William Duddell

William Du Bois Duddell (1 July 1872, Kensington, London – 4 November 1917, Wandsworth, London) was an English physicist and electrical engineer. His inventions include the moving coil oscillograph, as well as the thermo-ammeter and thermo-galvanometer.

Duddell was born William Du Bois to Frances Kate Du Bois, whom married George Duddell in 1881.

Duddell was privately educated in England and France and rose quickly through the prestigious City & Guilds Schools via scholarships. At the age of four he constructed an automaton by combining a toy mouse with a clockwork.

He died at the age of 45.

Prior to the invention of the incandescent light bulb, arc lamps were used to light the streets. They created light using an electrical arc between two carbon electrodes. These lamps often produced audible humming, hissing, or even howling sounds. In 1899 Duddell, a student of William Ayrton at London Central Technical College, was asked by Ayrton to look into this problem. The sounds were created by instabilities in the current caused by the arc's negative resistance. Duddell connected a tuned circuit consisting of an inductor and capacitor across an arc. The negative resistance of the arc excited audio frequency oscillations in the tuned circuit at its resonant frequency, which could be heard as a musical tone coming from the arc. Duddell used his oscillograph to determine the precise conditions required to produce oscillations. To demonstrate his invention before the London Institution of Electrical Engineers, he wired a keyboard to produce different tones from the arc, and used it to play a tune, God Save the Queen making it one of the first examples of electronic music. This device, which became known as the "singing arc", was one of the first electronic oscillators.

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