Uniden SC200 manual What is Ctcss and CDCSS?

What is CTCSS and CDCSS?

The term “Continuous-Tone-Controlled-Squelch-System” (herein referred to as CTCSS) and “Continuous Digital- Controlled-Squelch-System” (herein referred to as CDCSS) shall define a system where the radio receiver (s) are equipped with tone or data responsive devices which allow audio signals to appear at the receiver audio output, select voice processing such as scrambling, select between voice or data, or control repeater functions, only when a carrier modulated with a specific tone or data pattern is received.

CTCSS and CDCSS are used for many purposes. In many cases, CTCSS and CDCSS 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.” You may also need to have your scanner coded correctly to “hear” the repeater.

CTCSS and CDCSS are also used in areas of high interference where there are several stations with output frequencies in close proximity with one another. When this occurs, you may hear multiple communications at the same time. The stations could even interfere with each other to the point where it is impossible to clearly receive either one. When your receiver, in this case, a scanner, is equipped for CTCSS and CDCSS, you can code each received frequency with a specific CTCSS and CDCSS frequency. Then, when multiple signals are broadcast, you will only hear the transmission with the CTCSS tone or CDCSS tone you have programmed. If you do not receive the correct tone with a signal, the squelch of your scanner remains closed and you will not hear anything.

Establishment of the CTCSS tone and CDCSS tone for each transmitter (or repeater) is usually done through the cooperative setting of standards by local frequency allocation groups.

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