GSM DC Wireless Communication System
The GSM DC™ underwater transceiver unit incorporates the latest innovations in underwater ultrasonic 2-way radio communication. The unit features a digital driver for verbal message equalization, an automatic system for activating transmission (DAT™), and a double transceiver channel. The standard frequency (channel 1) is the same for all Neptune System units, so it is possible to communicate with any other GSM G.divers, GSM DC™, GSM G-Power, GSM G-Power SL, GSM CUBE3, M101A G.divers receive units and M105 Digital / M100 G.divers surface units. The GSM DC™ is a dual channel (DC) unit, which means it is equipped with two transceiver channels. By pressing buttons “A” and “B”, it is possible to change the frequency channel. Any time the channel is changed, a recorded message informs the diver of which channel has been activated (channel 1 or channel 2). The two channels allow different diving groups to operate in the same area with limited interference and confusion. The GSM DC™ sound quality depends upon the D-Mic microphone, a special dynamic microphone with high acoustic qualities, and the microprocessor (DSP), which takes the digitized vocal message and filters out unwanted noise such as exhaust, air bubbles, and/or mask vibrations.
The D-Mic is the special microphone for all OCEAN REEF underwater communication units. The housing has a hydrophobic membrane which is permeable to air, but prevents water from passing through the electronics. The membrane’s reduced thickness limits any reduction of the vocal signal. The permeability of the membrane keeps the internal pressure equalized with the external pressure, enabling the microphone to be used at practically any depth. The D-Mic is installed onto the transmission button contacts and can be made compatible with all previous GSM versions by slightly altering the transmission button contacts; this can be performed at any OCEAN REEF service center. When speaking inside a full face mask, a series of reflections and vibrations, called distorted frequencies, are generated. “High frequencies” are caused
by mask visor vibrations. “Low frequencies” are caused by the noise from air bubbles. If they are not removed, these distorted frequencies will be amplified and transmitted to the receiver unit, resulting in low intelligibility. Our DSP microprocessor removes these frequencies making communication loud and clear. The GSM DC 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 capabilities upon contact with the water.
DAT (Digital Activation Transmission)
This automatic activation system is an exciting innovation in underwater communication exclusively from OCEAN REEF. The DAT™ system allows the option of transmitting in a hands-free mode rather than manual mode. To activate transmission, quickly press and release the “B” button. Once the button is pressed, a series of impulses are sent out, automatically keeping the unit in transmit mode for 30 seconds. After the initial 30 seconds of transmit mode, the unit will return to receive mode for 20 seconds accompanied by a series of impulses in a different tone from the first. This cycle continues until the “B” button is pressed for at least one second, which returns the unit to manual mode. DAT™ is useful when it is necessary to have both hands free while transmitting, making diving more comfortable and safe. Another benefit of the DAT™ system comes in the case of an emergency; by activating the DAT™ a series of impulses will emit every 30-20-30 seconds, which can be received at a great distance by search and rescue workers and other divers.
NACS (Neptune Adjustable Communication Support)
The patented NACS™ is an adjustable support arm for the GSM G.divers, GSM DC™, GSM G-Power, GSM CUBE3, ALPHA PRO, UWCP or M101A G.divers receiving unit. It is installed on the Neptune mask on the left side of the visor and prevents the communication unit from hanging on the mask strap. By relieving the weight of the communication unit, the NACS™ also allows the mask strap to slide easily through the buckle; thus, the strap can stay loose while the mask is donned and the communicator stays out of the way. The NACS™ can be adjusted for tilt and distance between the communication unit and the visor. All GSM models must be used with the NACS™.