HOWTO trick wiretaps into thinking you've hung up

A downloadable MP3 of a C-pitched tone fools many wiretaps into thinking that your conversation has ended, which makes them switch off. If you're worried about being tapped, playing this tone into the receiver might keep your calls a little bit more private. Then again, maybe not.

Download Blaze’s C tone and broadcast it continuously during phone calls. You can play the tone at low volume so it just seems like ambient room noise…

Don’t stop there – befuddle your foes. Play the C for a second in the middle of a call, then without hanging up, dial another number. Analog wiretap systems will interpret this as a new call. You may be chatting with a friend, but now the spooks think you’re talking to Domino’s.

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Update:
Mark sez, "This would be completely ineffective against the most simple and least effective wiretaps like a wireless transmitter or a voice activated tape recorder attached to your phone line."