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What is CTCSS (Tone Squelch)?

April 26, 2017ctcss squelch Tone

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What is CTCSS (Tone Squelch)?

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CTCSS stands for Continuous Tone-Coded Squelch System. The principle is that a sub-audible tone is continuously transmitted in addition to the speech (or other) signal. The tones used are below the normal hearing frequency range and do not interfere with the other signal. In the UK these tones may be used instead of a 1750Hz tone to access repeaters. the UK has been divided into 23 areas and a particular tone has been allocated to each area. Those repeaters that support CTCSS will normally send the appropriate letter (designating the tone frequency) in Morse after the repeater call sign. The tones used are a subset of those available and are: Tone letter Frequency (Hz) A 67.1 B 71.9 C 77.0 D 82.5 E 88.5 F 94.8 G 103.5 H 110.9 J 118.