The GNC-255's Com radio operates in the aviation voice band, from 118.000 to 136.975 MHz, in 25 kHz steps (default). For European operations, a Com radio configuration of 8.33 kHz steps is also available. The GNC-255 VHF Nav receiver operates from 108 MHz to 117.95 MHz decoding both the VHF Omni Range and Localizer navigation signals. The built-in Glideslope receiver will automatically tune the corresponding glideslope paired frequencies (328 MHz to 335 MHz) when the localizer is tuned. The GNC 255 is available in 10 and 16 watt com transmitter versions. The GNC 255A is available with a 10 watt com transmitter. The GNC 255B is available with a 16 watt com transmitter.