There's actually a more precise spec for the tip and ring voltages. If you really want it, I can look up my old textbooks and give it to you, but first of all, the tip-ring (battery) voltage is -48 volts, where tip is close to ground. The ring voltage is a somewhat larger AC voltage, normally at about 20 Hz centered about RING such that there's about an 80-volt positive going pulse with respect to tip, but symmetical about RING. The actual voltage can vary quite a bit, but at the ends, where it enters your house, tip is AC referenced to earth. That's probably enough info for most purposes. IIRC, the off-hook AC signal (speech) is about 4-8 volts into 600 ohms. That's not terribly precise, but if you need better, I can dig out some references. Dick -----Original Message----- From: Daniel T. Burrows <dburrows(a)netpath.net> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Tuesday, November 30, 1999 9:21 PM Subject: Re: Teleco Question...