Filtered communication

• What is CTCSS? Differences Between Enabled and Disabled Modes

  

  Jun 16, 2026

  What Is CTCSS? CTCSS (Continuous Tone-Coded Squelch System), commonly known as sub-audio code, is an invisible low-frequency signal technology widely applied in two-way radios and wireless communication devices. It serves as a core screening mechanism for frequency signals and plays a vital role in anti-interference and group independent communication. Many global buyers and radio users are confused about the functions of CTCSS and the operational differences between enabling and disabling this feature. CTCSS Working Principle: Lock and Key Analogy To explain this professional technology in a simple and accurate way, we can use the classic lock and key analogy. A single radio frequency channel is equivalent to a public corridor accessible to all nearby wireless devices. In contrast, the C...

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