In the late 1970s, I was working in San Francisco for a small investment > firm . . .
Thanks for the detailed and very interesting explanation!
This flow control was achieved by sending the Model 33 a "restraint"
> which worked much like XON/XOFF flow control, but instead of sending
> an ASCII control-S/control-T, the Western Union TWX network would, I
> believe, reverse polarity of the local loop connected to the Model 33
> and the Model 33 would interpret this as a "restraint" and pause its
> transmission until the loop was returned to normal polarity.
Was this the orange light labeled REST on model 33 ASRs with the built- in modem?
It was not unusual for us to send TWX/telex documents that ran to
> dozens of pages and took well over an hour or more to transmit.
> Often, we would send these at the end of the day and leave the
> Model 33 running as it plodded along reading yards and yards of
> paper tape.
I suspect this slow speed was a reason for WU's decline. For example, in 1975 GE Timesharing offered its own ASR teleprinter that ran at 300 speed (ok, today that's slow but then it was three times as fast.)
One time we came into the office in the morning to find a plaintive
> message on the Model 33 from an overseas client requesting that we
> re-send the telex because his machine had run out of paper.
I can't help but wonder if that sort of resend happened more often, for whatever reason.
(Theoretically, this should have terminated the connection from his
> end, but it did not and we used up several hundred dollars of
> telex time sending information to his non-functioning telex machine.)
Interesting. I believe there was a level that rested on the paper roll and would trigger a low paper alarm and stop printing. But I don't know if that would merely send an x-off to stop the other machine, or actually terminate the transmission (CNTL-D EOT).
In timesharing applications, the configuration of both ends varied as did actions taken. On the dial-up ASR, EOT instantly killed the machine and shut off power. But on other machines it did nothing.
I do not recall the specific rates, but I seem to remember spending
> $500 or more to send one of these lengthy telex messages was not
> uncommon. It was expensive, but not particularly significant in the
> context of a multi-million dollar investment transaction.
> In the United States, "telecopiers" leased from Xerox and other office
> equipment manufacturers began to appear. Generally, they needed to
> be connected to a "conditioned" local loop from the phone company and
> required a similar machine from the same manufacturer on the other end.
> Federal Express feared that these machines would cut into their courier
> business and decided to invest many millions of dollars into developing
> a high-resolution private fax network linking their offices in major
> cities. One could take a document to a nearby FedEx office -- even an
> oversized document like an architectural drawing -- and have it sent to
> another FedEx location for print-out and immediate courier delivery.
> The technology was good but failed to anticipate the rapid adoption of
> low-cost private fax machines running over ordinary telephone lines.
> FedEx ended up abandoning its system and taking a write-off on its
> substantial investment.
Interesting. Western Union tried the same thing. Their facsimile service starting in the 1930s and they tried to push it big in the early 1960s, not just documents, but weather maps and related material. I have no idea of what their resolution or transmission speed was.
Thanks again for your post.
I suspect many Telex users did not have the luxury of interconnecting a new computer as you did and found the retyping of source documents and punched tape handling rather tedious, as well as expensive in manpower.
(IBM offered a punched card to Baudot paper tape converter or transmitter, but by the 1970s that was still old fashioned and of course required a mainframe to punch out cards.)
Now, WU extensively advertised advanced communications. But I don't know how much that they actually offered or at what cost or quality. I can't help but suspect that even in the 1970s WU offered mostly 110 or even slower service and only through paper tape. As mentioned, in
1960 what you describe would be considered pretty slick for an overseas transmission, but in 1975 not so much.
(I seem to recall AT&T laying a major new Atlantic cable in that era that greatly boosted overseas capacity and resulted in a significant reduction in rates. Around that time ESS and even No. 5 xbar in NYC offered IDDD. Anyone recall more?)