[sci.electronics] getting audio in/out of a phone at line connection

jeff@xanadu.com (Jeff Crilly N6ZFX) (03/24/91)

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