So…youve added yourself to the donotcall registry so you’ve gotten less pesky calls from telemarkters. And those that DO call, you tell nicely to stop or else get fined. However…there are those phone bots that just refuse to do that. The best way to keep that from happening, is to trick the bot into thinking that your phone line…is vacant.
If you record the US special information tone signal for “vacant circuit” bots are supposed to mark that number as invalid and stop trying. Of course…there are 2 problems to this. First…human callers who get your answering machine will be kind of confused. Second…ever get those bot messages from the hospital saying that you have an appointment X at X, please confirm? Well…theres a possibility those bots will also be dissuaded from calling. All in all, if you have a pesky bot that calls ALL the time, its worth a shot to just get rid of it once, and then remove the tone.

Thank you artofhacking. Presenting: US Special Information tone signal: Vacant Circuit