Squelch Encoding Schemes
Content provided by: FlexRadio Systems Engineering
CTCSS
CTCSS (Continuous Tone-Coded Squelch System), which continuously superimposes any one of about 50 low-pitch audio tones on the transmitted signal, ranging from 67 to 254 Hz, is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel. The original tone set was 32 tones, and has been expanded over the years. CTCSS is often called PL tone (for Private Line, a trademark of Motorola), or simply tone squelch. General Electric's implementation of CTCSS is called Channel Guard (or CG). RCA Corporation used the name Quiet Channel, or QC. There are many other company-specific names used by radio vendors to describe compatible options. Any CTCSS system that has compatible tones is interchangeable. Old and new radios with CTCSS and radios across manufacturers are compatible.
DCS
DCS (Digital-Coded Squelch) superimposes a continuous stream of FSK digital data, at 134.4 bits per second, on the transmitted signal. This data is sub-audible with most of its energy below 300Hz. However is does have a wide bandwidth from 2 to 300 Hz. Unlike CTCSS (Continuous Tone Coded Squelch System) which uses continuous tones below 300 Hz., DCS uses digital data or code words. 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 Digital Private Line (or DPL), another trademark of Motorola, and likewise, General Electric's implementation of DCS is referred to a Digital Channel Guard (or DCG). DCS is also called DTCS (Digital Tone Code Squelch) by Icom, and other names by other manufacturers. Radios with DCS options are generally compatible provided the radio's encoder-decoder will use the same code as radios in the existing system. Be aware that the same 23-bit DCS word can, for example produce three different valid DCS codes.
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| System Dependencies | |
| Minimum PowerSDR Version: | N/A |
| Applicable Hardware: | N/A |
Content provided by: FlexRadio Systems Engineering
CTCSS
CTCSS (Continuous Tone-Coded Squelch System), which continuously superimposes any one of about 50 low-pitch audio tones on the transmitted signal, ranging from 67 to 254 Hz, is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel. The original tone set was 32 tones, and has been expanded over the years. CTCSS is often called PL tone (for Private Line, a trademark of Motorola), or simply tone squelch. General Electric's implementation of CTCSS is called Channel Guard (or CG). RCA Corporation used the name Quiet Channel, or QC. There are many other company-specific names used by radio vendors to describe compatible options. Any CTCSS system that has compatible tones is interchangeable. Old and new radios with CTCSS and radios across manufacturers are compatible.
DCS
DCS (Digital-Coded Squelch) superimposes a continuous stream of FSK digital data, at 134.4 bits per second, on the transmitted signal. This data is sub-audible with most of its energy below 300Hz. However is does have a wide bandwidth from 2 to 300 Hz. Unlike CTCSS (Continuous Tone Coded Squelch System) which uses continuous tones below 300 Hz., DCS uses digital data or code words. 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 Digital Private Line (or DPL), another trademark of Motorola, and likewise, General Electric's implementation of DCS is referred to a Digital Channel Guard (or DCG). DCS is also called DTCS (Digital Tone Code Squelch) by Icom, and other names by other manufacturers. Radios with DCS options are generally compatible provided the radio's encoder-decoder will use the same code as radios in the existing system. Be aware that the same 23-bit DCS word can, for example produce three different valid DCS codes.
This KB article may reference additional files that are available on the FlexRadio Systems web site Downloads page. Please use the URL(s) below to download the referenced materials.
An Adobe Acrobat Reader may be required to open the file.You can download Adobe Acrobat from here.
KB Source Document(s):
None Referenced
