The highway patrol uses a duplex channel system, but not in a repeater fashion. It is setup in the same way as the California Highway Patrol, but designates channels numbers in a different way. For instance, Channel 1 and Channel 2 are paired with each other. The odd channels are dispatch to car and car to dispatch with different frequencies. The even numbers are car to car on the dispatch side of the odd numbered channels. For instance, on channel 1, the dispatcher (base) transmits on 42.62 and the car transmits on 42.78 to the dispatcher. Channel 2 is the talkaround (car to car) of channel 1 with a transmit and receive of 42.62. Due to this, you need to monitor the input and output sides of each odd number channel, and the database reflects this. Channel 19 is simplex with the same tx/rx frequencies. NC is planning on turning down the lowband system in favor of VIPER in 2018