[GreenKeys] Model 28 Telex?

Tue Jun 24 17:40:10 EDT 2025

John,

All of the remaining 3-row Baudot TWX machines (Model 28) were migrated to
Telex (Model 32) machines when the TWX system migrated to Western Union.
The 4-row TWX machines migrated to Western Union's Telex II service which
used WU designed hardware and software and this equipment was located in
blockhouses across the USA.

73
Russ WA3FRP

73
Russ WA3FRP

On Tue, Jun 24, 2025 at 5:28 PM John, W9DDD <w9ddd at tapr.org> wrote:

> When I left the TV station in 1970, it had a TWX 28 KSR in the reception
> area.  It had a blister on the right side similar to the one in the
> picture.  The blister was more curved and integrated with the appearance of
> the standard 28 KSR console.  Inside the blister was a 101(x) modem.  I
> think it had a TT dial, maybe even card dialer, my recollection isn't that
> sharp on that part,  I was much more interested in examining the actual 28
> after hours.
>
> After TWX was sold, I doubt they did any conversion of the TWX machines,
> but just phased them out over time.  The only Telex machines I ever saw
> were model 32 machines, but I suppose there could have been a time before
> the 32/33 line was introduced where WU could have used a 28 machine?  The
> picture of the 28 posted here certainly doesn't look exactly like the one
> at the TV station.  Similar, but not the same.  And the copy holder that
> says Western Union is a pretty good indication it's not a TWX machine.
>
> On 6/24/2025 3:00 PM, paul cembura via GreenKeys wrote:
>
> This machine most likely has a Bell 101B modem that operates on the
> switched TWX network that the Bell System sold to Western Union.
>
> Paul
> mr_rtty
>
>
> On Tuesday, June 24, 2025 at 11:43:08 AM PDT, Jeff G <jeffg at junknet.net>
> <jeffg at junknet.net> wrote:
>
>
> The dial of Telexes baffled me as well which is why I had to look it up.
> Basically my take is that the loops, etc all evolved from telegraph, and
> that Telex basically took telegraph loops and added switching to them,
> hence the dial, but it wasn't POTS, in fact a completely separate signaling
> system with different phone numbers. Signaling is done via loop control,
> for example reversing polarity tells the CCU the call is connected, etc.
> This is how we get 32s to work; just flip the polarity on the loop and the
> CCU thinks its call connected and works like a normal TTY. I think TWX was
> the evolution of Telex where it was a simliar system except using modems,
> ASCII, and standard voice/POTS lines. I know there was some computer
> integration between the two as well for a bit as I had some WU materials
> mentioning that.
>
> Jeff
>
>
>
> On Tue, Jun 24, 2025 at 2:21 PM Harold Hallikainen via GreenKeys <
> greenkeys at mailman.qth.net> wrote:
>
>
>
> On Tue, June 24, 2025 11:08 am, R Russell Miller wrote:
> > Jim,
> >
> >
> > You are correct!
> >
> >
> > A Western Union Telegraph Company Telex machine interfaced with the Telex
> >  exchange in one of two ways.  The first option was a "local loop" which
> > was a 5 ms loop when the Telex machine was idle and then a 60 ma loop
> when
> > the Telex machine was in operation. The second option, sometimes called
> > long distance or polar was used when a 60 milliampere connection could
> not
> > be achieved, provided a ground return polar circuit using 35 milliamperes
> > on separate send and receive wires.
> >
> > 73
> > Russ WA3FRP
>
> Interesting! I may be confusing various message threads. Was this a
> machine with a telephone dial on it? That made me think it operated over a
> POTS voice circuit. On the above described DC circuits, was pulse dialing
> used? How?
>
> The feed of one wire against ground is interesting. So much for balanced
> lines! I suspect this caused some pulse crosstalk into other pairs in the
> cable.
>
> Back when I first started working in radio, we had a Gates RDC-10 remote
> transmitter control (
> https://bh.hallikainen.org/uploads/harold/Gatesrdc10c.pdf ). For control,
> it used various voltages and polarities on tip or ring to ground. A second
> DC pair carried the metering sample. We soon replaced this with a Moseley
> TRC-15A ( https://bh.hallikainen.org/uploads/MoseleyTrc15a.pdf ) that used
> frequency shift keying for the control. It would shift the tone frequency
> for varying lengths of time for different functions. Metering used a
> voltage controlled oscillator.
>
> At the same station, we had a model 15 wire service machine with a tone
> demodulator (Lenkurt, I think?).
>
> --
> Not sent from an iPhone.
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> The above comments or recommendations are SWAG. Use at your own risk.
>
> John, W9DDD
>
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