[GreenKeys] Hi-speed Teletype reader...

[Jim Haynes]

In the late 1950s the military decided to standardize on power-of-two
multiples of 75 baud.  Thus the standard speeds were 75, 150, 300, 600,
1200, 2400 and up.  75 fit nicely with the Model 28 running at 100 wpm
which was 74.2 baud.  Going to 8-level, with a 100 wpm machine, the
baud rate would have been 100, except that the machines wouldn't
reliably operate with only one STOP pulse, so they had to transmit two
STOP pulses for a total of 11 bits and that required 110 baud.  Then
IBM had its Selectric terminals with something like 134.5 baud, for
reasons of their own.  Once we got away from all that mechanical stuff it
was possible to make printers running 300 baud 8-level and then 1200.
And with CRT terminals it was possible to go even faster.