[GreenKeys] calibrating speed on a 14 and 15

[Jim Haynes]

There was also some procedure in an Army manual that involved sending
continuous characters and timing.  Something like the following.  The
speed should be 368 characters per minute (for 45.45 baud, 7.42 code)
which is 6.13333... characters per second.  If you adjust the margin
bell to ring at 74 characters, then hold down the space bar and it
should take right at 12 seconds from the beginning of a line for the
bell to ring.  (74 / 6.133333... is about 12)  If your keyboard is
set up for 7.00 or 7.50 code you'll have to adjust the calculation
accordingly.