Privateline.com's Telephone History: Alec Reeves: Father of Pulse Code Modulation, Modern Digital Working
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ALEC REEVES 1902-1971
by David Robertson
(C) 2002 All rights reserved
Alec Reeves was one the 20th Century's
greatest, but least conventional, scientists. A brilliant engineer,
his work made the 'digital age' possible. A pacifist, he altered
the course - and perhaps the outcome - of World War II. Open-minded,
he experimented with the paranormal and believed he was in regular
contact with the 19th century inventor of electrical generation,
Reeves was born on 10 March 1902 in Redhill, Surrey. His father
Edward was Surveyor to the Royal Geographical Society. Edward
Reeves had met Livingstone, Stanley and Gordon of Khartoum -
and used his mapping skills in an effort to resolve the bitter
battle between American explorers Robert Peary and Frederick
Cook who both claimed they were the first to reach the North
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 in Reeves went to work at ITT's laboratory in Paris,
LMT. Here he worked with brilliant 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 also reported to have been seen on the roof of the LMT
building conducting paranormal experiments - though one report
said he was 'measuring moon-beams'.
It was in Paris that Reeves had the idea that made him famous
- and which helped shape the modern world. Since Alexander Graham
Bell invented the telephone in 1876, speech had been turned into
a continuously-varying wave of electric 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 networks would have to carry millions of pulses a second.
And though Reeves' extraordinary 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 could not be implement
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 on which
Churchill and Roosevelt talked in total secrecy for much of World
Reeves fled 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. A committed pacifist,
he accepted the need to defeat Hitler - a task to which he contributed
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
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. It was an amazing success.
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.
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. He
was awarded over 100 patents, as well as a CBE.
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 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 1876.
Alec Reeves - who died on 13 October 1971 - can fairly be
called 'Father' of the Information Age. Pulse Code Modulation
is the basis for all modern digital communications and media,
the main motor for change in the 21st century and perhaps the
key technology of the future. Without PCM, there would be no
Internet, no digital radio or television, no digital land-line
or mobile telephones, no CDs, DVDs or CD-ROMs. The idea of sending
information in any form, anywhere at any time would still be
the stuff of science fiction.
Editor's note: David Robertson is a science writer, television
producer, and consultant who is compiling a biography of Alec
Reeves. His e-mail is here:
For more on Alec Reeves, visit this well done web site, produced
by a one time colleague of Reeves:
Another interesting site is here. Let's hope it stays on the
[Editor's note] I've always liked the image above. It demonstrates
the differences between old and new technologies, analog and
digital, even if it shows a PCM preciseness impossible at the
time Reeves invented the technique. It's from _The Lenkurt Demodulator_,
circa early 1960s. That trade magazine took it in turn from TI.
The photo appears to be of a integrated circuit or perhaps the
top of a TI building. The text accompanying the photo says:
"Figure 3. Comparison of transmission by amplitude modulation
and pulse code modulation. Both transmissions were made under
identical conditions of noise and transmitting power. (4 db signal-to-noise
ration). Improved transmission by PCM is obtained at expense
For more on digitizing and PCM, click
here. (internal link)