TeleZapper: "The TeleZapper takes advantage of the telemarketers' automatic dialing equipment and uses it against them. The TeleZapper sends out a signal that your phone is disconnected. By 'fooling' the auto dialer into recording your number as disconnected, it removes your name from telemarketers' calling lists. Sales calls are virtually stopped altogether, but all other calls get through trouble-free. Telemarketers are trapped by their own technology!" Bloody brilliant. I wonder if it works.

A reader writes:

TeleZapper works

I've been using TeleZapper for about two months and my unofficial reaction is that it DOES work, and works great. It takes a few weeks for the 'broken number' to propagate but we have seen a marked decrease in telemarketing calls at home.