- Also see FRS Service & CTCSS for more info on CTCSS Main Menu -

CTCSS/DCS is only used by stations using conventional FM frequency assignments. The original purpose was to allow the sharing of frequencies by more than one fleet - each having their own subaudible tone. Fleets hear only units with their own subaudible tone, and fleets using other tones on the same frequency are not heard. This technology is not used on AM services or in WFM mode. Trunking systems use digital squelch, and do not carry CTCSS/DCS tones. The BC780 merely provides this feature in the modes where it is used, and not in those modes where it is not used in actual practice. The most common use of these tones is NOT for two agencies in the same town to share a frequency, but for different towns within each other's reception range to share one frequency. In tone squelch mode, if you set a CTCSS (Continuous Tone Controlled Signaling System or Continuous Tone Coded Squelch System - analog) or DCS (Digitally Controlled Squelch - digital) subaudible tone for a frequency, the scanner will only stop on that frequency if the transmission includes the prescribed tone. You can also lock a tone assigned to a frequency. By doing this you will receive all transmission on the frequency, regardless of the subaudible tone, except the one which you have locked - any transmissions with that locked-out tone will not be received. You can search for any subaudible tone that is being used on a traqnsmitted frequency (non-truked) by placing the squelch mode into Tone Search. The scanner will check each CTCSS tone sequentially (takes about 15 seconds to go through the whole list) and it will find DCS tones instantly. CTCSS tones are also sometimes called "interference eliminator", coded squelch, Channel Guard, Private Line or PL tones; DCS is also sometimes called Digital Channel Guard, Digital Private Line or DPL tones.. Listed below are the CTCSS frequency in Hz, the EIA Designator, and the Motorola Private Line Designator.