Reginald Fessenden
Reginald Fessenden was born October 6, 1866, in East-Bolton, Quebec, the eldest of the Reverend Elisha Joseph Fessenden and Clementina Trenholme's four children. Elisha Fessenden was a Church of England in Canada minister, and the family moved to a number of postings throughout the province of Ontario.
Fessenden oscillator
A Fessenden oscillator is an electro-acoustic transducer invented by Reginald Fessenden, with development starting in 1912 at the Submarine Signal Company of Boston. 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.