HAYES— DETECTION OF SUBMARINES. 43 



general be different in this second case so that the binaural part of 

 the compensation will need to be changed to give a binaural center. 



The switching arrangement in the compensator is designed so 

 that whenever the receivers are connected in for cross-compensation 

 a clutch which connects the maximum and binaural parts of the com- 

 pensation is automatically released leaving the binaural part free to 

 turn while the maximum part remains fixed. This clutch auto- 

 matically falls back into position whenever the port or starboard line 

 of receivers is switched to the compensator. 



The direction of a sound source is then determined on the U-3 

 Tube as follows : Connect the receivers in either eel to the compen- 

 sator and make a binaural setting, then connect either the head or 

 tail groups to the compensator and make a second binaural setting. 

 The common angle on the two double scales is the direction. 



The compensator is provided with two electrical filters either of 

 which can be connected in series with the telephones at will. These 

 filters allow all sounds above a certain definite frequency to readily 

 pass but eliminate almost entirely the lower frequencies. One filter 

 limits the passage to frequencies above 450 and the other to those 

 above 900. Very often disturbing noises can be largely eliminated 

 by using one filter or the other without weakening the comparatively 

 high pitched sound from a submarine. 



The U-2 Tube is one of the best listening devices that has thus 

 far been devised. It can readily be installed on any boat without 

 docking, is durable and easily repaired and rapid in manipulation. 

 It can be operated at fairly high speeds because its streamlining is 

 such that it produces very little water noise itself while it can be 

 towed far enough astern to reduce the water noise and other noises 

 on the listening boat to a minimum. It has the longest range of any 

 of the various types of submarine detectors due to the fact that it 

 employs highly sensitive receivers in multiple combination, operates 

 at sufficient depth to largely eliminate surface noises, and at a suf- 

 ficient distance from the listening boat to largely eliminate local 

 noises, and due to its focusing qualities desirable sounds are inten- 

 sified while other sounds are relatively weakened. 



The use of multiple unit electrical lines is not limited to towing 

 devices. As an " on-board " installation the electrical MV has cer- 



