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ECHO SOUNDING 



5542 



and to notify the officer-in-charge if there is any appreciable change, so that an appro- 

 priate entry may be made in the Record. 



5542. Dorsey Fathometer No. 3 



The Dorsey Fathometer No. 3 is designed for sounding in any depth of water and 

 has three separate dials for use in different depths; and two of these are provided with 

 circuits such that signals are transmitted only on alternate revolutions of the index. 

 This design requires five separate photoelectric tubes and exciter lamps which are 

 connected with separate keying circuits in which the lag may be slightly different, mak- 

 ing the instrumental error different for each circuit. These five circuits are controlled 

 by the depth-selector and starting-frequency switches and each is provided with a 

 separate adjustment. These adjustments are inside the indicator cabinet, and their 



FiQUEK 111. — Location of the index adjustments, Dorsey Fathometer No. 3. 



positions are shown in figure 111. The identity of these adjustments with their 

 corresponding circuits is as follows: 



Knob A controls the position of the index of the 20-fathom dial. 



Knob B controls the position of the index of the 20-fathom dial when alternate signals are deleted. 



Knob C controls the position of the index of the 100-fathom dial. 



Knob D controls the position of the index of the 100-fathom dial when alternate signals are deleted 



Clamping screw E must be loosened to adjust the index of the 1,000-fathom dial. 



