Brief Description of Tip:3 tones.
Tip on fighting back:
Record the three tones that you get when you dial an invalid number, then put just the first note at the beginning of your answering machine message.
Paul talked to someone at a company that made those autodialers the teleschmucks use. He was told that the autodialer listens for that note and if it hears it, it immediately hangs up and removes the number from its database. So he screened his calls with the answering machine - and the calls dropped way off, though it took a while.
The tones are here, for anyone who wants to try it: