Figure 1. 



A mini-DICORS in use during the range study of 

 diver communication systems. 



Two basic types of communication systems were evaluated; the first group con- 

 sisted of acoustic systems. An "acoustic" system includes a microphone, ampli- 

 fier, power supply, and transducer; it characteristically transduces speech 

 directly into the water by means of the projector (underwater loudspeaker). 

 The signal produced can be received by a hydrophone placed in the water, or by 

 divers without any special receiving equipment. Two of the acoustic systems 

 studied were the Raytheon Yack-Yack and the Bendix Watercom (we had modified 

 the Watercom to enhance its operation) ; both were evaluated in a configuration 

 that included a double hose regulator and Bio-engionics (Nautilus) muzzle. A 

 third "acoustic" system evaluated was the Scuba-com, a mechanical (rather than 

 electronic) unit that consists of a small air filled cavity and diaphragm. 



The second group of communicators consisted of amplitude (am) modulated systems 

 and included the Aquasonics 420, the ERUS-2-3A, the Sub-Com prototype (both 

 short-range and intermediate-range) ^ and the PQC-2. All systems evaluated 

 were rigged with the Bio-engionics "Nautilus" muzzle and a double hose regu- 

 lator. In an AM system, a carrier wave is utilized and is modulated by the 



1 The SCUBA-COM units operate on a slightly different principle but are 

 included in this group for convenience. 



X-3 



