This is something that some of you may find interesting.

In telephony, you might encounter something called Special Information Tones or SIT for short. SIT, according to Wikipedia, are “series of eight, similar sounding ITU-T defined audible signals, each comprised of three audio tones. All SIT signals indicate that a telephone call cannot be completed and are typically followed by a recorded announcement explaining the reason for the call failure.”

Now why should we care about this? This can be very useful, especially if your phone number has become a target from those annoying telemarketers. What you need to do is to play SIT tones at the beginning of your answering machine. Usually a telemarketer phone calls are awaiting for two or three “Hello” answers before playing the recording. But if you put this in your answering machine, their player program will think that your number is no longer in service. Of course, they will have a retry for at least three times before they remove your number from their database for good.

Here’s the standard Special Information Tones:

Alternatively, you can set this as your mobile ringtone if you prefer.