Here’s how to emulate the telezapper by using SIT tones on your answering machine or voice mail messages…“Predictive Dialers are used by telemarketing firms to gain more ‘dialing efficiency’. About 75% of junk calls are made with a predictive dialer (PD). One thing a PD does, is monitor what happens when the phone is answered. The Telezapper can emit a ‘disconnect’ tone when your phone line goes off-hook. The tone it transmits is either a single ‘ultra-modulated’ tone or an actual set of 3 ‘Special Information Tones’ (S.I.T.) common to the telecommunications industry: depending on the setting you seletct. It works… now… in some situations. You can get a set of all three Special Information Tones from Private Citizen. Just record the tones at the beginning of your answering machine message and put your greeting right after it.” Link.