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Do not connect the chip directly to the phoneline.
Use a small transformer (there are special tranfo's for this) .
Via an optocoupler you can detect if the phone line is open for dialing and then give the DTMF pulses for the number. Via the optocoupler you can detect is the phone at the other site is taken and then you can switch with a relay the line to the microphone and the speaker.
This sequence you can all programm into ths chip.
Succes.
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To be specific to your question
No.
DTMFOUT will just generate a sound of DTMF mixed frequency.
You will have to:
HookOff (if needed)
Wait Dial Tone (about 0.6 sec)
Dial your number
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ok , so how do you electronically hook off then?
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Nothing like detecting dial tone after liftthe telephone (off hook) , before starting DTMF starting. it is only time lag (few hundred mS)after Off Hook.
Regards,
Sarma
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ok but what is off hook.
I mean I have a dual splitter from the telephone line. One line goes to a telephone and the second line will go to the Pic chip. When I need to dial from the chip, how do I do an auto hook off on the telephone line so I can use the DMTFOUT command?
k
Last edited by lerameur; - 10th October 2007 at 20:33.
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As I already told in in the earlier reply, themoment you lift the hanset from the telephone , it is called OFFHOOK. Now in your contest- you may know that the exchange gives a voltage of 48V DC with a max current limit of 35mA. this current will flow thro the switch provided in the instrument. in your case you have to provise a trmnsformer primary loop thro' a relay contact controlled by you . then if the loop is extended , it is called OFFhookOriginally Posted by lerameur
this can be checked by inserting a DMM in DC mA range in series to one of the limbs by breaking the connection and inserting the Meter for current measurement.
Regards,
Sarma
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anybody have a schematic of this?
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