DCS Archives - Two Way Radio Community

DCS CDCSS or Digital Code Squelch (DCS) is a further development of the continuous tone-coded squelch system or CTCSS that uses a slow-speed, binary data stream passed as sub-audible data along with the transmission. Motorola calls this Digital Private Line or DPL. It consists of a 23-bit telegram sent repeatedly on the channel at 134 bits per second along with the voice transmission. This allows for over 100 possible fleet codes to be used. This gives it an advantage over the CTCSS tones in that there are more possible codes to use; however, it does use more bandwidth and can be affected by voice tones below 300 Hz if not properly filtered by the radio circuitry. DCS Codes Below …

CTCSS? DCS? Sub-channels? Yes, Continuous Tone Coded Squelch System. Introduced by Motorola in the early 1960s, as “Private Line” (also known as GE/Ericsson’s “Channel Guard”, E.F. Johnson’s “Call Guard”, RCA’s “Quiet Channel”), known by many as simply “tone squelch”. This is like a mains hum on the modulation, a constant musical note… almost as if someone is standing by you humming as you talk. The receiver can be set to only open its squelch if this tone is received. Any interference would not have the correct tone present, and so the radio would remain quiet. CTCSS was developed into a system with numerous standard tones to choose from, often 38. When CTCSS is used, the audio is filtered out below…

DCS

Digital Code Squelch

Differences between CTCSS and DCS