call progress decoder problem

[67mb]

I am from the Philippines and getting parts here is difficult. I have built a telephone patch but it stays off-hook if the call was not completed(answered) thus hanging my phone till it is reset manually. I think I can resolve this by detecting the busy tone at the end of the call. I have searched the net and found that the Call progress tone decoder IC may be my answer but we have none of those here in the Philippines. Since a busy signal as I understand has a 0.5sec tone pulse ON and 0.5sec OFF is it possible to make a circuit using common IC like the op-amps or 555timers or ... to detect this pulses to determine that the call was terminated and reset my telephone.

Thanks

arliesantos@yahoo.com

 

[IRstuff]

I think you need to decode the specific tone first, then detect and measure the envelope, which will distinguishe between a regular busy and a fast busy.

TTFN

 

[jbartos]

Suggestion: Visit

http://www.cara.ampr.org/Sop.htm

etc. for more info