Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!decwrl!llustig!xanadu!jeff
From: jeff@xanadu.com (Jeff Crilly N6ZFX)
Newsgroups: sci.electronics
Subject: getting audio in/out of a phone at line connection
Message-ID: <1991Mar24.082410.13911@xanadu.com>
Date: 24 Mar 91 08:24:10 GMT
Distribution: na
Organization: AMIX Corporation, Palo Alto, CA
Lines: 25

I have an old cordless phone that has problems with it and has been retired.
I want to use it as a remote control for my shortwave radio which has
a serial port on it.  So I figure I can hook the base (the telco line
connection) to a circuit that decodes DTMF signals and uses these signals 
to feed the proper commands to the radio.  The question is: what is the 
circuit that will provide audio from the telco line of the base unit?

As a side note: the phone also doubles as an intercom.  So what I plan
to do is take the audio from the radio and feed it into the base unit's
microphone.  But I think that the DTMF is actually generated by the
base unit and doesn't show up on the intercom speaker; only on the telco
line.

As a second part to the question above: Is there a circuit that can take
audio and feed it *into* the telco connection of the base unit while also
generating the audio from the base unit?  (So I can eliminate using the
intercom mode of the phone.)  

Also, I have no plan to use the phone on real phone lines at the same time.

Thanks

Jeff Crilly
AMIX Corporation  2345 Yale Street  Palo Alto, CA  94306
jeff@markets.amix.com, {uunet,sun}!markets!jeff