Hmm.. Analog "Vocoder" technology was invented in 1939 https://en.wikipedia.org/wiki/Vocoder https://en.wikipedia.org/wiki/Vocoder So I'd imagine that by 1993

Hmm.. Analog "Vocoder" technology was invented in 1939 https://en.wikipedia.org/wiki/Vocoder https://en.wikipedia.org/wiki/Vocoder So I'd imagine that by 1993 it would have been possible to do analog voice coding, digitize the codes, and then a mainframe could scan through the codes which are just "envelopes of the bandpass filters". (Just a guess)