[GreenKeys] Why and When 7.00 vs. 7.42 unit code?

[Jim Haynes]

On Mon, 10 Mar 2014, Duncan Brown wrote:
> Nick - I think it was mainly the trade off between throughput and 
> maintenance.  On busy circuits, the higher speed was used, but more 
> maintenance was required and machines would not last as long.
>
And during WW-II they operated some Model 15s at 100 wpm, figuring the
traffic capacity was worth the extra maintenance and wear in the wartime
emergency.

About 1956 I saw a Model 15 operating at 100 wpm in an F.A.A. experimental
facility.  It was not a pretty sight; and they decided to get to 100 wpm
by upgrading to Model 28 machines.