Telephone Audio Interface

[ugly_guitar_guy]

Hello everyone. I've been building guitar effects pedals and such on an off for a couple of years now. I work in sales and am in need of an audio interface for my telephone to be able to output from, like this one:

http://www.turneraudio.com/jkaudioquicktapifb.aspx

I don't know how phone wires correlate to regular audio, but I do know would like to build this little interface for significantly less than $120 I can buy it from these guys for. Can anyone lend help or refer me to a schematic so I can built a similar unit? Thanks!

[crochambeau]

The wires where that thing is designed to go have direct correlation to audio, low level speaker for your earpiece and microphone level signal for your mouthpiece.

So, imagine each line running through an audio isolation transformer (and you don't need stellar quality here, remember that telephony bandwidth is, well, laughable; so you'd be fine with something spec'd out at 100-4000 hz), feed your secondaries into some resistive or transformer coupled summing and wire it up to an output jack.

Regarding schematics, no idea.
Phones are different from one another in that area, depending on what you have (electret, crystal, etc) so a bit of experimentation may be in order.

Wire in a buffer and run the xformers in parallel if you are afraid of losing quality.