24 



HAYES— DETECTION OF SUBMARINES. 



nect either one of the three pairs of microphone receivers to the two 

 telephone receivers so that not only can the ambiguity in direction be 

 removed, but a pair of receivers favorably oriented for accurate de- 

 termination of direction can be used. 



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Plate IX. Types of microphone circuit. 



This triangular arrangement has been mounted in several dif- 

 ferent ways to meet special conditions. When the three " rats " are 

 mounted on a light frame suspended from a float for use as a drifter 

 set it is termed a " K-Tube " ; when mounted on a streamline frame 

 attached to the deck or keel of a submarine it is called a Y-Tube : 

 when mounted suitably for suspending beneath a light-ship it is 

 termed an " X-Tube " ; when mounted within a tank inside the ship's 

 skin it is termed a " Delta-Tube " ; and when arranged for towing 

 behind a moving boat it is called an " OS-Tube,"' or an " OV-Tube," 

 or an " OK-Tube " depending upon its form. 



The " 3-Spot " in all its forms is an excellent listening device. It 

 is durable, easy to install, determines bearing with considerable ac- 



