Decoding the pulse dialing should be easy enough. If you consider what the mechanism was 40 years ago, i.e. the mechanical central office, with stepping relays which responded to the pulses created by your telephone, it will become obvious that what each number did was drive a stepping relay which selected which bank of relays would be the destination of the next stream of pulses. If you count the pulses, which wil be at either 10 or 20 Hz, depending on the age of the telephone generating them, you'll get the number dialed. count/time the pulses. When one pulse is missing or 10 have been accumulated, go to the next digit ... Certain digits have special meanings, i.e. starting with a '1' meant it should expect a 10-digit number instead of a 7-digit one. A '0' also had special meaning, didn't it? If you poke around in some of the older National Semiconductor data books, there are plenty of circuits which they no longer sell which show details of how many of these functions are created, including the DTMF decoding, etc. EXAR and Signetics published lots of examples also. It's no coincidence that they all sold PLL components. Dick -----Original Message----- From: Arfon Gryffydd <arfonrg(a)texas.net> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, December 01, 1999 9:07 AM Subject: Re: Teleco Question... More on my devious plan....