Hello all

I'm working on a ckt that is connected to the telephone line.The device should be powed by the line itself. The working of the ckt is like , when the telephone is off-hook, the device receives a dtmf sequence, and when it receives the device should respond another dtmf sequence .

The problem is , since the telephone is off-hook , the caller will hear this dtmf handshaking .. Now how to avoid this ?. one way is to connect the telephone through relay(s) operated by the ckt. but i suspect the telephone line cannot supply that much current , and also that is not a good idea..

Any other method to solve this problem

Thanks in advance.
Akg

 

That sounds like a device that could be used in illegal activities. What are you gonna use that for?

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the query was based on a project i got to do..most probably a part of a bigger project and i don't know what the final product is meant for.


Thanks
akg

 

Take a look at the CMX860 (CML Microcircuits). It contains line and phone signal control switching, DTMF generation and detection, FSK Modulator/DeModulator, call progress detection and more.

0x34

 

thanks and let me have a check

 

Quick solution, handshake first then trigger an SCR to connect the handset, will only work if the handset is downstream of your device.

Megamox