Its the most versatile unit possible. With Ocean Reef GSM Cube3 you are capable of communicating in three different ways: wireless, hard wired, VHF. It can be connected to the ALPHA PRO X DIVERS surface unit for cable hardwired communicationfull duplex, hands free communication. The unit is a permanent wireless unit. Always on receiving mode for any communication on channel 1 frequency. PTT button activates wireless transmission on channel 1. Six-pin waterproof connection permits connecting and detaching from cable communication while underwater. GSM CUBE3 can be connected to a separate unit in order to interface with a VHF radio and permit radio communication while on the surface.