This shows how to get sound from computer to telephone line. A circuit that would let you connect any Mac to almost any phone circuit.
Original Macs (most compact models, from the 128 up through the SE series) had a low-current audio output jack: it worked well with an amplifier, but didn't have enough oomph [technical term] to drive headphones. So the first circuit I devised just matched that output to the phone system. It wasn't particularly loud, but it worked with any Mac.
Newer Macs have a more powerful output jack. So I modified the circuit to use that power to boost the voltage going to the phone. At the same time, I doubled it so you could use it to pick up both sides of stereo sounds (they'll be mono on the other end of the phone line, of course), or to connect your phone to a stereo amp or tape player.
Which circuit fits your Mac? You can tell by plugging a pair of headphones into the back. If they play in stereo with full volume, use Circuit II. If they sound kind of wimpy, use Circuit I... and dont leave the phones plugged in.
If you've got some other brand of computer, or want to hook your phone to a stereo or other gadget with a headphone jack, one of these circuits will probably still work. But don't ask me for installation advice.
http://www.dplay.com/tutorial/Mac2tel.html
