Digital sound was invented in 1937 鈥� decades before the technology to use it had been developed
THOUGH he didn鈥檛 realise it at the time, in 1937 the laid the foundation stone of modern digital telecommunications networks. The valve (vacuum tube) was then in its heyday, digital computers were still years in the future, and the transistor a decade away.
In 1927, commercial transatlantic telephone calls were made possible by radio telephones. In the early 1930s, Reeves helped develop higher-frequency radios that could carry several calls at the same time, but these conversations interfered with each other, producing a noisy, hard-to-understand signal.
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Then Reeves realised that converting these analogue representations of speech into a series of telegraph-like pulses might avoid the troublesome interference. He designed circuits to measure the strength of each speaker鈥檚 voice 8000 times a second and assign that signal strength to one of 32 levels. Each level was then represented by a sequence of five binary digits. As long as the receiver could tell the binary 1s from the 0s, it ought to be able to turn the stream of pulses back into interference-free speech.
That was the theory, at least. 鈥淣o tools then existed that could make it economic,鈥� he wrote more than 25 years later. His employer, ITT, patented pulse-code modulation, but never earned a penny before the patent expired in the 1950s.
Reeves was something of a visionary, often saying: 鈥淚 will be right about the things that I say are going to happen, but I will never be right about when.鈥� Perhaps he thought he really could see the future. He studied spiritualism and believed he was getting signals in Morse code from other worlds.
ITT managers eventually put him in charge of exploratory research at the Standard Telecommunications Laboratories in Harlow, Essex. In that role, he launched a group to study laser communications, and enthusiastically supported that led to the fibre-optic network that today carries pulse-code modulated light signals around the world.
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