Aids Ships In Fog.

New York Times 100 years ago today, August 30, 1912:
English Invention Shows Direction from Which Sounds Are Coming.
Special Cable to The New York Times.
    LONDON, Aug. 29.— A successful demonstration has been made in Liverpool of an invention for the use of ships, particularly in time of fog, to show the direction of sounds, such as those of sirens of other ships.
    The apparatus, which is the invention of two brothers named Hodkinson, consists of a drum to receive the sound waves and an indicator. The drum, which measures 9 feet by 5 feet, is placed aloft, where it cannot he affected by sounds on deck, and is connected electrically with an indicator, which is placed in such a position that it can readily be seen by the ship's officer on duty. The receiver consists of a number of units, each of which receives sound waves from a particular direction. Though sensitive to sound waves, they are not affected by ordinary mechanical vibrations.
    By means of the electrical device a sound wave from a particular direction causes an electric lamp in a particular position in the indicator to be lighted. The position of the lighted lamp shows the position the ship whose siren is sounding occupies with regard to the ship which carries the apparatus. The lamp remains alight until it is seen by the officer on duty, who can then switch it off.
    If the other vessel is moving, different lamps are lighted in succession, showing the vessel's course. The apparatus indicates the direction in which the vessel blowing her foghorn is traveling— whether she is going ahead, astern, or on either side. If there are several ships in the vicinity, the recording lights from any of them can be shut off until the position of the others has been observed.