TELEMETERING UNDERWATER 



211 



I I I I I 1 I I ' I I I I I I I I I I I I 1 I I I I I I I I 



I I I I I I I I I I L 



Fig. 88. Experimental test of sonic telemetry equipment during Sealab 

 II; all runs at Z20 ft depth and approximately 100 ft from the Sealab 11 

 habitat 



3. Placing of the Receiver on the Staging Vessel 



In Sealab II the receiver and hydrophone were placed in the Sealab habitat. The signals 

 from the receiver were sent topside by a cable system which caused considerable difficulties. 

 Approximately 50 percent of the tests attempted were aborted because of improper connections 

 at the patch panels, intermittent failures in the connectors to these panels, and loss or mis- 

 placement of the cables between the receiver and the patch panels. 



In future operations, these problems should be bypassed by placing the receiver on board 

 the staging vessel. This procedure will eliminate the need for the entire patch- panel cable 

 system (except as a backup) and will also save space in the Sealab habitat. This procedure 

 will also eliminate the work required by the aquanauts of turning the receiver on and checking 

 its operation, etc. (A second hydrophone placed onboard Sealab and connected to the staging 

 vessel by the patch panel will allow reception of signals for testing the gear prior to entry into 

 the water.) This hydrophone will also serve as a backup in case difficulty is experienced with 

 the other hydrophone. 



4. Automatic Receiver and Recorder Operation 



It is a simple matter to design a squelch circuit into the receiver that will automatically 

 activate the recorder whenever signals are being received from the transmitter. In this mode 

 of operation, the receiver can be left on all the time. When it is necessary to record data, the 

 diver will merely have to enter the water. As soon as the receiver detects the incoming signal 

 it will automatically activate the system and record the information, and it will also automati- 

 cally turn off when the diver leaves the water. Provision for bypassing this mode of operation 

 will be provided in the event that it does not function properly. 



5. Future Telemetry Systems 



The following parameters are candidates for the additional channels. 



