indicator for picup phone on the other side of line

[Uriel]

Hello
i build system that dialing some number with dtmf generator
and i don't know how to detect that after my dialing on the other
side of line answer
so if some of you can help me with ic or schematic circuit
thank you!!

 

[wky]

This is called Off-Hook Dectection.
Try search the web and you could find some circuits for it.

 

[flatulent]

The problem is that the dialing party does not have any indication other than the cessation of the ringing signal sound. The central office does sense this by the flow of current in the line.