So I was reading the list for the top past British innovations when I came across PCM and the Universal Machine. You have 4 days left to vote for your favourite, there really was only one choice for me in the past section. I guess you will need to wait till tomorrow to find out.

Pulse-code modulation (PCM) was invented by Alec Reeves in 1937 while developing radio telephones for transatlantic calls. He wanted to make higher-frequency radios that could carry several calls at the same time, but these conversations interfered with each other.

Reeves realised that converting these waves – analogue representations of speech – into a digital form might avoid the troublesome interference. In this way, PCM was born. He designed circuits to measure the strength of each speaker’s 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 and all that was required was a receiver that could tell the binary 1s from the 0s to turn the stream of pulses back into interference-free speech.