Why the Telephone Network Has This Shape

Telephone speech sounds like telephone speech because one band, 300 to 3400 Hz, has been held for a century. This volume traces where that band came from and then derives, one at a time, the numbers that followed from it: 8 kHz sampling, 8-bit words, the twelve bits of perceived resolution that logarithmic companding recovers, the single 64 kbit/s channel, and the 24 conversations of a T1 against the 30 of an E1. None of these came out of acoustics; each came out of what the amplifiers, the carrier systems and the exchanges of the period would allow. It closes with the list of constraints and the map that the remaining three volumes use.