LIGHT WEIGHT PORTABLE CONTROL TELEPHONE

Hkkjr ljdkj &GOVERNMENT OF INDIA

jsy ea=ky;& MINISTRY OF RAILWAYS

¼dk;kZy;hu iz;ksx gsrq½& (For official use only)

de otuh lgt oguh; fu;a=.k

nwjHkk"k midj.k

LIGHT WEIGHT PORTABLE

CONTROL TELEPHONE

dSeVsd@,l@2005@ ,yMCY;wihlhVh@1-0 CAMTECH/ S /2005/LWPCT/1.0

uoacj 2005 November 2005

Maharajpur, Gwalior – 474020

Centre

for

Advanced

Maintenance

TECHnology Excellence in Maintenance

CONTENTS

Sr.No.

Description

Page No.

Forward ii

Preface iv

Contents vi

Correction Slip viii

1 Introduction 1

2 Brief Description 2

3 Components 4

4 Working 11

5 Specifications 16

6 Installation 18

7 Operating Instruction 19

8 Maintenance 20

9 Testing 21

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PREFACE

CAMTECH is continuously putting efforts in the

field of documentation & upgradation of information on

Signal & Telecommunication practices. This handbook

has been prepared to help the field staff to help in

installation & maintenance of light weight portable

control telephone equipment.

It is clarified that this handbook does not

supersede any existing provisions laid down in

“Telecom Engineering Manual”, Railway Board

publications and RDSO publications. This handbook is

not statutory and instructions given in it are for the

purpose of guidance only.

We are sincerely thankful to Shri M.K.Yadav,

Director (Tele)/RDSO and field personnel who helped

us in preparing this handbook.

Since technological upgradation and learning is a

continuous process, you may feel the need for some

addition/modification in this handbook. If so, please feel

free to write us. We shall be highly appreciating your

contribution.

CAMTECH A.K.SAGAR

GWALIOR DIRECTOR (S&T)

DATE : 30.11.2005

FOREWORD

It has always been a constant endeavor to utilize

better-upgraded technologies. RDSO has designed light

weight portable control telephone which is not only light

weighted but also can be used on 2-wire as well as 4-

wire communication.

Failure of control telephone may

adversely affect the punctuality of trains. This handbook

covers working, installation, maintenance and operating

instruction of light weight portable control telephone.

I am confident that this book will serve to

enhance the capability and efficiency of the Railway

staff.

CAMTECH R.N. MISHRA

GWALIOR EXECUTIVE DIRECTOR

DATE : 30.11.2005

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ISSUE OF CORRECTION SLIPS

The correction slips to be issued in future for this

handbook will be numbered as follows :

CAMTECH/ S /2005/LWPCTE/1.0C.S. # XX date ------

Where “XX” is the serial number of the concerned

correction slip (starting from 01 onwards).

CORRECTION SLIPS ISSUED

Sr. No.

of C.Slip

Date of

issue

Page No. and

Item no. modified

Remarks

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Hkkjr ljdkj &GOVERNMENT OF INDIA

jsy ea=ky;& MINISTRY OF RAILWAYS

¼dk;kZy;hu iz;ksx gsrq½& (For official use only)

de otuh lgt oguh; fu;a=.k

nwjHkk"k midj.k

LIGHT WEIGHT PORTABLE

CONTROL TELEPHONE

dSeVsd@,l@2005@ ,yMCY;wihlhVh@1-0 CAMTECH/ S /2005/LWPCT/1.0

uoacj 2005 November 2005

LIGHT WEIGHT PORTABLE CONTROL TELEPHONE

1. Introduction

The conventional mode of communication between

driver / guard and section controller is by means of

emergency control Telephone (ECP set). This

emergency communication is initiated from the site

of emergency by drivers / guards of the affected

train. For this purpose driver/guard have to carry

their ECP set to the nearest emergency post which

may be about 500 meters far.

Considering the difficulties in carrying the

conventional emergency portable control

telephone, RDSO laid the specification for light

weight portable control telephone lighter and

handheld for ease of carrying and using.

This handbook covers brief description, various

components, circuit working and installation of the

equipment according to the RDSO specification

no. IRS:TC:78-2000.

CAMTECH/S/2005/LWPCT/1.0

Lightweight portable control telephone November’2005

2

2. Brief Description

The train control is an arbitrary supervision of the

actual movement of the trains between section in

order that section capacity may utilized to the

greatest advantage. This control is exercised by

Section Controller at control office.

Railway control circuits are omnibus telephone

circuits, which provides communication with each

train working point thus facilitating efficient train

operation. They provides satisfactory and reliable

communication between the controller and the

various way side stations, signalling cabins, loco

sheds, yard offices and tapping provided in entire

section.

When control circuits are through under ground

cables, it is difficult to connect a portable

telephones to the control wires to establish

communication between control office and any

point on section. To get over this difficulty taps are

provided from under ground cables at regular

intervals on entire section and these taps are

terminated on sockets.

The control office can be connected by plugging a

telephone in to any of the sockets. These taps are

provided from separate circuit instead of section

control circuit so that the section control circuit is

not un-necessarily disturbed. This speech circuit is

called the emergency control circuit.



3

The lightweight 4 wire/2 wire control telephone

provides communication between any way side

point along the track to section controller in the

control office. This telephone works with two

pencil cells and has facility to communicate both

on RE area and non-RE area selectable through a

sliding switch.

Lightweight portable telephones are provided with

Drivers, Guards and other maintenance staff to

communicate with section controller as and when

required. For communication on 4-wire they

inserts 6 pin plug of his instrument in emergency

socket and establish communication with

controller. Similarly for communication on 2-wire,

both lines of over head control circuit will be

terminated to the terminals provided on the bottom

of the telephone instrument.



4

3. COMPONENTS

Lightweight portable control telephone is consist

of the following components.

Body of telephone instrument

Transmitter

Receiver

Transformer / induction coil

Battery compartment

Battery indication

Cord

Internal wiring Terminals and PCB

DC Blocking Capacitor

Changeover Switch

Six-pin Plug

Battery ON-OFF switch

Press to talk (PTT) switch

Terminal for 2 wire

i) Body of telephone instrument

The body of the Lightweight portable control

telephone instrument is made of mild steel or ABS

plastic. The shape of the body is rectangular box.

The weight of this instrument with all components

except cord and connector is 400 grams in case of

mild steel body and 350 grams in case of ABS

plastic body. The simple sketch of the instrument

is shown below:



5

Battery

Compartment

Hole for Coiled Cord For 2 wire

Line

ii) Transmitter

Electrodynamic transducers /condenser`

microphone/ ceramic microphone is provided as

transmitter. The transmitter is work on 3 volt DC

with associated amplifier for its operation.



6

iii) Receiver

Electrodynamic transducer is provided as receiver.

For the protection against acoustic shock, two

rectifiers in parallel and with opposite polarity are

provided across the receiver.

iv) Transformer / induction coil

Two sets of transformers are provided to match the

transmitter and receiver’s impedance with the line.

Transformers are vaccume impregnated and the

complete windings are protected by proper

insulation to avoid ingress of moisture.

v) Battery compartment

Battery compartment is provided on the

instrument. The cover of this compartment is press

& fit type or screwed flush telephone body. The

Lightweight portable control telephone instrument

is work on 3 volt DC for that purpose two numbers

dry pencil batteries of 1.5 volt are used. These are

housed in a plastic holder fitted with springs to

give proper contact pressure to batteries.

The maximum working current of Light weight

portable control telephone instrument during talk

condition is not more than 15 milli amperes.



7

vi) Battery indication

Dual type LED battery indication is provided in the

front side of the Lightweight portable control

telephone instrument. When battery ON/OFF

switch is put to ON position, green light shall

appear for normal battery voltage and red light for

low battery voltage.

In case of red LED appearing, batteries are

required to be replacing by new ones.

vii) Cord

A cord is provided between 6 pin plug and screw

terminal. This 6 core cord is made of multistrand

PVC insulated wire and not less than 1.5 meter in

length.

Cord’s inserted end is firmly held inside the body

of the telephone instrument so that it can not get

pulled out due to jerks, dangling of the plugs,

repeated usage, rough handling etc.

viii) Internal wiring Terminals and PCB

Glass epoxy PCB of 1.6 mm is used. The PCB is

coated with epoxy base antifungal varnish to

provide protection against dust, humidity, fungal

infection and mechanical abuses.



8

ix) DC Blocking Capacitor

Capacitor made of mettallised polyster is provided.

1.5 to 2.2 micro farad capacitor of operating

voltage minimum 400 volt is used to avoid tripping

of the circuit breaker of the control circuit.

x) Changeover switch

Sliding type switch is provided on the side of the

instrument. It works on one side with 2-wire

control line and opposite side with 4-wire control

line. “2 Wire” and “4 Wire” is printed on the body

to signify the exact position of the switch.

xi) Six pin plug

6-Pin plug is connected with the cord and provided

for inserting in emergency socket. Connections of

six-pin plug’s are such that two outer most pins are

connected on receive, next two on trans and central

two pins are connected to terminals for 2-wire

working.



9

L2

L1

Tx

Rx

Tx

Rx

PLUG CONNECTION DIAGRAM

xii) Battery ON-OFF switch

A sliding type switch is provided on the body of

the Lightweight portable control telephone

instrument for battery make ON or OFF.

This switch is provided in the series with batteries

and extend power to receive amplifier of the circuit

when pressed to ON position. It also extend power

to LED when in the ON position which will glow

to indicate that the telephone instrument is ready

for use.



10

xiii) Press to talk (PTT) switch

Press to talk switch is provided on the body of

lightweight portable control telephone. When this

PTT switch is pressed, it will extend power to trans

amplifier & when released, it will disconnect

supply to this amplifier.

xiv) Terminals for 2 wire

Separate optional terminals at the bottom of the

telephone body are provided for 2-wire connection.

In case if on our requirement these separate

terminals are provided, central two pins of six-pin

plug will be with out any connection. These

separate terminals are banana type terminals.



11

4. Working

Block diagram of lightweight portable control

telephone instrument is given below:

The circuit consisting of electrodynamic inset and

a condenser microphone. In the transpath the

speech output signal from condenser microphone is

low, hence the signal is amplified through an

inbuilt IC amplifier. Another feature in this

telephone is that it has a multi colour LED to

indicate status of battery. A green light indicate

normal condition of battery, red indicates low

battery status.

The wiring diagram and a typical Circuit Diagram

of the instrument manufactured by Epsilon

Electronic Equipment & Components Pvt.Ltd is

shown on next pages.



12

A low voltage IC amplifier U1 is used for trans and

transistor amplifier is used for receive. The trans

amplifier receives the voice from the condenser

microphone and the gain of the amplifier is

adjusted to get 0-dB output across Tx / (L1-L2).



13



14

COMPONENTS – LIST

Part No.

Description

Type

Make

Qty

/Pcs

RESISTORS

R1,R4,R5,R17 1K/ .25W MFR Philips/Keltron 4

R2 680R/.25W MFR Philips/Keltron 1

R3 100K/.25W MFR Philips/Keltron 1


R7,R12 1M/.25W MFR Philips/Keltron 2




R11 56K MFR Philips/Keltron 1



R15,R16 560R/.25W MFR Philips/Keltron 2


CPACITORS

C1, C9 .22MFD/100V PPC Philips/Keltron 2

C2 1MFD/63V Electrolytic Philips/Keltron 1

C3, C10 .1MFD/100V PPC Philips/CTR/FEC 2

C4,C6,C8,C12,

C13

10MFD/25V Electrolytic Philips/Keltron 5

C5 100MFD/40D Electrolytic Philips/Keltron 1

C7 .33MFD/100V PPC Philips/CTR/FEC 1

C11 1.5MFD/400V PPC Philips/Advance 1

DIODES

D1, D2 1N4148 Switching CDIL/ECIL 2

D3 1N4007 Rectifier CDIL/ECIL 1

ZD1, ZD2 4.7V/1WATT Zener CDIL/ECIL 2



15

TRANSISTORS

Q1 TO Q4 2N2222A NPN BEL/CDIL 4

POTENTIOMETERS

P1 20K Multi Turn 3296 Bourns/Spectrol 1

P2 500R Multi Turn 3296 Bourns/Spectrol 1

INTEGRATED CIRCUITS

U1 MC34119 OP-AMP National/Signetics 1

MISCELLANEOUS

RECEIVER RX RT160 RAJAMANI 1

CONDENSER MIC TX CZN-15E SIEMNS 1

SW1 SLIDE SWITCHES GILARD/IEC 1

PTT MICRO SWITCH OEN/IEC 1

PTT BUTTON ----- EPSILON 1

6CORE CORD ------ ASWANI 1

6PIN FLAT PIN ------ EPSILON 1

BI-COLOR LED COMMON CATHOD Fairchild/Quality 1

PC 8 EEE 9935/4 EPSILON 1

EE25 BOBBIN 5 PIN VERTICAL BHAGYA LAXMI 1

EE20 BOBBIN 10PIN VERTICAL BHAGYA LAXMI 1

MOULDED CABINET ABS PLASTIC EPSILON 1

CONNECTORS 6PIN RELAMETE UNICON 1





16

5. Specifications

1. Maximum working current

during talk condition.

< 15 mA

2. Insulation resistance at 500

VDC, between all terminals of 6

pin plug connected together and

the main body.

> 100 Mega Ohms

3. High voltage at 2 KV, 50 HZ

AC sinusoidal r.m.s. when

applied between the body and

all the pins of the 6 pin plug

connect together for one minute.

No breakdown

2 wire side

Send Efficiency

4. Send level –44dBm, 1000 Hz

across MIC with 160 ohms

impedance

> 0dBm (across

line terminals with

600 ohms

impedance)

5. Side tone across receiver < - 18 dBm

6. Total harmonic distortion < 3%

7. Frequency response 300 Hz to

3400 Hz

±0.5 dB

Receive efficiency

8. Receive level –12dBm, 1000 Hz

across MIC with 600ohms

impedance

> -18dBm (across

receiver with 160

ohms impedance)


10. Frequency response 300 Hz to

3400 Hz

±0.5 dB

11. Insertion loss < 0.2 dB listen

condition

<0.8 dB talk

condition



17

4 Wire side

Trans efficiency

12. Send level –44dBm, 1000 Hz

across MIC with 160 ohms

impedance

> +3.8dB (across

Tx terminals

with 1120 ohms

impedance)

13. Side tone across receiver ±0.5 dB


Receive Efficiency

15. Receive level at input of –20

dB, 1000 Hz across mic

terminals with 1120 ohms

impedance

>-26 dBm

(across receiver

terminals with

160 ohms

impedance)

16. Frequency response 300 to 3400

Hz

±0.5 dB

17. Insertion loss < 0.5 dB listen

condition

< 1 dB talk

condition

Dimensions

18. Long 175 mm

19. Wide 50 mm

20. Deep 40 mm

21. Weight 400 gram (max)



18

6. Installation

The lightweight portable control telephone is

supplied duly packed in a waterproof pouch and is

provided with 6 pin plug. Pin configuration is as

given below:

L1 & L2 are available in the centre pins of the plug

as well in the binding terminals provided in the

telephone body. Normally as per the existing

wiring the 2 wire lines are not terminated in the

middle pins of the emergency socket.

Remove the telephone from the pouch and ensure

that 2 numbers of dry cells are inserted in the

battery compartment properly and close the lid.

Switch ON the power by sliding the switch to ON

position. The green LED shall glow. Keep the

second slide switch to 4 wire. The lightweight

portable telephone is ready to use. To talk to the

controller, press the PTT switch. After the use,

power OFF to avoid battery drain and keep the

telephone inside the pouch.

Rx Tx L1 L2 Tx Rx



19

7. Operating Instructions

Keep 2-wire/ 4-wire switch towards 2-wire

side for 2 wire operation and 4 wire side for 4

wire operation.

Insert 6 pin plug in emergency socket for 4

wire operation or connect L1 & L2 to over

head line for 2 wire operation.

Now switch ON the power of the instrument.

Press PTT (Press to Talk switch) to talk.

After conversation switch OFF the power.

If battery indication is RED, replace the

batteries with new one.



20

8. Maintenance

The lightweight portable control telephone

equipment is a solid state, very handy, easy to

operate and maintenance free instrument.

However, following checks may be done for

trouble free operation.

If the power ON LED shows red, the battery

has fallen below 2.7 volt DC. The battery has

to be replaced.

Cleaning of instruments from dust and

moisture.

Continuity of cord.

Since the circuitry works on 3 volts DC and the

operating power is as low as 1mili watt. No

components shall fail. However, while using the

telephone heavy induction due to lightning may

effect the telephone, even though adequate

protection is provided in the line with MOVR and

GD tube.



21

9. Testing

Lightweight portable control telephone instrument

can be tested for insulation and insertion loss tests.

Insulation Test

The insulation resistance between all terminals of

six-pin plug connected together and body of

lightweight portable control telephone instruments

shall not be less than 100 mega ohms when tested

with 500-volt DC meggar at ambient temperature.

Insertion loss tests

2-Wire Listen Condition

It shall not be greater than 0.2 dB.

2-Wire Talk Condition


4-Wire Listen Condition


4-Wire Talk Condition


Documents

LIGHT WEIGHT PORTABLE CONTROL TELEPHONE