The TeleZapper isn't good enough, because it only stops automated dialers in the best case, and doesn't even work for all of those in the worst case.
You should get a Screen Machine. It has the TeleZapper tone functionality, but it also THEN plays a message telling the caller that if they are a soliciter to hang up and take you off their list. By law if you say that, they have to comply. THEN it tells the caller to dial "5" to connect. If the caller dials 5, your phone rings.
I have had one of these hooked up to our phone for about 4 months. In that time, we have not received a single (NOT ONE) soliciter phone call. Before we installed it, we were getting around three a day (while we were home).
Kwad