The dual push-to-talk difference
the gp399 "frequency a" and by pushing down you can transmit on "frequency b". frequency a or b can also be used as a scanner of channels, frequencies, ctcss and dts tones.
versatile radio for amateur use
the motorola gp399 is legal for use on amateur frequencies. the gp399 is able to transmit on narrowband (12.5khz) and wideband (25khz).
dual watch receiver
the motorola gp399 has one built-in receiver but can "watch" two channels (semi duplex). monitor two different frequencies (even on different bands (vhf/uhf)) and the radio will monitor both frequencies giving priority to the first station to receive an incoming call.
fm broadcast station
you can listen to the fm broadcast radio, while still monitoring your radio frequencies in the background. any incoming call will be