The squelch mutes the receiver when the received signal is too weak (e.g., if the transmitter is switched off), preventing the related unwanted noise or, when the transmitter is switched
off, the self-noise of the receiver from becoming audible. If extraneous interference becomes audible, the squelch control is set too low. Turn it up just enough for the receiver to mute.

IMPORTANT: Under normal operating conditions, i.e., in the absence of extraneous interference, always set the squelch control to "MIN." so you can utilize the full sensitivity of the receiver.