Understanding.scanning; What Is Ctcss/Dcs - Uniden BC125AT Owner's Manual

understanding.scanning

What is CTCSS/DCS?

Your scanner can monitor systems using a Continuous Tone
Coded Squelch System (CTCSS) and Digital Coded Squelch (DCS)
system, which allows the squelch to open only when the tone
you have programmed with a specific frequency is received
along with a transmission.
CTCSS and DCS are sub-audible tone signaling systems
sometimes referred to as PL or DPL (Motorola's trademarked
terms for Private Line and Digital Private Line respectively).
CTCSS and DCS are used only for FM signals and are usually
associated with both amateur and commercial two-way
frequencies. These systems make use of a special sub-audible
tone that accompanies a transmitted signal.
CTCSS and DCS are used for many purposes. In many cases,
CTCSS and DCS are used to restrict access to a commercial
repeater, so that only those units which transmit the correct
tone along with their signal can "talk" to the repeater.
CTCSS and DCS are also used in areas that receive interference
where there are several stations with output frequencies close
to each other. When this occurs, you might hear multiple
communications on the same frequency. The stations
might even interfere with each other to the point where it is
impossible to clearly receive any of the stations. Your scanner
can code each received frequency with a specific sub-audible
CTCSS or DCS frequency or code. Then, when you receive
multiple signals, you only hear the transmission with the CTCSS
or DCS tone you programmed. If you do not receive the correct
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