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On 4/11/2013 3:15 PM, Tom Fine wrote: > The same expertise required to enable long distance lines of decent > audio quality was involved with driving a light valve for optical > recording and a recording stylus for electrical disk recording. Not to > mention dynamic microphones, loudspeakers and impedence-matching and > isolation transformers. And the first practical condenser mic, invented by Western Electric's E. C. Wente (who also held the patent on the dynamic mic). Bell/Western Electric also held patents on the vacuum tube amplifier (not the tube itself, but its use as an amplifier), the transistor, an early limiter circuit, L-C-R mic placement for stereo recording, and, as noted by others, the 45/45 stereo groove, independently developed by Alan Blumlein. Nyquist, who was one of several people who developed the sampling theorem that's the basis of PCM recording, was a Bell Labs engineer. Johnson, who invented Johnson noise, was too. And the list goes on. Peace, Paul