Digital Coded Squelch

DCS is also known as Motorola Digital Private Line – “DPL “

DCS is a digital form of CTCSS. Instead of sending a continuous audio tone however, it transmits a low level digital signal.

DCS sends a fixed octal digit 4 as the first digit, followed by the three octal digits shown in the table

The code words are 23 bit long strings. 12 bits of octal code followed by 11 bits of CRC. This makes a total of 23 bits sent in a Golay encoded words. There are no sync bits and the baud rate is 134.4. Each bit is 7.5 msec in length, for a total of 172.5 msec. Although it looks like there should be 512 codes available, there are only 83 possibilities. This is to prevent a codeword that is misaligned as it is serially shifted into the decoder, matching one of the other codes.