Each radio has one assigned, that is included in the transmission. The MPSCS format is ZCCUUUU, where Z is the zone of the system that is the radio's home area, CC is the county, and the UUUU is the unique four digit for that radio. (There are many radios in SEMI that have a 9 for the zone, due to running out of numbers in zone 2. There are some dispatch centers that show 00 as their county, like HVA, as they are connected at the microwave level.)What's a radio ID and how do you access it?