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

[Nick England]

OK, I understand 7.00 unit code means you can run a bit faster, but who
used it in practice and in what circumstances?

 I understand WU was all 7.00 - is this right?

Looking at the Navy's list of TTY units, there were both 7.00 and 7.42 unit
machines galore - how was it decided what to use where? Were all on-line
crypto machines 7.00 or some systems were 7.42 and some were 7.00? Or what?
What about Signal Corps gear?

Was there just a break and after July 17, 1958 all new Bell installations
used 7.00 or whatever? Or was this decided on a case by case basis - and
what was the basis?

Thanks for helping to reduce my confusement.
Nick England K4NYW
www.navy-radio.com
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