What is DCS?

DCS or Digital-Coded Squelch superimposes a continuous stream of FSK digital data, at about 136 baud, on the transmitted signal. In the same way that a single CTCSS tone would be used on an entire group of radios, the same DCS code is used in a group of radios. DCS is also referred to as DPL tone (for Digital Private Line, a trademark of Motorola), and likewise, GE's implementation of DCS is referred to a Digital Channel Guard (or DCG).

Some equipment uses a 136 Hz square wave turn off code. The turn-off signal is sent for one- to three-tenths of a second (100-300 mS) at the end of a transmission to mute the audio so that a squelch crash is not heard. Radios with DCS options are generally compatible provided the radio's encoder-decoder will use the same code as radios in the existing system. Codes are usually described as three octal digits, (for example, 054). Some DCS codes are inverted data of others: one code with the marks and spaces inverted may form a different valid DCS code (413 is equivalent to 054 inverted).