DTMF.FINAL.doc

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CAMTECH/S/2003/DTMFTE/1.0 1

DTMF TELEPHONE INSTRUMENT

(DESK TYPE 2 WIRE 12 WAY)

1. Brief Intr!"#tin

Desk type, 12 way, 2 wire, DTMF Telephone

instrument is an electronic extended version of

magneto telephone having additional feature of

4 ! push "utton matrix# $t can also "e used as anintercom "etween the su"scri"ers# $t is selective

calling e%uipment used for operation on overhead,

ca"le, microwave or optic fi"er ca"le#

$t is used where the num"ers of points to "e

connected are 4 to 11# $t is also used as an intercom

wherever 4 to 11 parties are re%uired to "econnected for communication# $n &ailways it is used

for point to point communication "etween station

master ' ca"in ()M of a yard* +evel crossing gate,

ca"in ()M ' )tation master*+evel crossing gate,

+evel crossing gate ' ca"in station master, +evel

crossing gate ' +evel crossing gate, ca"in ()M '

a"in ()M etc

This hand"ook contains "rief introduction, various

parts and their function, installation practices,

testing and maintenance of 2 wire 12 way DTMF

telephone instrument according to &D)-

)pecification .o# $&)/ T 0 2#

DTMF TELEPHONE SEPTEMBER2003


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1.1 A!$%nt%&e' $er M%&net Tee*ne

Desk type, 12 way, 2 wire, DTMF Telephoneinstrument replaces magneto telephones with

following advantages/

S. N De'#ritin DTMF Tee*ne M%&net

Tee*ne

1# &inging

)ignal

)tandard DTMF

tones in 3F "and#

igh voltage, low

fre%uency (

signal

2# alling

Facility

5ach telephone has

its own code and can

"e called selectively

from any other telephone

.o selective

calling facility#

!# Transmission

media

(ny media through

which signal can

transmit such as 2

wire over head line,6nderground ca"le,

-ptical fi"er ca"le,

Microwave channel

etc#

2 wire over head

line or

6nderground

ca"le



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4# )elective

calling

(ny of the 12

telephonesconnected in parallel

can "e selectively

called#

.o selective

calling facility#

7# Distance

coverage

Distance having

attenuation up to 27

d8#

+ower distance

since speech

amplifier is notused#

9# )peech

%uality

lear and louder

speech since speech

amplifier is used#

+ow speech since

speech amplifier

is not used#

:# &ing '

ringingconfirmation

&inging "y ;ie


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2. P%rt' + t*eir F"n#tin'

2 wire 12 way DTMF telephone is consisting of thefollowing parts*components#

a> 8ody of the telephone

"> Transmitter and &eceiver

c> ordage

d> ;ush "utton dial

e> 3isual +5D indicationf> ;ower -. +5D indication

g> radle switch mechanism

h> &osette

i> ;ie plastic

material# The colour of the (8) material used for

making the "ody of the telephone is light and in no

case it is "lack#



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2.2 Tr%n'-itter + Re#ei$er

5lectro dynamic transducers are used to perform

functions of transmitter and receiver# Transmitter

converts speech in to electric signal ' receiver

converts electric signal into audio signal#

2. /r!%&e

For connecting handset with the telephone

instrument and telephone instrument with the line#

2.0 P"'* "ttn !i%

)tandard push "utton dial of 4 ! matrix withdigits from to =, B A)tar>, ' C Aash> is provided

on the top cover of the "ody# @hen the push "utton

is pressed, a standard DTMF code*tone is generated

"y code*tone generator#

1 2 .

0 3

4 5 6

7 8 9

RIN:

ON



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reen +5D &ed +5D


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2. ;i'"% LED in!i#%tin

( green +5D for calling attention is provided on the

right side of top cover of the "ody# @hen the press

"utton is pressed for calling, +5D of the called party

is glow# E&ing is printed "elow this green +5D#

2.3 P The handset when resting on the cradle of

completely assem"led telephone shall push

the plungerAs> down to the limits of travel#

ii> The plungerAs> are free and not stick#

iii> The plungerAs> lifting spring is tensioned to

give a positive action#



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iv> andset of the telephone when -. hook or

-FF hook is operates the cradle switch

mechanism, which is checked electrically#

2.5 R'ettee

Telephone rosettee is made of (8)# )uita"le ru""er

grommets are provided on the wire entry holes# Four

way terminal strip is provided inside the telephonerosettee# (ll incoming and outgoing wires of

terminal strip are terminated on screw terminals#

The terminals of 4Gway terminal strip inside the

rosettee are marked for Hve, Gve, and +1, +2#

onnections of telephone instrument strips and

telephone cord are showing "elow#


Ye< :reen Re! B%#=

L1 L2 > ??

TELEPHONE SET ROSSETTEE


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2.6 Pie@ ee#tri# "@@er

5lectric pie


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AIIIII for 1

B Astar> IIIII for 11

C Ahash>IIIII for general code for mastertelephone

$t is possi"le to assign any code to a telephone in

decimal system using ED$;J switches or "y

strapping#

2.11 De#!er

)tandard DTMF decoder is provided# -n receipt of

valid code*tone, it decodes and pie


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2.1 In!"#tin #itr%n'fr-er

old rolled grain oriented silicon steel or ferrite

material is used for core so as to o"tain re%uired

electrical properties# The complete windings are

protected "y proper insulation to avoid ingress of

moisture#

2.10 D/ #=in& #%%#itr

1#7 to 2#2 micro farad capacitor of operating voltage

4 volt minimum is provided for "locking D

voltage on line# apacitor is made of metallised

polyester#

2.1 Ee#tri#% /ir#"it

5lectrical circuit of the instrument is such as

segregate the ringing and speech circuit# $t is

provided with good matching "etween line andinstrument with minimum side tone#



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. Wr=in&

The system is works on voice communication and

signalling on two wire omni"us circuit tapped at

different places for point to point ' multi point

communication#

(s a system, the telephone is used in master ' slave

configuration# There are 1 master and 1 slave

telephones# (ny su"scri"er can "e designated asmaster and others as slaves#

( general call "utton, which is the 12th "utton, is

provided in the master telephone to call all slave

points at a time# -n pressing this "utton, a general

ring will go to the all slave points simultaneously#

eneral ring can "e used "y the master for impartingcertain important instructions simultaneously or for

conference purposes with all parties#

Digit 1 of the matrix is normally used as calling

code for the master telephone and remaining

telephones are assigned other distinct calling digits#

)etting of ringing codes for individual su"scri"ercan "e done "y setting the strips or Dip switches#

The telephone is protected from surge voltages "y

M-3& "ased surge protection system#

The receiver of the telephone instrument is protected

from acoustic shocks "y providing two rectifiers in



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parallel and with opposite polarity across the

receiver#

The current consumption at 12 volt D is not more

than/

2 m( in idle condition#

1 m( during ringing period

7 m( during conversation

.1 Oer%tin

The calling su"scri"er will lift the handset

and press the code of re%uired su"scri"er#

DTMF signal will generate from the

instrument of calling su"scri"er according to

code of called su"scri"er#

-n receipt of valid code*tone, decoder of

called su"scri"er decodes and pie


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&ing "ack tone will feed to the caller,

indicating that called telephone has "een

rung#

The duration of the ringing to call telephone

is normally "e 4 to 7 seconds# $t is possi"le

to send the signalling code even when two or

more parties are in conversation# The

signalling code is transmitted within 7

mili second# 5ven when the "utton is kept

pressed for more than this duration#

+5D of called su"scri"ers telephone will

glow alongwith the ringing of the "u


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0. In'e#tin + Te'tin&

0.1 ;i'"% In'e#tin

The instrument is visually inspected to ensure that

the moulding is free from cracks ' other

imperfections and that all the components are fitted

properly#

0.2 M%r=in&

omplete circuit diagram showing the electrical

connection of the instrument is fixed or printed in

the "ase of the instrument# The colour code of the

wires, value of components and connection to

various terminals are clear indicated#

The following informations are clearly

em"ossed*engraved*screen printed at conspicuous

places/

.ame and*or Monogram of manufacturer

Kear of manufacture

)erial num"er

8atch num"er

)pecification num"er



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0. P%#=in&

The instrument is suita"ly packed so as to avoid anydamage or loss during storage and transport#

0.0 In'"%tin Re'i't%n#e te't

The insulation resistance "etween the "ody and all

terminals of rossettee connected together shall not

less than 7 mega ohm when tested with 7 3 Dmeggar at am"ient temperature#

0. In'ertin L''

$nsertion loss shall not "e more than #7 d8 when

handset of the telephone instrument is on hook

position and shall not "e more than #0 d8 when

handset of the telephone instrument is in lifted

position#


+1 +2 H G

ME::AR5arth +ine


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. In't%%tin Pr%#ti#e'

12 way, 2 wire DTMF instruments are connected on

omni"us circuit tapped at different places for point

to point and multi point communication# (ll

extensions are provided in master slave

configuration as shown "elow#

The instrument shall "e provided nearer or in

front of the su"scri"er for easy

communication#

onnect power supply unit to 2! 3 (, &5D

+5D will glow which indicate the presence of

power supply#

heck whether D output is availa"le at the

out put terminal# $t should 12 volt D LH

2N#


M()T5& 5T5.)$-.)

( 8 D 5 F


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onnect telephone to power supply unit with

proper polarity# ;olarity marking is given in

telephone rosette "ox# $f ( power is notavaila"le, connect any D source of 12 volt#

;ower -. +5D will glow#

onnect line +1 ' +2 to the respective

terminals as marked in rosette "ox#

)et the assigned code "y a D$; switch inside

the telephone#

8e sure that only one D$; code switch is made

-. and all other switches are kept -FF#

The volume level is also ad?usta"le which can

"e set "y strapping provided on the printed

circuit "oard in three steps i#e# low mediumand high#

Test the selfG"low of the telephone instrument#

.ow the telephone is ready for use#



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3. M%inten%n#e

Due to having nonGmoving parts it does not re%uiresmore maintenance# owever, following

maintenance work may "e carried out during routine

visit#

5ach digit of the dialing pad is to "e tested to

ensure their proper function#

leaning of each digit of dialing pad and

terminals of rossettee#

leaning of contact of cradle switch and

replacement of faulty cord#

leaning of dust from microphone and

receiver#

hecking of the receive level and set

accordingly#

hecking of "u


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4. D' %n! Dnt'

D'

6se soft "rush for cleaning the digits of dialing

pad#

For "est result install the unit in a dust free

environment#

(lways terminate "attery terminals in proper

polarity#

Dnt'

Do not expose the instrument to direct sunlight# Do not expose the instrument to extremely

humid condition#

Do not terminate "attery supply in opposite

polarity#

Do not drop the unit on the hard surface#

Do not use any chemical or detergent for clean

the instrument#

(void rough handling*treatment#



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