[GreenKeys] Police teletype

[Jim Haynes]

On Wed, 18 Dec 2019, Ralph Irish wrote:

> In 1969 and later, I had a second job at a two-way radio service and
> was doing something, but nothing was showing on the paper.  I told him about
> 'Print Suppression' and
> I opened the cover and found the Print Suppression solenoid and pointed it
> out to him.  When the 

The solenoid might more accurately be called 'Print Non-Suppression' and
was an optional add-on to a printer that had selective calling installed.
I believe they were first used by the FAA.  They had some circuits that
used selective calling for material like flight plans, where only stations
connected with a particular flight needed to copy.  They had other 
circuits like weather where stations needed to copy everything.  The
solenoid was controlled by a Local-Remote switch on the front of the
machine.  This allowed them to have a spare machine that could work
in either kind of network as needed.  The solenoid seems like a crude way
to handle the function, but maybe the customer wanted to be able to
control it remotely as well as from the front of the machine.