PC to Phone Circuit

Thread Starter


Joined Dec 21, 2007
I'm a dummy and I just wanna connect my PC audio to my phone... not to record as everyone else seems to want to do, but to playback a digital recording so I can record it on my voicemail announcement with maximum quality. Holding the phone up to my PC speakers doesn't quite do the job for me :eek:) ... Obviously I'm a little hesitant about hooking the output of my PC soundcard directly to the telephone line because of the power levels and voltages involved with things like the phone ringing. So is there some simple circuit I could connect my PC speaker output to the phoneline and do this with? Or even better a circuit or gizmo that would go both ways so the PC could both record and play over the phoneline? I can read a schematic and assemble a circuit, but analog design is not my strong point :eek:) ... Thanks Y'all!!! and Merry Christmas!


Joined Nov 29, 2005
Get a miniature (or not) audio output transformer canibalizable from an old transistor radio.

Connect the (low Z) 8 ohm winding in series to one of the conductors of the telephone line.
Connect its (high Z) winding to two 1N4004 diodes in reverse parallel and to an either audio source or audio input depending if you want to inject or extract audio from the telephone line.
Adjust audio to a non-distorting needed level.
It is safe, undetectable to the Telco, can be left in circuit forever, will not impair the telephone performance at all.

I do not know how the actual recording of your outgoing message has to be performed, with handset lifted or not.
Lifting the handset will add some ambient noise that you do not want.

Replacing the telephone apparatus with a 200 Ohm half Watt resistor will simulate an off-hook condition and allow clean audio injection.



Joined Jan 10, 2006
Why not use your old twisted pair 56K modem..? There is heaps of software on the net for this