Computer Output to Cell Phone Mic Input...

[iBkickinit]

I'd like to make an interface cable so that I can interface a cell phone (or any phone with a 2.5mm jack) with my computer's sound card. Is there any special circuit to do this, or is it just as simple as hooking up the speaker-out to mic-in both ways?

I came across a circuit using some 10K resistors and pots to make a simple mixer so I could combine the computer-out with a microphone which would then feed to the phone. Do I need a special circuit to regulate to volume of the computer-out, or just set it to a particular level?

[Chris Smith]

The best way is to find the impedance of each, and get a matching transformer with those specs.
this way you also get isolation.

[jwax]

No harm in trying the direct connection and see what happens.