[MaeWest]

Surely, somewhere on the web there is a recording of the magic 'beep,beap,bepe' that could be used without hunting for an unused number.
I keep getting spam faxes for "vacation specials". They pretend they are from "corporate travel office" or the HR department passing on a special offer for the employees. They have the same format but with different phone numbers on them. Grrrrrrr.

[taxcontrol]

Here is the link to a web page that tells you how to do this and provides the audio files. It can be done from your PC if you have speakers.

http://www.webwithwes.com/defeat.htm

[freedumb2003]

http://www.payphone-directory.org/sounds/wav/bell/accesscode.wav

This one should work.

That same site has a lot of pretty cool recordings.