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

[Nick England]

Here's my understanding of how the Navy did it -

TT-176B's were wired with keyboard and printer in the same loop so you
could see what you were typing and have a complete printed record of
the communication.
They were interfaced to two types of systems, TONE or CFS -
The TONE TU (mainly for UHF transceivers) would switch into transmit
automatically when you typed. The CFS system (HF) had separate rcv
converter and xmt keyer - you manually used an external rcv-xmt
switch. Shipboard, a C-1004/SG control box would have been associated
with the TT-176
http://www.navy-radio.com/rtty/c1004.htm

Hams usually had/have TU boxes hooked to a transceiver and run the
equivalent of TONE operation.

cheers,
Nick K4NYW
www.navy-radio.com

On Mon, Jul 2, 2012 at 10:59 AM, Chris Elmquist <chrise at pobox.com> wrote:
> 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
>
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