[GreenKeys] 28 typer with a pretty full stunt

[Jim Haynes]

On Fri, 15 Jun 2018, Sheldon Daitch wrote:
> Jim, the question regarding the FAA, for maybe I am misreading your
> comment.  If they never had a machine off 
> sequence, eventually all the machines would be on and running.   How were
> the machines turned back off?

The FAA had two distinct roles for 28 RO machines.  One was to copy all
traffic on the circuit, such as weather reports.  The other was to copy
only traffic directed to the stations, such as flight plans.  To allow
a spare machine to be used in either role there was a solenoid mounted on
the left end of the machine that would override the selective calling and
allow everything to be printed.

In the selective calling role a machine receives a start-of-address 
sequence which allows the stuntbox to respond to call directing codes.
Receipt of a CDC puts the machine into a printing condition, or leaves
it non printing.  An end-of-address sequence causes the stuntbox to
ignore call directing codes.  And an end-of-message sequence causes
the machine to go into non-print and to respond to call directing codes.\

This may or may not be explained in the stuntbox brochure.

The FAA used nonprinting sequences for some of these functions.  I forget
which did what, but sequences like CR-CR-LTRS was one and FIGS-CR-LTRS
was another.