7370652 telephone controlled switch

8/14/2019 7370652 Telephone Controlled Switch

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Telephone Controlled Switch

INTRODUCTION

Long distance computer communication has become a challenge of the

present day technology. Recently these computer communication networks are also

termed as information networks. Presently there are many information services for

information exchange like Teletex, Electronics mail, ideo teleconferencing, !acsimile

transmission "!#$%, which are &uit efficient but expensive too.

'ut there could be a situation where the terminal from which we want to

down load or upload few lines or files or say information, may be ()!!* from the

mains. Thus all the technologies are failed. #nd this is, where our pro+ect (Telephone

ontrolled -witch* comes into picture.

To establish an interactive link with such a terminal " which may be

placed anywhere in the world %, we have to put the mains ()* and then communicates

with it using /odems on a telephone network. To materiali0e such a system we would

re&uire some circuitry which would receive commands on telephone line and can switch

mains load ()* or ()!!* " i.e. the (Telephone ontrolled -witch*%.

The two ma+or parts of the system are, the hardware configuration and

software design. 1n the subse&uent section we will deal with each block as well as the

re&uired software in detail.

)ur pro+ect is to eliminate the problem by using such a circuitry, which

can switch the remote terminal )2)!! without anybody being present at the remote

location. This aim is achieved by using T- "Telephone ontrolled -witch%.

-.-.3./..E., -hegaon. 4


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The T- "Telephone ontrolled -witch% designed here is capable of

controlling up to eight main powered loads with the aid of commands received via

telephone. #ny tone5dialing "6T/!% telephone set or hand5held tone dialer may be

used to send commands to the switching unit and remotely control a wide range of

mains appliances in and around home, factories, industries etc. This system is designed

to have a personal access code and with system feedback facility.

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SYSTEM BLOCK DIAGRAM AND OPERATION

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OPERATION:

The circuit is connected to the telephone network +ust like any normal

telephone set. )n being called, the circuit waits for predetermined number of ring

signals and then answers the call "electrically it lifts the receiver%. ext it waits for

preprogrammed system access code, which the caller must transmit with the 6T/!

keypad on his telephone.

The unit is capable of switching up to light loads ) and )!!. 'y

virtue of relays, high voltage and currents may be switched, so that loads may include

mains powered ones. Reception of correct system access code is acknowledged with a

short tone, which the caller can here.

UNITS OF TCS :

Ring detector Unit:

The ring detector 9nit consists of a diode bridge, voltage controllers, an

opto5coupler, oltage and some other components. The main function of this unit is to

detect a ringing signal and rectifies it. This rectified signal interrupts controller.

Switching Unit: -

The switching unit consists of a double pole double throw relay the .

This unit switches the in coming Telephone line to the 6T/! decoder after call is

detected.

-.-.3./..E., -hegaon. :


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DTMF decoder Unit ; 5

This unit consists of a 6T/! decoder 1


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section B digital sections respectively are derived from a single mains transformer with

a secondary voltage of 1-.

WORKING :

The incoming call is detected by the ring detector unit, during this period

the relay in switching unit is )!!. ?hen the call is detected, the ring detector unit gives

the 9 controller unit a logic low pulse. #s per the time delay specified in the 9

controller programming, micro controller waits for about 4C57> seconds. 6uring this

period if anyone pick5up the hand set of telephone set, 9 controller stops working and

telephone set can be used in usual way. 1f no one pick up hand set then 9 controller

unit gives the logic high pulse to the switching unit, thus the relay in the switching unit

is made ) B thus the incoming telephone line is connected to the 6T/! decoder.

The 6T/E recorder receives the signals from the line and converts it into e&uivalent :

bit code. These codes are given to the 9 controller unit. The 9 controller unit uses

these code to perform re&uired operation using the software from the memory unit.

?hen a line on the port 7 goes low the driver transistor is switched )!! and thus the

corresponding relay and the load. 1f the line on Port 7 is made logic high, the

corresponding driver transistor is switched ) and thus the relay and the load.

Thus the T- can be used to switch the mains ) and )!! from a

remote location.

-.-.3./..E., -hegaon. A


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-.-.3./..E., -hegaon. =

Circuit Diagram of TCS


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CIRCUIT DIAGRAM EPLANATION

The heart of the circuit diagram, given in fig 4 is formed by an


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#s soon as the relay is turn ) telephone line is connected to decoder 1


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6esign of Power -upply

-ince a power supply is vital part of all electronic system. 1tJs discussion

is necessary. /ost digital 1Js including controller and 6T/E 1- operate on GC

supply and relays operate on 47 supply. -o we are presenting the power supply design

of re&uired specifications. The basic block diagram is as above.

The schematic dia. of circuit is as shown. #ccording to it, 4C5>54C step

down transformer is used to get 47 supply. These o2p of secondary are given to

bridge rectifiers which converts sine i2p into full wave rectified o2p. The filler

capacitors at the o2p of bridge rectifiers are charged to the peak value of rectified o2p

voltage whenever the diodes are forward biased during entire cycle of i2p waveform, the

voltage across filter capacitor is pulsating de that is combination of dc and ripple

voltage from pulsating dc oltage, a regulated de oltage is extracted by regulator 1

=C.

#ssuming drop across each diode as bridge rectifier is >.= . Kence

voltage at o2p of bridge rectifier is nearly e&ual to 47.

This 47 supply is used to power the relays used.

-.-.3./..E., -hegaon. 4>


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#s shown in fig. 1 =C is a GC regulator and delivers o2p current in

excess of 4#.

The i2p voltage re&uired for this 1 is 47 .

The 47 o2p from bridge rectifier is fed to i2p pin of =C.

This regulator gives a regulated power supply of C.

The capacitor at the o2p of =C 1 helps to improve transient response.

Thus we are getting two power supply of GC B G47 from given

circuit design.

LIST OF COMPONENTS :

I!s

14


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Resistors ;

R7, R8, R:, RC@,=

R==.@

RA=.@

R478@

R48A7

R4>

R4@8>>

R44>

R44A

apacitors;

44> !

7, 877 p!

C, A>.>4 !

=, .4 !

-.-.3./..E., -hegaon. 47


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MICRO CONTROLLER UNIT ;

/icro controller 1


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1n addition, the


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PIN DESCRIPTION

#cc

-upply oltage

$nd

3round

Port %

Port > is an pins, the pins can be

used as high5impedance inputs.

Port > may also be configured to be the multiplexed lowered

address2data bus during accesses to external program and data memory. 1n this mode P>

has internal pullups.

Port > also receives the code bytes during !lash programming, and

outputs the code bytes during program verification. External pull5ups are re&uired

during program verification.

Port #

Port 4 is an


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Port $

Port 7 is an


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RST

Reset input. # high on this pin for two machines cycles while the

oscillator is running resets the device.

ALE& PROG

#ddress Latch Enable output pulses for latching the low byte of the

address during accesses to external memory. This pin is also the program pulse input

"PR)3% during !lash programming.

1n normal operation #LE is emitted at a constant rate of 42A the oscillator

fre&uency, and may be used for external timing or clocking purposes. ote, however

that one #LE pulse is skipped during each access to external 6ata /emory.

1f desired, #LE operation can be disabled by setting bit > of -!R

location 'EK. ?ith the bit set, #LE is active only during a /)$ or /)

instruction. )therwise, the pin is weakly pulled high. -etting the #LE5disable bit has no

effect if the micro controller is in external execution mode.

PSEN

Program -tore Enable is the read strobe to external program memory.

?hen the #T


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EA &'((

External #ccess Enable E# must be strapped to 36 in order to enable

the device to fetch code from external program memory locations starting at >>>>K up

to !!!!K. ote, however, that if lock bit 4 is programmed. Ea will be internally latched

on reset.

E# should be strapped to cc for internal program executions.

This pin also receives the 475volt programming enable voltage "pp%

during !lash programming, for parts that re&uire 475volt pp.

)TAL#

1nput to the inverting oscillator amplifies and input to the internal clock

operating circuit.

)TAL$

)utput from the inverting oscillator amplifier.

1n micro controller programming , we are using two special function

reg. i.e. T) B 1E reg.

T*E TIMER CONTROL +TCON, SPECIAL FUNCTION REGISTER

= A C : 8 7 4 >

T!4 TR4 T!> TR> 1E4 1T4 1E> 1T>

'it -ymbol !unction= T!4 Timer 4 )verflow flag. -et when timer rolls from all 4s to >.

leared when processor vectors to execute interrupt service

routine located at program address >>4'h.A TR4 Timer 4 run control bit. -et to 4 by program to enable timer to

controlN cleared when processor vector to execute interrupt

service routine located at program address >>>'h.

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C T!> Timer > )verflow flag. -et when timer rolls from all 4s to >.

leared when processor vectors to execute interrupt service

routine located at program address >>>'h.

: TR> Timer > run control bit. -et to 4 by program to enable timer to countN cleared to > by program to halt timer.

6oes not reset timer.

8 1E4 External interrupt 4 Edge flag. -et to 4 when a high5to5low edge

signal is received on port 8 pin 8.8 " 41T %.lear when processor

vectors to interrupt service routine located at program address

>>48h. ot related to timer operations.7 1T4 External interrupt 4 signal type control bit. -et to 4 by program to

enable external interrupt 4 to be triggered by a falling edge

signal.-et to > by program to enable a low5level signal on external

interrupt 4 to generate an interrupt.4 1E> External interrupt > Edge flag. -et to 4 when a high5to5low edge

signal is received on port 8 pin 8.7 " 1.T> %. leared when

processor vectors to interrupt service routine located at program

address >>>8h. ot related to timer operations.> 1T> External interrupt > signal type control bit. -et to 4 by program to

enable external interrupt > to be triggered by a falling edge

signal. -et to > by program to enable a low5level signal on external

interrupt > to generate an interrupt.

Kence T) register becomes ;

= A C : 8 7 4 >

> > > > > > > 4 O >4K

T*E INTERRUPT ENA-LE +IE, SPECIAL FUNCTION REGISTER

= A C : 8 7 4 >

E# 5 ET7 E- ET4 E$4 ET> E$>

'it -ymbol !unction

= E# Enable interrupts bit. leared to > by program to disable all

interruptsN set to 4 to permit individual interrupts to be enabled by

their enable bits.A 5 ot implemented.

C ET7 Reserved for future use.

: E- Enable serial port interrupt. -et to 4 by program to enable serial

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port interruptN cleared to > to disable serial port interrupt.

8 ET4 Enable timer 4 overflow interrupt. -et to 4 by program to enable

timer 4 overflow interruptN cleared to > to disable timer 4

overflow interrupt.7 E$4 Enable external interrupt 4. -et to 1 by program to enable 1.T4

interruptN cleared to > to disable 1.T4 interrupt.

4 ET> Enable timer > overflow interrupt. -et to 4 by program to enable

timer > overflow interrupt; cleared to > to disable timer >

overflow interrupt.

> E$> Enable external interrupt >. -et to 1 by program to enable 1.T>

interruptN cleared to > to disable 1.T> interrupt.

Kence, 1E register becomes

= A C : 8 7 4 >

4 > > > > > > 4 O


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G010ratio1 of DTMF fr02u01ci03:

6ual5tone5multi5fre&uency "6T/!, also known as touch5tone% are the

audible sounds you hear when you press keys on your phone.

Touch5tone is familiar to many "telephone%, it is a mature technology,

and readily available with off5the5shelf, single5chip, low5cost components. !or these

reasons 6T/! is often used in remote control applications that typically use telephones

1n 6T/! there are 4A distinct tones. Each tone is the sum of two

fre&uencies; one from a low and one from a high fre&uency group. There are four

different fre&uencies in each group.

Phone only uses 47 of the possible 4A tones. )n the telephone keypad ,

there are only : rows "R4, R7, R8 and R:% and 8 columns "4, 7 and 8%. The rows

and columns select fre&uencies from the low and high fre&uency group respectively.

The exact value of the fre&uencies are listed in Table 8 below;

-.-.3./..E., -hegaon. 74

TELEPK)E EP#6 1 6T/! 61#L13


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T#'LE 8; 6T/! Row2olumn !re&uencies

LOW4FRE5UENCIES

R)? Q !REF9E "K%

R4; R)? > A@=

R7; R)? 4 ==>

R8; R)? 7


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ou can see that the 6T/! generated signal is very distinct and clear.

The hori0ontal axis is in samples. The fre&uency of the tone is about 4@>> K0 5 close to

the 4@>A K0 predicted by Table 8 "A@=G47>@%.

G010ratio1 of DTMF Co6i1g

OPTOCOUPLER IC MCT$E

O(tocou(70r 8a3ic3 :

#n LE6 is a light5generating device, and a phototransistor is a light5

sensitive device. onse&uently, if the two devices are mounted close together in a single

light5excluding package so that the LE6 light can fall on the phototransistor face, as

shown in !igure 4, and the device is then connected into the circuit of !igure 7, it will

be found that the conduction current of F4can be controlled via the conduction current

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of the LE6, even though the two devices are physically separated. -uch a package is

known as an optocoupler, since the input "the LE6% and the output "the phototransistor%

devices are optically coupled.

Fig9 #

Thus, in !igure.7 when -?4, is open no current flows in the LE6, so no

light falls on the face of F4 , so F4 is virtually open5circuit and 0ero voltage is

developed across output resistor R7. ?hen -?4, is closed, current flows through the

LE6 via R4,and the resulting light falls on F, face, causing the phototransistor to

conduct and generate an output voltage across R7.

-.-.3./..E., -hegaon. 7:


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Fig9 $

ote that the simple optically5coupled circuit of !ig 7 can be used with

digital input2output signals only, but that in practice the circuit can easily be modified

for use with analogue input2output signals.

The most important point to note about the optocoupler device of !igure

4 is that a circuit connected to its input can be electrically fully isolated from the output

circuit, and that a potential difference of hundreds or thousands of volts can safely exist

between these two circuits without adversely influencing the optocoupler action. This

isolating characteristic is the main attraction of this type of optocoupler device, which is

generally known as an isolating optocoupler.

Typical isolating optocoupler applications include low5voltage to high5

voltage "or vice versa% signal couplingN interfacing of a computer output signal to

external electronic circuitry or electric motors, etc.N interfacing of ground5referenced

low5voltage circuitry to floating high5voltage circuitry driven directly from the mains

# power lines, etc. )ptocouplers can also be used to replace low5power relays and

pulse transformers in many applications.

E70ctrica7 caract0ri3tic3 of o(tocou(70r :

Trans&er ratios;

)ne of the most important parameters of an optocoupler device is its

optocoupling efficiency, and to maximi0e these parameters and the phototransistor

"which usually operate in the infra5red range% are always closely matched spectrally.

-.-.3./..E., -hegaon. 7C


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The most convenient way of specifying optocoupling efficiency is to

&uote the output5to5input current transfer ratio "TR% of the device, i.e. the ratio the

output current "1c% measured at the collector of the phototransistor, to the input current

"1f% flowing into the LE6. Thus. TR O 121!. 1n practice, TR may be expressed as a

simple figure such as >.C, or "by multiplying this figure by 4>>% as a percentage figure

such as C>S.

Fig9 %

-imple isolating optocouplers with single5transistor output slaws have

typical TR values in the range 7>S to 4>>SN the actual TR value depends "among

other things% on the input and output current values of the device and on the supply

voltage value of the optotransistor. !igure 8 shows three typical sets of output 2 input

currents obtained by different c values.

"ther para'eters :

)ther important optocoupler parameters include the following.

Isolating #oltage :

This is the maximum permissible 6 potential that can be allowed to

exist between the input and output circuits. Typical values vary from C>> to :k.

-.-.3./..E., -hegaon. 7A


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#()MA*+ :

This is the maximum allowable 6 voltage that can be applied across

the output transistor. Typical values vary from 7> to .

I()MA*+;

This is the maximum permissible 6 current that can be allowed to flow

in the input LE6. Typical values vary from :> m# to 4>> m#.

,andwidth :

This is the typical maximum signal fre&uency "in kilohert0% that can be

usefully passed through the optocoupler when the device is operated in its normal mode.

Typical values vary from 7> kK0 to C>> kK0, depending on the type of device

construction.

Practica7 o(tocou(70r3 ;

)ptocouplers arc produced by several different manufacturers. They are

available in a limited number of basic forms, but are retailed under a vast number of

different type numbers. Rather than list all of these types individually, we will simply

look here at typical examples of these devices.

-.-.3./..E., -hegaon. 7=


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Fig9 ;

Practical optocoupler devices are available in six basic forms. !our of

these devices are isolating optocouplers, and the remaining two are the slotted

optocoupler and the reflective optocoupler. The simple isolating optocoupler "!igure :%

uses a single phototransistor output stage and is usually housed in a six5pin package,

with the base terminal of the phototransistor externally available. 1n normal use the base

is left open circuit, and under this condition the optocoupler has a minimum TR value

of 7> S and a useful bandwidth of 8>> kK0. The phototransistor can however be

converted to a photodiode shorting the base "Pin A% and emitter "Pin :% terminals

togetherN under these condition the TR values falls to above >.7 S but the band width

rises to about 8> /K0.

RELAY :4

1n our pro+ect we can use relay as electronic switch to turn ) B )!!

load.

-.-.3./..E., -hegaon. 7


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ust like the normal electrical fitting neutral is connected directly bulb

"or load% and phase connected through switch as shown in fig. b when switch is press ph

is provided to bulb glow.

-ome process we provided directly to device "bulb% and ph connected

to common point connect switch c "normally close% point so Ph is not provided to bulb

and ckt is incomplete so bulb is off but when we set bit "i.e. base of T4% of micro

controller transistor T4conduct and current flowing through coil of Relay and coil get

energi0e so it produce magnetic field across it and pick common point toward )

"normally% open position% so Ph is connected to bulb an its turn ). Like this we can

turn ) and )!! oil devices through relay.

1n our pro+ect ,two types of relays are being used. i.e. -P6T B 6P6T

REL#- # relay makes use of the electric field generated around a conductor carrying

an electric current.

1n a relay thin wire is wound around a soft iron core to become a

powerful electro5magnet. #s current flows though the coil a metal UarmU is attracted by

the magnetic field generated by the coil.

-.-.3./..E., -hegaon. 7@


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A Single Pole, Double Throw - SPDT12 volt relay.

This relay would be described as SinglePole, Single Throw - SPST (see below).

-witch contacts are arranged on the UarmU so that when the arm moves it

causes the switches to either o(01, or c7o30. )n some relays, as one switch opens

another closes. This type of relay is called a 6ou870 tro


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?hen current to the coil is switched off the magnetic field around the

coil collapses very &uickly. This can cause a phenomenon called -ac= 0mf where a

very high voltage UspikeU is produced of opposite polarity to the current originally

driving the coil. This Ureverse voltageU spike can damage other components used in the

interface.

To avoid this problem a U3ig1a7U diode is connected across the coil of the

relay so that any -ac= 0mfis safely UshortedU out and never reaches the rest of the

components.

!low ch"rt #or pro$r"%&

START

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1nitiali0e port P4 and P>

as 12P, )2P port.

6etect arrivalof ringing

signal at

printing if yes

then


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o

es

#

#

-.-.3./..E., -hegaon. 87

Turn ) bu00er and

telephone relay so that

telephone line connected

to 6T/! decodes andwait7> sec

1s 7> sec.

omplete V

Turn off 'u00er and

generate assurance tone for

person at remote location

6etect if 1 to

pin high i.e. data

is available at

)2P of 6T/P

decoder

Read the no. and store no

in memory location


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o

es

o

6 es

E6

C

o

#

es

6

-.-.3./..E., -hegaon. 88

1s store no is

compare with

device 4 no

1s store no is

compare withdevice 7 no

omplement position

of device 4

3enerate assurance

tone for C sec.omplement

position of

device 71s store no is

compare with

device 8 no

omplement

position of

device 8

1s store no

compare with

device : no.

omplement

position of

device :


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PROGRAM FOR TELEP*ONE CONTROL SWITC*

)R3 >>>>KNstart program execution from starting memoryN

Nlocation >>>>K

/P -T#RTN +ump on program start subroutine.

TK1- -9'R)9T1E )/E- 1 P1T9RE ?KE 6#T# 1- ##1L#'LE #T

6T/! 6E)6ER )2P "i.e. ?KE 1T) )9RE- %

)R3 >>>8K Nthis is reserve interrupt memory locationN

Nfor 1T) interrupt

/) #,P4 Nmove data from port p4 to accumulator

Ni.e. store first digit.

6 R=, RE Ndecrement r= register by 4for detection

-.-.3./..E., -hegaon. 8:


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Nof first or second digit.

#66 #,RA Nif this is second digit then add first digit

Nwith second so that complete no. si store in accumulatorNfor comparison

E #, Q 8C K, E$TN compare receive no. with first device no.

PL P7,=Nif comparison is e&ual complement device

-ET' 74KNset bit 74h for assurance tone generation

E$T ; E #,Q8AK,E$T4N compare receive no. with second device no

PL P7.AN if comparison is e&ual complement device

-ET' 74KN set bit 74h for assurance tone generation.

E$T4; E #, Q8=K, E$T7Ncompare receive no. with third device no.

PL P7.ANif comparison is e&ual complement device

-ET' 74KN set bit 74h for assurance tone generation.

E$T7; E #, Q8


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-)96 ; -ET' P8.A NTurn on bu00er

#LL 6EL#7Nall delay

LR P8.AN#fter completing delay turn off bu00er-ET' P8.=Ngenerate assurance tone

#LL 6EL#Ncall delay

LR P>.=Nturn of assurance tone

/) T),Q>4KNset 1T) as low to high trigger pulse

/) 1E,Q.=Nturn on musical 1

#LL 6EL#Ncall delay subroutine

LR p>.= Nturn off musical 1

/P ?#1T N+ump on wait

TK1- 1- 6EL# -9R)9T1E

6EL#; /) R>,Q!!K Nmov R> register with data !!K

-4 ; /) R4,Q!!KNmov R4 register with data !!K

- ; 6 R4,- Ndecrement and +ump if R4 is not 0ero

6 R>,-4 Ndecrement and +ump if R> is not 0ero

RET Nreturn from subroutine

-.-.3./..E., -hegaon. 8A


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Applic"tion'

#, IN LONG DISTANCE COMPUTER COMMUNICATION :

1n such system the information from the remote terminal can be

accessed, using modem and Telephone line. There could be a situation where the

terminal from which we want to down load or upload information may be off from the

mains. 1n such situations dater transfer cannot be possible. This situation can be

avoided by replacing local switch by T-. ?hen terminal is off from mains, this mains

can be switched ) using T- and thus data can be transmitted to modems. # modem

translates information produced by computer into impulses that can be send over regular

telephone line. #t the other end of line, another modem receives these impulses and

-.-.3./..E., -hegaon. 8=


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translates them back into signal that can be understood by computer. Thus T- can be

useful in dong distance computer.

$, IN INDUSTRIES OR PLANTS :

?here the mains switching is re&uired in extreme conditions such as

high conditions "temperatures%, under pressure, gaseous condition or extremely cool

conditions, where human interpretation is not possible.

%, IN SATELLITE COMMUNICATION :

?hen the satellite is set up initially the T- can be used to switch its

various functions. )n such as amplifiers, Transponders etc and get acknowledge even

in difficulty.

:% The most practical example of this system is (Koroscope on telephone*. 1n this the

record of particular WRashiJ is switched ) by dialing particular number after the

telephone number.

C% 1n !ax machine, the !ax machine is re&uired to keep )n constant to receive messages

at any time T- system can be used to switch the !ax machine whenever re&uired and

not at all the time. Thus considerably saving power.

A% -imilarly in /ulti #ccess Rural Radio -ystem "used in rural area for telephone

communication%. ?here the no. of calls are &uite low and power re&uirement is high

and can be switched ) and )!! using T-.

LIMITATIONS ;

4% The main limitation of the circuit is that there is no local control over switching.

-.-.3./..E., -hegaon. 8


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7% The reliability of the circuit is limited by the link via the exchange i.e. the

telephone line should be available on being called.

8% #lthough small, but continue re&uirement of power to the circuitry.

BIBLIOGRAP(Y

-OOKS

4% /icro controller ; The C4 controller by enneth . #yala.

7% oltage regulator manual; ational semiconductors.

8% )pto Electronics ircuit /anual by R./. /arstan, page no. 4>@ to 44C.

:% Elektor /aga0ine, by arel ?alraven, vol. 7>>427>=, une 7>>4.

WE- SITES

www.#tmel.com

www.Teltone.com.
http://www.atmel.com/http://www.teltone.com/http://www.atmel.com/http://www.teltone.com/

7370652 telephone controlled switch

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