[GreenKeys] M28 half vs full duplex? One loop or two?

[Chris Elmquist]

I'm getting close to having my M28 "skintight" TT-176B up and running
and was working on it this past weekend.

I'm not sure if this unit is the "tempest" version but it does have a
line filter assembly through which both the AC line and the loop feed
into the unit at the back of the LESU.

What's a little puzzling to me is that there is just one circuit through
the filter for the loop.  It enforces that the keyboard and the printer
must be in series and then there is just a single + and - loop connection
coming away from the unit.  This means that it will be half duplex--
it will print what is locally typed.  At least, I think that's the idea.

Was this the normal configuration of this unit?  or was it also configured
with the keyboard and the printer on separate loops?  So that you could
have a full duplex connection?

I kind of live in a cross-over space between TTYs used for wireline and
radio comms and those hooked to computers.  My Altair 680b has a monitor
PROM that can support a 5-level baudot TTY as the console.  But there,
the keyboard loop and the printer loop are separate-- very similar
to how it was often done with ASCII M33 machines.   So, I'm a little
confused/curious about the "normal" way of using a 5-level machine and
it's loop (or loops)...

Chris

-- 
Chris Elmquist