______________________________________________________________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.
Paulmr_rtty
On Tuesday, June 24, 2025 at 11:43:08 AM PDT, Jeff G <jeffg@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@mailman.qth.net> wrote:
jeffg@junknet.net
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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