View Full Version : OT: Special Information Tones, DTMF Keypad Sequence

06-07-2012, 04:52 PM
If anyone knows, it will be someone on this board...

Equipment used by telemarketers will automatically disconnect and remove a number from its database if it detects a Special Information Tone (SIT) upon connecting. (I'm sure you've heard it; three tones followed by a recording "We're sorry, the number you have called...)

One strategy that is supposedly effective against telemarketers, including the hated "Card Services", is to preface the message on your answering machine with the three-tone SIT.

Question: Is there a three-key sequence on the phone keypad that generates the SIT, or does it incorporate a different combination of frequencies that are not available from the keypad?

Thanks in advance.

Tony Wells
06-07-2012, 06:03 PM
What you want is the SIT "Intercept" signal. Ref: http://en.wikipedia.org/wiki/Special_information_tones Sound file: http://upload.wikimedia.org/wikipedia/commons/c/cf/IC_SIT.ogg I don't believe it can be created by keypad. Most "Telezapper" type units utilize this technology. I have a spare pc with modem running PhoneTray. It's a free app that handles that for me.

06-07-2012, 06:05 PM
I don't know about a key sequence, but there's a pattern that's supposed to work- it's three tones one after the other, 950 hz, 1400 hz, and 1800 hz. The duration of the tones is 330 ms, with a 30 ms gap between tones. You might look up the tone frequency for each number on the keypad. Once you find that, you would try inputting those when you get a telemarketer call.

06-07-2012, 06:14 PM
Hm- just looked it up. There doesn't appear to be any key which generates those tones- some are close like * and #, but there isn't one for 1800 hz. I would like one that generates the most annoying noise possible at triple the normal volume for the 'enjoyment' of telemarketers :)

06-07-2012, 07:04 PM
Good info. Thanks, all.