The GSM DC™ underwater transceiver unit incorporates the latest innovations in underwater ultrasonic 2-way radio communication. The unit features a digital driver for vocal message equalization, an automatic system for activating transmission (DAT™), and a double transceiver channel.

The GSM DC™ is designed for use on the Neptune full face masks, but can be used on any full face masks equipped with a standard DIN female connection. The standard frequency (channel 1) is the same for all Neptune System units, so it is possible to communicate with any other GSM DC™, GSM DAT™, GSM, M-101A receive units, M-105 Digital surface units, and all previous surface units (M-103, M-104, M-105).

Underwater communication is accomplished through ultrasound and can be used in two unique modes, manual transmission mode and automatic transmission mode. To start communication in manual PTT (Push to Talk) mode, press and hold the “A” button (see picture) to transmit and release the button to receive. The “B” button activates and de-activates the automatic transmission mode, DAT™ (see later). The GSM DC™ automatically begins receiving apabilities
upon contact with the water.