Squelch mutes background static noise when no signal is present. In the CS-F100 software, you can set the global squelch level. A level that is too low results in constant static noise, while a level that is too high prevents the radio from receiving distant or weak transmissions. Scanning Configurations
The manual clearly states: "The transceiver can be programmed by an authorized Icom dealer using the CS-F100 cloning software." Without the manual’s button diagrams, you can brick the radio's configuration. icom icf121 manual