What sonar device let Morse code messages be sent underwater from a submarine in 1915? – 2017

What sonar device let Morse code messages be sent underwater from a submarine in 1915?



Fessenden oscillator




Reginald Aubrey Fessenden (October 6, 1866 – July 22, 1932) was a Canadian-born inventor, who did a majority of his work in the United States and also claimed U.S. citizenship through his American-born father.[1] During his life he received hundreds of patents in various fields, most notably ones related to radio and sonar.

A Fessenden oscillator is an electro-acoustic transducer invented by Reginald Fessenden, with development starting in 1912 at the Submarine Signal Company of Boston.[1] It was the first successful acoustical echo ranging device. Similar in operating principle to a dynamic voice coil loudspeaker, it was an early kind of transducer, capable of creating underwater sounds and of picking up their echoes.

The creation of this device was motivated by the RMS Titanic disaster of 1912, which highlighted the need to protect ships from collisions with icebergs, obstacles, and other ships. Because of its relatively low operating frequency, it has been replaced in modern transducers by piezoelectric devices.





The device could also be used as an underwater telegraph, sending Morse code through the water. The Fessenden underwater signalling apparatus, or more usually just “The Fessenden”, was fitted to Royal Navy submarines in World War I. British K-series submarines were equipped with Fessenden oscillators starting in 1915. However, a submarine signalling the surface could be heard by any nearby (enemy) hydrophone, so the system had restricted utility during wartime patrols.

The device could also be used as an underwater telegraph, sending Morse code through the water. The Fessenden underwater signalling apparatus, or more usually just “The Fessenden”, was fitted to Royal Navy submarines in World War I.[3] British K-series submarines were equipped with Fessenden oscillators starting in 1915. However, a submarine signalling the surface could be heard by any nearby (enemy) hydrophone, so the system had restricted utility during wartime patrols.

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