Alec Harley Reeves (10 March 1902 – 13 October 1971) was an English scientist best known for his invention of

pulse-code modulation Pulse-code modulation (PCM) is a method used to digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amplitud ...

(PCM). He was awarded 82 patents.

Early life

Alec Reeves was born in

Redhill, Surrey Redhill () is a town status in the United Kingdom, town in the borough of Reigate and Banstead within the county of Surrey, England. The town, which adjoins the town of Reigate to the west, is due south of London Borough of Croydon, Croydon in ...

in 1902 and was educated at the

Reigate Grammar School Reigate Grammar School is an 11–18 co-educational private day school in Reigate, Surrey, England. It was established in 1675 by Henry Smith. History The school was founded as a free school for poor boys in 1675 by Alderman Henry Smith with Jo ...

, followed by a scholarship to the City and Guilds Engineering College in 1918, and then postgraduate studies at

Imperial College London Imperial College London, also known as Imperial, is a Public university, public research university in London, England. Its history began with Prince Albert of Saxe-Coburg and Gotha, Prince Albert, husband of Queen Victoria, who envisioned a Al ...

in 1921.

Career

Reeves joined the International Western Electric Company in 1923, and was part of a team of engineers responsible for the first commercial transatlantic telephone link. In 1925 Western Electric's European operations were acquired by ITT, and in 1927 Reeves was transferred to ITT's research laboratories in Paris. Whilst in Paris, he was responsible for a number of projects, including: a

short-wave radio Shortwave radio is radio transmission using radio frequencies in the shortwave bands (SW). There is no official definition of the band range, but it always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (app ...

link between the

telephone network A telephone network is a telecommunications network that connects telephones, which allows telephone calls between two or more parties, as well as newer features such as fax and internet. The idea was revolutionized in the 1920s, as more and more ...

s of Spain and South America, the world's first single-sideband radio telephone system, and for developing a multi-channel carrier system for

UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter ...

radio telephones. He was also responsible for innovations in the design of

automatic frequency control In radio equipment, Automatic Frequency Control (AFC), also called Automatic Fine Tuning (AFT), is a method or circuit to automatically keep a resonant circuit tuned to the frequency of an incoming radio signal. It is primarily used in radio re ...

circuits, digital delay lines and

condenser microphone A microphone, colloquially called a mic (), or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publi ...

Pulse Code Modulation

Reeves recognised the potential that

had for reducing noise when speech is transmitted over long distances. With an analogue signal, every time the signal is amplified, the noise contained in the signal is also amplified and new, additional noise is added. With pulse code modulation, all that is required is to regenerate the pulses, hence the noise content of the signal is not increased. Reeves patented the invention in 1938. However, his idea required quite complex circuitry (by 1930s standards) that was not cost-effective using

valves A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, ...

. Pulse code modulation was not used commercially until the 1950s when the invention of the

transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

made it viable, although it was used by

Bell Telephone Laboratories Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, Murray Hill, New Jersey, the compa ...

during the

Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

for secure communications links, such as the

SIGSALY SIGSALY (also known as the X System, Project X, Ciphony I, and the Green Hornet) was a secure voice, secure speech system used in World War II for the highest-level Allies of World War II, Allied communications. It pioneered a number of digital co ...

system used for encrypted voice communications between Roosevelt and Churchill.

World War II

Following the invasion of France by Germany in 1940, Reeves escaped over the Spanish border and then made his way back to England aboard a cargo ship. He joined the

Royal Aircraft Establishment The Royal Aircraft Establishment (RAE) was a British research establishment, known by several different names during its history, that eventually came under the aegis of the Ministry of Defence (United Kingdom), UK Ministry of Defence (MoD), bef ...

at Farnborough and took part in the development of countermeasures against the German radio navigation systems, the so-called '

battle of the beams The Battle of the Beams was a period early in the Second World War when bombers of the German Air Force (''Luftwaffe'') used a number of increasingly accurate systems of radio navigation for night bombing in the United Kingdom. British scientific ...

'. Reeves was later transferred to the

Telecommunications Research Establishment The Telecommunications Research Establishment (TRE) was the main United Kingdom research and development organisation for radio navigation, radar, infra-red detection for heat seeking missiles, and related work for the Royal Air Force (RAF) ...

as part of a team of scientists and engineers developing Britain's own

radio navigation Radio navigation or radionavigation is the application of radio waves to geolocalization, determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of Radiodetermination-satellite servi ...

aids. The first system they developed was called ' GEE', a system that performed well, but was susceptible to jamming and was not accurate enough for blind bombing of targets at night or through thick cloud. Together with Frank Jones of the Telecommunications Research Establishment, Reeves developed a new system called '

Oboe The oboe ( ) is a type of double-reed woodwind instrument. Oboes are usually made of wood, but may also be made of synthetic materials, such as plastic, resin, or hybrid composites. The most common type of oboe, the soprano oboe pitched in C, ...

', which offered pin-point accuracy to within 50 yds (45m), and was resistant to jamming. 'Oboe' was to prove invaluable to the

Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...

, during

Bomber Command Bomber Command is an organisational military unit, generally subordinate to the air force of a country. The best known were in Britain and the United States. A Bomber Command is generally used for strategic bombing (although at times, e.g. during t ...

's offensive against Germany.

Post War

After the war, Alec Reeves managed a team led by Charles K. Kao and George Hockham at Standard Telecommunication Laboratories – initially at Enfield, North London, and later at Harlow Essex – which invented

optical fibre An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...

s as a means of communicating large quantities of information. Kao was awarded the 2009 Nobel Prize in physics for his part in this achievement. Reeves worked at STL until retirement. He was awarded the

Stuart Ballantine Medal {{Refimprove, date=February 2018 The Stuart Ballantine Medal was a science and engineering award presented by the Franklin Institute, of Philadelphia, Pennsylvania, USA. It was named after the US inventor Stuart Ballantine. Laureates *1947 - Ge ...

in 1965 and also the CBE in 1969.

References