonic distortion : Not more than 3% Frequency response : +/- 3dB in the frequency range 300 to

3400Hz.

2 WIRE SEND EFFICIENCY:

The receiver replaced by a non-inductive : The level across L1, L2 (600Ω) is resistance of 200Ω. greater than 0dBm.The oscillator level to be adjusted such that it is -44dBm at1000Hz. L1 & L2terminals of rosette box terminated by

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resistance of 600Ω. Total harmonic distortion : Not more than 3% Frequency response : +/- 3dB in the frequency range 300 to

SIDE TONES (2 WIRE):

Oscillator level -44dBm at 1000Hz : The level across R1 & R2 not more across Trans terminals L1 & L2 than -18dBm.terminals of rosette box terminatedby resistance of 600Ω.

4 WIRE EFFICIENCY:

The line simulated by non inductive : the level across R1 &R2 greater than resistance of 560+560Ω the level and -26dB.frequency -20dBm at 1000Hz.Total harmonic distortion : Not more than 3% Frequency response : +/- 3dB in the frequency range 300 to

3400Hz.

2 WIRE EFFICIENCY:

The line shall be simulated by non inductive : The level measured across R1 resistance of 300+300Ω. Oscillator level to be & R2 not be less than -18dB.adjusted across L1 & L2 -12dBm at 1000Hz.Total harmonic distortion : Not more than 3% Frequency response : +/- 3dB in the frequency range 300 to

3400Hz.

INSERTION LOSS:

4 wire ON hook condition : Not be greater than 0.5dBm4 wire OFF hook condition : Not be greater than 1.0dBm2 wire ON hook condition : Not be greater than 0.5dBm

2 wire OFF hook condition : Not be greater than 0.8dBm

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Figure 3.2: Universal Way Side DTMF Control Telephone

3.4 Six Pin Emergeny Plug and Socket:

Six pin plug and socket used for communication on 4 wire basis on emergency control circuits from the points provided for this purpose along the side of the track in AC electrified areas. These are made of glass filled ABS plastic (unbreakable).

The transmitter, receiver of the 4 wire emergency portable telephone shall be connected to the six pin plug by means of 6 way cord provided in the 4 wire emergency portable telephone.

Socket shall be fixed in the socket box. The socket be connected to trans, receive of the emergency control circuit, derived from the main cable through transformer joint.

Six pin plug & socket consists of the following components:a. Six pin plug shall consists of plug top cover, plug base and plug pin.b. Six pin socket shall consists of socket base, socket fixing clamps, contact spring,

rivet and buffer pin.

Six numbers of plug pins are embedded in the plug base. The wires are connected on the screw terminals of the plug base as per the pin configuration.

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SPECIFICATION:High voltage test : plugs and sockets outlets shall satisfactorily

withstand a voltage of 2KV r.m.s for 1min without breakdown when applied between

i. All terminals looped and body.ii. Between terminals.

Insulation Resistance : Insulation Resistance when measured at a voltage of 500V DC between all terminals looped to together and the body, and in between terminals shall not be less than 100MΩ.

Contact Resistance : The contact resistance of each pin shall not exceed 20 milli Ohms.

Contact pressure : The contact pressure when measure with a pressure gauge applied on the contact spring front of the socket shall not be less than 500gms.

Dimensions : The outline dimensions are given in the drawing.

Figure 3.3: 6 Pin Emergency Plug and Socket

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3.5 4W/2W Portable Emergency Control Telephone for Use in Electric Field Sections:

3.5.1 SCOPE:

The Portable Emergency Control Telephone is a part of the 4Wire/2 Wire emergency train traffic control system. This telephone provides inter communication between any way side point along the train route and controller. This can be connected through 6 Pin Socket located along the railway track in 4W side and 2 Wire lines in 2 wire side. The telephone has ‘Trans’ and ‘Receive’ speech circuits. The telephone works on 3 VDC with the aid of 2 Nos. of 1.5V dry cells. The entire circuit, HMT and the battery container are housed inside the M.S body provided with shoulder strap to carry easily. With the aid of switch, this telephone can be selected for 2W or 4W operation.

3.5.2 FEATURES:

Glass epoxy boards are used for better environmental performance. Ferrite Core Transformer is used for miniaturization and better quality

performance. High reliability press to talk and press to call switches are used. Sealing arrangement is provided for preventing pilferage of battery. Rugged construction of box to ensure rough handling. HMT is of Siemens type or type 677 of ITI, made with ABS moulding which is

unbreakable.

3.5.3 TECHNICAL DESCRIPTION:

The indication transformers are made of high permeability. Ferrite cores meet acceptable specification of grade 3, category 3 to IS:6297, Part1/Part3.

The windings are terminated on glass epoxy PCB. The transformers are duly marked Trans and Rec. The windings used comply with IS:4800, Part1. The transformers are duly impregnated/Potted. The handset is of Siemens type or type 677 of ITI make with ABS plastic which is

unbreakable and has 1 meter long five core coil cord terminated to the PCB using two pin connectors.

The press to call and press to talk switches are of LCSO approved make. Terminals are provided to connect Battery and Handset internally.

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The outgoing four cable is connected to 6 pin plug using 2 meter long standard cord and 2 lines are connected to the terminals marked L1&L2.

The internal wiring is done using 0.5mm over all dia 7 strand PVC insulated wire as per IS:5608.

The supply is 3V DC with the aid of 2 Nos. of 1.5V dry batteries, type R20 of IS:8144. The batteries are housed in a battery box which is fitted on a MS plate.

High voltage test and 2KVRMS, 50Hz for 1 min. 4W SIDE 2W SIDEi. Between Primary/Secondary : No breakdown

N.Aii. Between Primary/Earth : No breakdown N.A

iii. Between Primary/ Earth : No breakdown N.A

Insulation Resistance at 500 VDC/Ambient Temp. 4W SIDE 2W SIDEi. Between Primary/Secondary : >100M

>10MΩii. Between Primary/Earth : >100M >10MΩ

iii. Between Primary/ Earth : >100M >10MΩ

3.5.4 CONSTRUCTION:

The box is made of M.S Sheet with spot welded brackets and has a middle plate. Under this middle plate, battery container is fixed and the battery can be replaced easily from the top. The PCB made of epoxy glass is fitted with the trans and receive circuitry. The cables are taken from the bottom through grommets for 4 Wire. Two terminals marked L1 & L2 are provided on the top of the plate, using which the telephone can be selected for 2 Wire/$ Wire operation. The complete box can be closed after taking out the coil cord, straight cord and connection from L1,L2 terminals through special outlet shrouds provided.

Dimensions : 260×135×160mmWeight : 2.5KGS(Approx.)

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Figure 3.4a: 2/4 Wire Portable Emergency Control Telephone

Figure 3.4b: 2/4 Wire Portable Emergency Control Telephone (Inside View)

3.6 Block Bell Equipment:

3.6.1 APPLICATION:

The Block Bell Equipment is a part of the block instrument which is provided at the end of the block sections of cabins /ASMS. DC impulses cannot be sent in AC electrified area since block circuit is converted from overhead alignment to under ground cable terminated transformer at both of the ends. This equipment is used in AC electrified area to convert the DC impulses to AC at the sending end and AC impulses to DC all the receiving end.

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3.6.2 TECHNICAL DESCRIPTION:

The Equipment is a single transistor oscillator to give 45V AC across 1120ohms. This also has a full wave rectifier circuit to rectify the received AC voltage and to energize a relay.

The plunger is connected to terminals TS9 and TS10 of terminal strip (Refer circuit diagram enclosed). Hen the plunger is pressed 12 V.DC supply is fed simultaneously to the Transistor Oscillator and the Relay So/2. The output of the oscillator, Viz, 45volts at 150Hz, is thus made available at terminals. TS3 and TS11 through the energized contacts of Relay So/2. This is fed to the line. At the distant station, this voltage from the line is fed to terminals TS3 and TS11 at the Block Bell Equipment installed at the station. Though the normally closed contacts of Relay So/2, this voltage is fed to the bridge rectifier. This rectified voltage is available, as desired from terminal TS4 and any of the other terminals, namely, TS5, TS6, TS7, TS12, TS13, TS14 and TS15 for ringing the bell.

3.6.3 CIRCUIT DESCRIPTION:

When the plunger is operated, the single transistor is energized of the oscillator gives an output 60V (open circuit) @ 150Hz and 45V (across 1120 Ohms.) at 50Hz., sinusoidal at TS3 and TS11.

3.6.4 SPECIFICATION:

a) Input Voltage : 12V.DC ± 20%, -10%b) Output Voltage : < 1 Ampc) Output Voltage across 1120 Ohms : 45V.AC± 5%d) Output Frequency : 150HZ ± 5HZe) Wave- Shape : Sinusoidalf) Dielectric Strength

(Between all current carrying points and above) : No Breakdowng) Insulation resistance at 500VDC : More than 10M Ohms

3.6.5 CONSTRUCTION:

The box is made of aluminum alloy and it has a hinged front door, with a knurled screw and sealing arrangement. The cables can be wired through the grommet hole provided in the rear, to the terminal plate.

The terminal plate is marked for wiring purpose. A wiring diagram is also pasted on the rear of the door.

WEIGHT: 2.7KGS (App)

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Figure 3.5: Block Bell Equipment

CHAPTER 4: FLEXIMUX

4.1 General Description:

The Flexilv LJX is a programmable add/drop multiplex equipment which combines variety of voice and data traffic of public or private network into a 2.048 Mbps stream in CCITT-ITLJ-T G.73 1/G.732 format. For voice transmission the equipment accommodates different types of interfaces ranging from 2W/4W E&M interface to subscriber, exchange and junction line interfaces. The digital interface units consists of both high speed and low speed accesses to accommodate variety of data communication applications. Multiple low speed data are combined into one 64 Kb/s channel for efficient utilisation of information bandwidth. The add/drop feature of the F1ex1MUX is realised through the use of a high performance time/space non-blocking cross-connect switch with four independently controlled serial time division multiplexed buses. Conferencing of voice is done through a separate Digital Signal Processing circuit in digital format conforming to CCITT-ITU-T G.7 11 A- law format. All the signalling information are handled by a microcontroller which can also optionally take care of some signalling protocol conversion if required. The system can be programmed for its channel assignments locally through a portable laptop computer or remotely from a Central Supervisory Terminal through a polled data channel derived through unused National bits or the overhead bit-stream of the transmission equipment. The same channel is also used for Network Monitoring and Control operations. Polled mode of operation allows it to be used in tandem, loop or star to suit the network structure of the user. Various diagnostics features are built-in the system which eases the maintenancc of the network. -

4.2 System Architecture

The F1exiMUX is .a compact unit based on the 19 inch mechanical construction measuring 10.5” H (6U) x 19” W x 19” D (267mm x 483mm x 457mm). This 6U sub rack is a common mechanical housing with a bussed backplane which accepts all the modules with vertical mounting making a modular equipment concept possible. LEDs on the front panel indicate the status of all the individual modules. The 2 Mbps streams are accessed from the rear side either through coaxial connectors for 752 interface or through wire wrap posts for 1202 balanced connection. All the voice, signalling and data information are accessed from wire wrap connectors mounted at the back. The NMS can be accessed through a 9 pin D-shell connector, mounted in the backplane or from RJ1 1 jack mounted in the facia of Network Interface Module. The basic system consists of the Network Interface Module, Tributary Module, Power Supply and the sub rack with the backplane. Analog and digital services are realised with interface specific access units connected to an internal 2 Mbps bus. The realisation concept of the FlexiMUX is presented in Figure 1. Each, of the access units accommodates one to four channels depending on the complexity of the interface. Each individual service channel consumes one time slot (e.g. voice and high speed data up to 64 Kbps) and fractional time slots (e.g.

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low speed data unto 19.2 Kbps) of the 30 time slots available for use with the 2 Mbps stream. For voice channels various interface options are available to suit the customers requirement. The interface units are small adaptor cards which can be plugged into any one of the four adaptor sockets available on a voice access module. Flexibility of these plug-in modules allows free inter-mixing of interface units on a particular voice access module. The various interface options available at present are

a. 4W/2W E&M b. Subscriber Interface c. Exchange Interface d. Hot Line Interface

Figure 4.1: System Architecture

The sub rack has altogether 13 slots for housing the various modules. Out of these slot 1 & 2 are dedicated for PSU Modules (in case of redundant power supply) and slot 2 & 3 are dedicated for the Network Interface • Module (MM) & Tributary Module (TM). Slot 3 to slot 13 is meant for housing various access modules for both voice and data interface. Each of these slots supports access to 4 Time Slots of the 2 Mbit/s stream. Thus slot 5 to slot 11 supports altogether 28 Time Slots of the 2 Mb/s bus. Slot 12 and slot 13 has equal and parallel access to time slots 30 and 31. This has been done for efficient

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utilisation of the bit stream during sub multiplexing of a time slot for low speed data. The structure of the sub rack and its arrangement of time slot allocation is shown in Fig4.2.

Figure 4.2: Sub rack

Access to the 2 Mb ports is available from the backplane from the rear side. Separate connectors are available for 75 2 and 120 2 impedance matching. For 75 Q, spinner type threaded connector has been provided for firm contact. For 120 2 , three pin 1mm square post has been provided for either wire wrap termination or termination through self lock header socket. A separate port is also available for driving the system using external clock. Extension of voice and data has been provided on Euro type wire wrap connectors. This has enough space for wrapping 0.5mm or 0.6mm telephone cable normally used for telecommunication. Separate connector has been provided feeding input -48V DC power supply to F1exiMUX. The backplane. also provided a D-Shell 9pm connector for interfacing the V24 / RS232C serial link of the Network Monitoring System. NMS can also be accessed from RJ1 1 jack located at the front of NIM.

4.3 Power Supply Module:

The power supply unit operates from 48V supply. The input power is fed through a surge protector and filter section to protect the system from high voltage spikes and lightning strikes coming along the. power line. The first stage is a Gas Arrestor which can absorb high energy pulses. This is followed by LC filter which then faces a transient protector to bring down the spikes within acceptable limit. The primary supply is connected to earth through high voltage capacitors to bypass AC noises but ensuring DC isolation. Each PSU has three separate switching power supply modules, one for +5V, one for ±1 OV and another for +80V. They are also mutually isolated with each other. +5V is used to operate all the digital devices of the system. The ±1OV is post regulated in different card to ±5V and is used to drive the analog devices. The card also has under-voltage and over-voltage alarm for both input and output. The capacity of the PSUs are overrated adequately so that each of the PSUs individually can support the whole system.

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LED Display Status: PSU OK It is a green LED. When the power supply is frmnctioning properly it glows. PSU ERR It is a yellow LED. When there is output undervoltage alarm it glows. SHUT DN It is a red LED. When the power supply goes into shutdown it glows. SW1 It is the power ON switch. SW2 It is the switch for resetting the power supply card.

4.4 Circuit Description:

The input -48V supply is fed through a surge protection section Li & SA. Diode CR1 protects the system from reversal of input voltage. C48, Cl & C6 are input filter capacitors. Qi along with CR2 & CR4 provides crowbar protection for the input going beyond 58V. Q2 is a series regulator which gives the initial power to the switching regulators Ui, U3 & U5 for its operation Switching regulator Ui and its associated hardware generates +5V power, U3 generates ±1OV and U5 generates +80V supply. Primary and secondary of the power supplies are fully isolated through the transformer Ti, T2 & T3 and feedback opt isolators U2, U4 & U6. The +5V, ±1OV and +80V at the secondary side is also mutually isolated. Use of entirely separate hardware for +5V, ±1OV and +80V helps to maintain much better regulation of the derived power supplies compared to that with a single switching regulator. R8, R9 and C8 fixes the oscillation frequency of the switching regulator of Ui to 80KHz approx. Reference voltage from Ui :16 is fed to non- inverting input of the error amplifier Ui :2 through a filter R44, R7 & C7. Opt isolator U2 provides a feedback signals of the +5V output through the resistance combination R6 & R4. R5 & C9 provides frequency compensation for the error amplifier. The output switching pulses from Ui is fed to the switching transistor Q3 which in turn drives the switching transformer Ti. Snubber circuit consists of R16, C13, CR7 & R15, C12 & CR14. R13 & R14 gives feedback of the overload condition to Ui. Operation of ±1OV and +80V power supply is same as that of the +5V power supply except the difference in the winding ratio of the switching transformer T2 and T3. U8:A & U8:B senses the alarm for input over-voltage (-58V) and under- voltage (-40V). U8:A & U8:B senses input for out of limit (-58V & -40V) beyond which the power supply unit is shut off by disabling the switching regulators Ui, U2 & U5 through diodes CR29, CR30 and CR28 for safety of the equipment. U7:A & U7:B senses over-voltage and under-voltage condition for the ±5V power supply. If the output voltage exceeds 6.4V Ki relay is initiated through transistor Q7 to isolate the power supply from the system backplane. The situation is also displayed by DS2 LED. For under- voltage, however, only DS3 LED glows, DS 1 indicates the OK condition of the power supply. U7:C & U7:D similarly senses over-voltage and under-voltage condition for the +1OV supply. If the output voltage exceeds 14V Ki relay is initiated through transistor Q7 to isolate the power supply from the system backplane. The situation is also displayed by DS2 LED. For under- voltage, however, only DS3 LED glows. DS1 indicates the OK condition of the power supply. U9:A & U9:B similarly senses over-voltage and under-voltage condition for the +80V supply. If the output voltage exceeds 100V 1(1 relay is initiated through transistor Q7 to isolate the power supply from the system backplane. The situation is also displayed by

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DS2 LED. For under- voltage, however, only DS3 LED glows. DS 1 indicates the OK condition of the power supply. Under voltage alarms of +5V, ±10 & +80V are extended to the processor module to the backplane. The power supply is rated

as follows:

+5V - 3 Amp ±i0v - 0.75Amp +80V - 0.2 Amp

4.5 Network Interface Module

The Network Interface Module primarily takes care of the alarm acquisition function from various internal and external sources and responds to the queries and commands issued by the Network Manager through the “Super-Net” Network Management System. The module runs on a high performance Intel 80C196 microcontroller with associated communication and alarm interfaces for its operation. The block diagram of the Network Interface Module is presented in Figure2. The Network Interface module is used for exchange of information among the Network Manager, the Tributary Module and the various access modules interconnected via the backplane. It has altogether four communication interfaces for information exchange. The network management system is realised through, two serial interfaces, one for external NMS for interfacing the central supervisory computer while the other is used for realising the NMS through the unused National bits of the -2 Mb stream. Other than these, the tributary unit is interconnected through a serial link while the access modules are interfaced through another serial bus. Communication for Network Supervision and Parameter uploading! Downloading is done through a standard 1EC65 frame format whose structure is as shown below.

The structure has been adapted for all transmission equipment of WEBFIL make so that

the same NMS system may be used to access all types of transmission equipment

manufactured by WEBFIL. The baud rate of this link is 1200 bps and is operated as

digital omnibus link is semiduplex master/slave mode.

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CHAPTER 5: ADVANTAGES AND DISADVANTAGES

5.1 Advantages of Polythene Insulated jelly Cables:

Counting of pairs is easy and human mistakes are avoided.

Jointing is easy and require no chamber or additional place.

Failure of joints is less.

Entry of moisture / water is prevented by Jelly in the core.

Cables can be directly terminated on MDF / Cabinet / Pillar and DPs, thus

avoiding additional joints decreasing the cost and time.

Handling of cable is easy not delicate like paper insulated cables.

Life of cable is more.

5.2 Disadvantages of Paper Insulated Cables:

Numbering of pairs is in coded form. Require more skill. Color markings also fade with due course of time.

Jointing of cables require skill and perfection is required while plumbing as even a slight pinhole will cause entry of moisture / water and damage all the pairs.

Extra care is required for handling like coiling, uncoiling to avoid damage.

Water / moisture entry will affect the complete cable at once instantaneously.

Termination in cabinet / pillars / DPs and at MDF is very expensive and time consuming & increases number of joints.

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Figure 5.1: PIJF Cable

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Figure 5.2: Layers of Units in PIJF cable

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CHAPTER 6: OPTICAL FIBRE CABLE

6.1 Introduction to Optical Fiber:

Optical fiber is the latest underground cable that is being used extensively in all the networks including long distance trunks, junction circuits and even the local subscriber loops to enhance the data transmission.

The OF cables are detailed extensively in the other modules of the basic course. How ever for academic interest the advantages of OF cables over copper cables are discussed here under

Optical Fibers are non conductive, hence does not require ground and surge suppression

Optical Fibers are immune to electromagnetic interference Un authorized tapping is not feasible. Easily upgradeable to higher bandwidth. Low loss ( 5db per km to < 0.25 db per km on a typical fiber) Long and unrepeated links , hence inexpensive Small light, and hence cost is less and easy for installation. It does not attract lightning, It does not carry electricity hence not hazardous

The Application of the Fiber Optical cable in communications are:

Is the common carrier nation wide networks Inter connecting all Trunk automatic exchanges Inter connecting all the Exchanges. Under sea cable Control systems Customer premises communication networks. SDH systems 8 MB MUX for 120 channels 34 MB for 480 channels 140 MB for 1920 channels

6.2 Construction:

Optical fiber has two layers:

Core made of material with high refractive index.

Outer layer with low refractive index.

The OFC has glass structure, with small size, it transmits light to a greater

distance with small amount of loss which makes it use in transmitting data.

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A core which carries most of light, surrounded by cladding. The core is

usually made of pure glass or plastic.

Cladding which bonds the light, confine it to core surrounded by it.

A substance layer of glass which doesn’t carry light, but adds to the diameter

& strength of fiber covered by primary layer.

A primary buffer containing which provides the first layer of mechanical

protection covered by secondary buffer.

Secondary buffer coating this protects the relatively fragile primary coating &

underlying fiber.

Figure 6.1: Cross section of Optical fiber

6.2.1 Buffer Tube:

It is the first shield protecting fiber from damage.

It can have one fiber or more.

It can be tight buffer or loose buffer.

It is color coded for identification.

6.2.2 Features of Tight Buffer Tube:

Tight buffer’s inner diameter is same as fiber’s outer buffer.

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Each buffer can hold one fiber only.

It can keep the fiber operational despite break, as the fiber is held in position

firmly.

Easy to prepare for and provide connectors/splicing.

Can be installed vertically.

Normal tight buffer tube cables are used in in-door.

6.2.3 Features of Strength Member:

Purpose is to release fiber from mechanical stress during installation/operation.

Following materials are used as strength member:

Flexible aramid yarn

Flexible fiber glass roving

Metal wire

Metal rope made from twisted steel wires

6.2.4 Features of Outer Jacket:

Surrounds the entire assembly of buffer tube or tubes and strength member.

To provide environmental protection to fibers.

Made of PE.

Steel armor is provided for armored cable.

6.3 Strength of Optical Fiber Cable:

While traditional bulk glass is brittle, the ultra-pure glass of optical fibers exhibits

both high tensile strength and extreme durability.

Tensile strength is of the order of 44000 to 60000 kg/sq.cm.

(For copper it is only 7500 kg per square cm.)

6.3.1 Cladding Diameter:

The cladding diameter tolerance controls the outer diameter of the fiber, with

tighter tolerances ensuring that fibers are almost exactly the same size.

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During splicing, inconsistent cladding diameters can cause cores to misalign

where the fibers join, leading to higher splice losses.

6.3.2 Core/Clad Concentricity:

This reduces the chance of cores that do not match up precisely when two fibers

are splicing together.

Tighter core/clad concentricity tolerances help to ensure that the fiber core is

centered in relation to the cladding.

Core/clad concentricity is determined during the first stages of the manufacturing

process.

6.3.3 Fiber Curl:

It is the inherent curvature along a specific length of optical fiber that is exhibited

to some degree by all fibers.

It is a result of that occurs during the manufacturing process.

6.4 Optical Transmission and Reception:

Optical transmission of data requires a source, which convert signal into light

signals, which convert signal into light signals, which is transmitted then the

receiver is present which causes the light signals to be converted into data signals.

Basically fiber technology is based on use of light energy to transmit data.

The encoded data is converted from electrical signals to optical light pulses and

then transmitted through medium to its destination, when they converted back.

In any fiber link there are mainly 3 parts:

Transmitter

Optical fiber

Receiver

CHAPTER7: JOINT AND TERMINATION OF OPTIC FIBER CABLE

7.1 Methods Of Joining Fiber Optic Cable:

There are two methods:

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1. Splicing

2. Connectors

7.1.1 Splicing:

It is a process of connecting two bare fibers directly without any connections.

These are of two types. They are:

Mechanical Splicing:

This aligns the axis of the two fibers to be jointed and physically hold them

together. It is used for temporary splicing of fibers.

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Figure 7.1: Mechanical splicing

Fusion Splicing:

It provides a fast, reliable, low-loss, fiber to fiber connection by creating a

homogeneous joint between the two fibers. The fibers are melted or fused together by

heating the fiber ends typically using an electric arc. Fusion splices provide a high-quality

joint with the lowest loss (in the range of 0.01 db to 0.1 db) and are practically non-

reflective.

Figure 7.2: Fusion splicing

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CHAPTER 8: CONCLUSION

With The Introduction of state of the art technology into the switching and Transmission equipments the faults due to indoor equipment have been reduced drastically increasing in the satisfaction of the customer. But the rate of faults occurring in the external plant is causing worry to the Managers of the plant.

By adopting two methods of

Implementing Pole less External plant Replacement of obsolete / fault prone telephone instruments

These methods have to detected during inspection and implemented by the way of rehabilitation of the external plant, which results in reduction of heavy fault rate in the outdoor network thereby increasing the satisfaction of customers and managers.

By implementing the pole less external plant the overhead section in the outdoor network including poles, AI wire and drop wires will be replaced by a 5 pair underground cable which is proposed to be laid from the nearest Distribution cable to the Guard’s room and terminated at the LJU.

An average of 50 meters of 5 pair cable perhaps have to be laid in the premises of Guard. With in the Guard’s room it may not require digging of trench to a depth of 1 meter and a easy method of laying in cost free earthen or PVC pipes can be laid under the flooring which it self is a mechanical protection. This also reduced cost and easy replacement in future.

Implementation of pole less scheme should be done in phased manner. In order to get quick results in reducing fault rate with minimum expenditure and time, the following points should be kept in mind while identifying the priority area where:

Maximum Over head lines exist Maximum faults are booked and noticed Many overhead bridge with railway track and power crossing exist. DPs are in bad condition due to traffic congestion. Different gauge drop wires exist. Many DPs for which the Phone Mechanic is Removing the pair from DP

termination and twisting the UG cable pair to Drop wire directly. Non feasible areas exist. High telephone density exists

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BIBILOGRAPHY

India Telecom By Information Gatekeepers, Inc.

Electrical Cables for Power and Signal Transmission by Oswald I. Gilbetson.

Underground CABLE FAULT Location by Barry Clegg.

Power and Communication Cables: Theory and Application by R. Bartnikas (editor) and K. D. Srivastava (editor).

High Speed Signal Propagation: Advanced Black Magic by Howard W. Johnson and Martin Graham.

Plastic Optical Fibers: Principles, Components, Installation by Andreas Weinert.

http://www.cablemasterinc.com/

http://www.cablemasterinc.com/

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