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Volumes

1. Vol 1 The Shift-Keying Family — Vol 1: Morse Was the First One Three knobs, and a machine that grabs one of them abruptly instead of smoothly. Morse code is amplitude-shift keying. RTTY is frequency-shift keying. Everything since is the same idea with more values and better arithmetic.
2. Vol 2 The Shift-Keying Family — Vol 2: Phase, Constellations, and the Tail-Eating Mode PSK31 borrowed Morse's oldest idea — short codes for common letters — and made it a bit stream. Then quadrature turned two carriers into one, and GMSK closed the loop by being an FSK and a PSK simultaneously.