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

pulse-code modulation Pulse-code modulation (PCM) is a method used to digitally represent sampled 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 (comp ...

(PCM). He was awarded 82 patents.

Early life

Alec Reeves was born in Redhill, Surrey in 1902 and was educated at the

Reigate Grammar School Reigate Grammar School is a 2–18 mixed independent 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 Jon Will ...

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

Imperial College London Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cu ...

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 shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 m ...

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 mor ...

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 radio telephones. He was also responsible for innovations in the design of automatic frequency control 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 public ...

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. Unfortunately 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 fitting ...

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

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

made it viable, although it was used by

Bell Telephone Laboratories Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

during the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...

for secure communications links, such as the SIGSALY system used for encrypted voice communications between

Roosevelt Roosevelt may refer to: *Theodore Roosevelt (1858–1919), 26th U.S. president * Franklin D. Roosevelt (1882–1945), 32nd U.S. president Businesses and organisations * Roosevelt Hotel (disambiguation) * Roosevelt & Son, a merchant bank * Rooseve ...

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 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 scientif ...

'. Reeves was later transferred to the

Telecommunications Research Establishment The Telecommunications Research Establishment (TRE) was the main United Kingdom research and development organization 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 frequencies to determine a position of an object on the Earth, either the vessel or an obstruction. Like radiolocation, it is a type of radiodetermination. The basic principles a ...

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

, 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 oboe plays in the treble or soprano range. ...

', 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 United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...

, 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 Sir Charles Kao Kuen Charles K. Kao was elected in 1990
as a memb ...

and George Hockham at Standard Telecommunication Laboratories - initially at Enfield, North London, and later at Harlow Essex - which invented optical fibres 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 {{notability, 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 - Geo ...

in 1965 and also the CBE in 1969.

References