For those wondering about CTCS tones (had to remind myself, since it's been a while): > Radio transmitters using CTCSS always transmit their own tone code when

For those wondering about CTCS tones (had to remind myself, since it's been a while): > Radio transmitters using CTCSS always transmit their own tone code whenever the transmit button is pressed. The tone is transmitted at a low level simultaneously with the voice. This is called CTCSS encoding. CTCSS tones range from 67 to 257 Hz. The tones are usually referred to as sub-audible tones. In an FM two-way radio system, CTCSS encoder levels are usually set for 15% of system deviation. For example, in a 5 kHz deviation system, the CTCSS tone level would normally be set to 750 Hz deviation. Engineered systems may call for different level settings in the 500 Hz to 1 kHz (10–20%) range. […] > A CTCSS decoder is based on a very narrow bandpass filter which passes the desired CTCSS tone. The filter's output is amplified and rectified, creating a DC voltage whenever the desired tone is present. The DC voltage is used to turn on, enable, or unmute the receiver's speaker audio stages. When the tone is present, the receiver is unmuted, when it is not present the receiver is silent. * https://en.wikipedia.org/wiki/Continuous_Tone-Coded_Squelch_System https://en.wikipedia.org/wiki/Continuous_Tone-Coded_Squelch_...