What function does the tone key squelch provide in a wireless mic system?
Tone key enables the receiver to identify the desired radio signal by means of a super-audible or sub-audible tone that is generated by the transmitter and sent along with the audio signal. The receiver will unmute the audio output only when it picks up a radio signal of adequate strength and it also detects the presence of the tone key. This effectively prevents the possibility of audible noise from the wireless system when the transmitter signal is lost. Turn-on and turn-off delays are incorporated so that the transmitter power switch operates silently, eliminating the need for a separate mute switch. When operating properly, tone key squelch eliminates an audible "pop" when the transmitter is turned on or turned off.
For more information, see the online publication "Selection and Operation of Wireless Microphone Systems".