Alec Reeves
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Alec Reeves (10 March 1902 - 13 October 1971) was a British scientist best known for his invention of pulse-code modulation (PCM).
Reeves was born in Redhill, Surrey. His father Edward was surveyor to the Royal Geographical Society.
Alec studied engineering at Imperial College London and in 1923 joined International Western Electric, a leading manufacturer of radio and telecommunications equipment. In 1925, the firm was taken over by Sosthenes Behn's International Telephone and Telegraph Company (ITT) and Reeves went to work at ITT's laboratory in Paris, LMT. Here he worked with engineers like Maurice Deloraine and Henri Busignies (who later developed the HF/DF - 'Huff Duff' - system for detecting enemy submarines). Reeves and his colleagues built the first radio-telephone links across the English Channel and the Atlantic. Reeves also perfected the condenser microphone and made major advances in the use of single sideband transmission for short-wave radio.
Reeves appears to have had an enjoyable time in Paris. He later claimed he had played in the French Open tennis championships - which were indeed 'open' to anyone who wished to participate. He is reported to have been seen on the roof of the LMT building conducting paranormal experiments - though one report said he was 'measuring moon-beams'. His private notebooks record a profound interest in Spritualism and regular communication with a ‘spirit guide’ - an American Indian called Red Cloud. Reeves also told friends he was in constant communication with the nineteenth century scientist Michael Faraday.
Invention of pulse code modulation
It was in Paris that Reeves had the idea that made him famous - and which helped shape the modern world. Since the invention of the telephone by Alexander Graham Bell in 1876, speech had been transmitted as a continuously varying wave of electrical energy. But 'analogue' systems have a big weakness: they amplify noise and errors as well as the original message. Reeves proposed a radical alternative. Instead of sending Bell's 'voice-shaped current', he proposed that the sound be sampled at regular intervals. The values of these samples would be represented by binary numbers and transmitted as unequivocal on-off pulses.In principle, this was a return to the simple, robust technique used by the telegraph. Sending recognisable speech, however, meant that networks would have to carry millions of pulses a second, requiring a high (analogue) bandwidth of the transmission or storage system. Though Reeves' patent of 1937 showed how this might be done in theory, the valve-based technology of the time was not up to the job. Pulse Code Modulation would not be implemented economically until the invention of the transistor decades later. But economy was not always a priority. PCM was first used by Bell Labs for the complex and cumbersome radio system known as SIGSALY, on which Churchill and Roosevelt talked in total secrecy for much of World War 2.
PCM was a very early invention in the history of electronics, only a few years after Edwin Armstrong had invented wideband FM, a method of high-quality radio broadcasting. Noise immunity and fidelity benefit because the sound signal is no longer stored as a delicate analogue signal but as a much more robust sequence of binary numbers. Because PCM is a method of representing an analogue signal in digital form, it is particularly well adapted to work directly with digital data-processing equipment.
In his 1937 patent, Reeves formulated the major advantages of digital PCM transmission, namely
- Quality depends only on conversion steps
- Quality independent of transmission media
- Compatibility with different media and traffic (video, audio, and data)
- Low cost
- New features can easily be embedded.
Work on radio navigation
Reeves escaped just in time when the Germans invaded France - reaching England on a coal boat but losing most of his possessions on the way. He soon entered the world of Scientific Intelligence, joining the team led by Robert Watson-Watt and A P Rowe that was secretly developing radar.Although a committed pacifist, Reeve accepted the need to defeat Hitler - a task to which he contributed decisively. For in 1941, Britain faced a crisis. German bombs had reduced cities to rubble. But the invaders had been repelled and the RAF launched its own night bombing campaign against the factories that made the enemy's weapons and raw materials.
It was a disaster: British airmen had neither the experience or equipment to navigate 'blind' and bombs fell miles from their target. Defeat looked certain.
Asked to address the night navigation problem, Reeves proposed a novel solution. A pilot would reach his target by flying in an arc centred a base station, called the 'Cat', and drop his bombs when he reached a precise distance from a second station - the 'Mouse'. An audible tone told him if he was deviating from the correct track and when someone said it sounded like an Oboe, the name stuck.
OBOE was so precise that a bomb dropped from 30,000 feet could land within 50 yards of its target. In March 1943, OBOE-guided planes destroyed the mighty Krupps Works at Essen which made most of Hitler's steel and guns. On the eve of D-Day, OBOE destroyed nine of ten heavy guns that could have decimated the invading force. The RAF used OBOE in over 9,000 raids. Reeves' invention - the world's first remote-controlled bombing device - had altered the course, and perhaps the outcome, of the World War 2. Nothing as accurate as this would exist until the days of the satellite and the laser.
Work on communications systems
In 1945 Reeves returned to ITT, working at Standard Telecommunications Laboratories on ways to increase the capacity and reliability of communications systems. He was a pioneer of semiconductor devices and among the first to exploit the possibility of using light to carry information. When 'waveguides' - pipes carrying high-frequency signals - failed to work, Reeves thought of glass fibres. In the late 1960's, he inspired and led the team under Charles Kao and George Hockham that created the world's first practical optical fibre system.Alec Reeves was a visionary who in the 1950s predicted that by the end of the 20th Century people would work from home, linked by optical fibre and receiving information over a screen.
But he had a less conventional side. He was deeply interested in the capacity and character of the human brain and, like earlier scientists such as Oliver Lodge (who demonstrated 'wireless' communication before Marconi) and J.J. Thomson (who discovered the electron), Reeves explored the paranormal. For most of his life, he conducted ever more complex experiments using Geiger counters, pendulums, and electronics to measure the power of thought and to 'communicate' with the dead. He believed he was guided by the great Michael Faraday, who had died in 1867.
Alec Reeves can fairly be called 'Father' of the Information Age. Pulse Code Modulation is a method of translating an analogue, audio or video, signal into a digital representation. Without PCM, there would be no digital radio or television, no mobile telephones, no CDs, or DVDs.
He was awarded over 100 patents, as well as a CBE.
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