There are three classes of pressure-protected instruments 

 with which you may be reasonably familiar: Man-carrying vehicles, 

 unmanned roving vehicles, and unmanned free vertical-moving 

 vehicles . 



A man-carrying vehicle may be a so-called free instrunnent 

 like the bathyscaphe, Trieste (fig. 3.4 - 3.5), or a cable-connected 

 device like the BATHYSPHERE (fig. 6.3) which preceded the bathy- 

 scaphe by nearly three decades. 



Unmanned, roving, self-propelled vehicles may take the 

 general shape of torpedoes. They may be preprogrammed devices 

 which telemeter information to the surface and are controlled by 

 acoustic telemetry. 



The free vertical-moving instrunnents are designed to collect 

 data as they go down and come back up to the surface without any 

 connecting lines or wires. Some stay on the bottom and collect 

 data and may be recalled to the surface at will. 



In the pressure-equalized category there are a few manned ve- 

 hicles. These include those made for carrying SCUBA divers. 

 The cables of the unmanned cable-connected devices may be either 

 electric or nonelectric. Some unmanned pressure-equalized devices 

 are placed on the bottom. 



Let us examine the effects of pressure on the individual 

 connponents: 



Resistors: The so-called composition types of resistors are in rea- 

 lity excellent pressure gauges which make them particularly 

 treacherous if you haven't had experience. It is necessary to 

 resort either to metallized-film resistors or to wire-wound 

 resistors. Here, if you are being very critical -- though I don't 

 think you need concern yourselves in general with this -- there 

 still is a small pressure effect. 



Capacitors: In general, the nonelectrolytic capacitors do not cause 

 too much trouble. However, depending upon the type employed, 

 one does need to be careful because of the residual space in the 

 cases. Sometimes bubbles are left -- this is troublesome -- or the 

 packaging is otherwise faulty. We have trouble with electrolytic 

 capacitors which we would like to use for coupling transistor 

 circuits. I am not referring to the so-called solid electrolytic types 



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