[GreenKeys] 28 RO

[Jim Haynes]

Something used by a railroad might have a lot of stunt box stuff.  Typical
for a railroad is to have a whole bunch of stations on one line.  Then
print can be suppressed on printers that are not intended to receive a
message.  Also there may be tape readers that are polled for traffic.
And there can be more than one code to enable printing, as there may be
groups of stations that often receive the same messages.