fractions such as half or three-fourths full, etc. The sys- 

 tem operates through a series of three induction coils, one 

 coil in each ballast tub and a reference coil in the conning 

 tower. Comparison of the coil immersed in steel shot with 

 the reference coil which is relatively free of any inductive 

 influence permits the quantities to be read on an instrument 

 within the sphere for each of the tubs. 



Vertical Speed Indicator 



This device is a variable resistance with a spring- 

 loaded vane attached to it. The vane is located on an arm 

 fixed to the conning tower at right angles to the path of 

 travel of the bathyscaph. As the bathyscaph goes up or 

 down, the vane is deflected in one direction or another, 

 varying the resistance in the circuit. This resistance 

 appears on a dial inside the bathyscaph as either ascent 

 or descent, on an empirical scale. 



Directional Information 



Directional information is provided by the use of an 

 electrically driven aircraft gyro. This unit requires 

 400-cycle ac power, and it was necessary to build a small 

 solid state 400-cycle ac inverter for this purpose. Direc- 

 tional information is important on every dive of the bathy- 

 scaph. The steel mass of the sphere and the proximity of 

 operating electrical equipment made the utilization of a 

 magnetic compass entirely out of the question. 



Underwater Telephone 



The underwater telephone on TRIESTE allows its crew 

 to communicate with the surface craft. This unit basically 

 is a voice-modulated sonar. The frequency of the unit is 

 comparable with that of the underwater telephones used in 

 ASW vessels and submarines. The present unit is the 

 second of this type to be designed and built by the Navy 

 Electronics Laboratory for TRIESTE. It operates on 24 

 volts and has a power output of 150 watts (from transducer). 

 Two transducers are fitted to this system, one located on 

 top of the conning tower and the other beneath the float. 

 Transmission may be accomplished either through voice 



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