Pulse-code modulation is simply a way of representing the analog electrical signal, in digital form.

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While it's always hard to pin down the exact origins of an idea -- especially one like pulse-code modulation, where a number of parties were involved -- sifting out the large and significant contributions from the gold pan of history tends to bring up the same names time and again.

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Shannon would also contribute to the further development of pulse-code modulation (along with Bell alumni Bernard M Oliver and John R Pierce) at around the same time, using technology that eliminated some of the issues (such as complex circuitry) from the earlier, but conceptually similar, implementation from Briton Alec Reeves in 1938.

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