Radio beginners often ask questions about CTCSS (Continuous Tone Controlled Squelch System) , thinking that they are vague and difficult to grasp. So today we will talk about what CTCSS is. CTCSS is a technology that adds frequencies lower than the audio frequency (67Hz-254.1Hz) to the audio signal and transmits it together. The purpose is to check whether the signal is legal and whether to respon...