Duddell moving-coil oscillograph with mirror in oil bath, Top-Middle: Rotating shutter and moving mirror assembly used with Duddell oscillograph, for placing time-index marks next to the waveform pattern. Top-Right: Moving-film camera for recording the waveform. Bottom: Film recording of sparking across switch contacts, as a high-voltage circuit is disconnected.

William Du Bois Duddell (1 July 1872 - 4 November 1917) was a British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 electro-physicist and electrical engineer. He was privately educated in the UK and France and rose quickly through the prestigious City & Guilds Schools via scholarships. His inventions include the moving coil oscillograph

Oscillograph

An oscillograph is an instrument for measuring alternating or varying electric current in terms of current and voltage. There are two instruments that are in common use today:*Electromagnetic oscillograph*Cathode-ray oscilloscope...

, as well as the thermo-ammeter

Ammeter

An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes , hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters...

 and thermo-galvanometer

Galvanometer

A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...

.

Prior to the invention of the incandescent light bulb

Incandescent light bulb

The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...

, arc lamp

Arc lamp

"Arc lamp" or "arc light" is the general term for a class of lamps that produce light by an electric arc . The lamp consists of two electrodes, first made from carbon but typically made today of tungsten, which are separated by a gas...

s were used to light the streets. They created light by means of an electrical arc between two carbon electrodes. These lamps also produced a constant audible hum. Duddell was appointed in 1899 to solve this problem. As a result of his research (through which he demonstrated the humming was caused by a fluctuating electric current), he invented the singing arc, which could generate musical notes by way of a keyboard which interrupted oscillations in a circuit, making it one of the first examples of electronic music, and the very first that did not use the telephone system as an amplifier or speaker.

When Duddell exhibited the singing arc to the London Institution of Electrical Engineers, arc lamps on the same circuit in other buildings were noticed to play the tones of Duddell's machine. Despite the potential of music delivered over the lighting network, Duddell did not capitalize on his discovery as anything more than a novelty.

Duddell was made a Fellow of the Royal Society

Royal Society

The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

in 1907.