Here's a quick sound demonstration with the radio.
This tone is found on most, if not all Kenwood radios that have FleetSync. The tone sounds if your radio is setup for FleetSync or MDC-1200 signalling, and if you have it set to send your ID at the beginning of the transmission. The reason it sounds is to let you know the radio is sending your ID and that it's not ready to transmit audio yet. When the tone has sounded, you can speak into the microphone. This tone is not to be confused with the talk permit tone for trunking or conventional, which sounds different.
Back when I was in elementary school, my district was still using First Student as the bus service, and their buses use Kenwood TK-880 radios. I would always remember hearing this tone when the bus drivers keyed up their microphones. The bus company we use now uses these NX-800's along with TK-8180's, all of which use this tone.
