Page:Popular Science Monthly Volume 88.djvu/835

 Popular Science Monthly

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���In order that a submerged submarine may direct its course accurately toward a hostile ship it may be provided with microphones on its port and starboard bows. The difference in the volume of sound received by the two microphones indicates the course to be pursued. The sound can be converted into movements of a finger playing over a dial

��posed to the vibrations. At once electrical circuits are closed and auto- matic mechanism started which swings the rudders of the torpedo and points the nose of the torpedo toward its mark. As soon as the microphones on both sides are restored to electrical equilibrium, in other words as soon as they hear with equal clearness, the torpedo keeps on a straightaway course.

It is evident that the same principle can be applied to submarine boats travel- ing under water, with the difference that since the submarine is manned by intel- ligent human beings, the microphones can be made merely to indicate the course to be pursued, leaving to the commander the task of steering a true course. As in the case of the sound- controlled torpedo, the submarine is provided with microphones on its port and starboard bows. Telephone ear- pieces are provided which enable the sub- marine commander to listen to the sounds gathered by the microphones. If the submarine is not pointed head on

��toward the ship to be destro\"ed the microphone on the off side will hear less than the other, and the difference in the \olume of sound received by the two microphone detectors will be noted at once in the telephone receivers. The commander changes his course until he hears equally well with both ear-pieces.

Seeing Sounds on a Dial While it is perfectly feasible to direct a submarine by telephone it is much more effective to convert the microphone vibrations into visual signals. As a result the commander of a submarine has only to watch a finger move over a dial in order to know what course he should steer. In a sense he sees the sound which the microphone detectors hear. The accompanying diagram sets forth the essential principles of this con\'ersion of the microphone vibrations into visual signals so clearl>- that an extended description seems hardly neces- sary.

While a visual steering indicator is

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