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[SOLVED] Play DTMF to already OFF-Hook phone line

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tiwari.aditya13

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Hi

In my setup I have a fixed phone on a telephone line.
I want to connect another 'DTMF generator' to phone line so that i can play DTMF tones..

It will only need to use 'DTMF generator' when my primary phone is off hook.

Is there a way I can avoid a relay in my 'DTMF generator' as it will only be used when line is already in off-hook state?

For above requirement, what if I add a 600 ohm audio transformer's secondaty side in series with the phone line and play
DTMF on it's primary. Will it add a lot of drop to the line.

Regards
Aditya
 

I don't exactly understand the problem. DTMF dialing is always performed in off-hook state.

Besides primary dialing, DTMF tones are often used to control automatic voice mail systems etc. during a call, just pressing dial keys.
 
Dear all, I am new to use the DTMF decoder MT8870D, I have followed what ever there in the datasheet but can not have any output. I have replaced the mic jack with new one. tried calling the phone and answering the call then pressing the keypad from the sender mobile. I still can not find the output.

Please help me figure out the problem. I just need to test the DTMF decoder in order to build mobile controlled appliances.
 

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