A burst of noise (a.k.a. "static") heard after a FM radio transmission ends. The random static sound is actually the radio trying to decipher the ambient background noise into meaningful audio. Usually this noise is hidden from the listener with the squelch function on the radio. In typical squelch systems, the audio circuit is turned off if the radio isn't receiving a signal of a certain minimum signal strength. The squelch tail occurs when the transmission has just ended and the radio circuitry doesn't respond quite fast enough. This is remedied by systems like STE or Squelch Tail Elimination by Motorola which send a brief subaudible tone right before the end of the transmission so that the audio circuit turns off before the modulated signal ends. Creative use of CTCSS like turning off the tone generation circuit on a repeater before the repeater tail will work for radios using tone squelch on both transmit and receive.
by IrishRepublicanArmy December 20, 2003