[GreenKeys] AN/FGC-38 Torn-Tape Relay Equipment

[Duncan Brown]

Paul,

You said " a real challenge to get from the receiver to another 
transmitter without a snarl-up"
When a message came in, it would be torn off of the reperforator (hence 
the term "torn tape relay") and walked (or tossed) to a tape reader bank 
for re-transmission.

Although I did hear of a story of a tape relay center where a high 
priority message came in that had to be relayed to multiple addressees 
immediately. So the tape came out of the reperforator and was fed 
directly into a tape reader and then, sequentially into other tape 
readers. But that was not the norm.


Your "running out of tape in the middle of a message " question is a 
good one, that I never thought about before.  I never worked in a big 
tape relay center, but helped build & test a transportable one for the 
Army.  I think the answer is that there would be a bank of reperforators 
and when one started showing the end of tape, it would be switched 
off-line and another would be switched/patched into that circuit.

A roll of tape would last about 5 hours at 60 wpm and about 3 hours at 
100wpm.


On the ALL CAPS of the early machines - the generic name for your M15 
(and earlier units) was a "printing telegraph" (Teletype Corp used this 
term up into the mid 1950s).  The main user of the early TTYs was 
Western Union & other telegraph companies and they started replacing 
their telegraph circuits with TTYs. But a message might travel through 
both Morse and TTY circuits. The Morse telegraph code did not have lower 
case letters, so there was no need for the printing telegraphs to have 
them, either.


AT&T bought the Teletype Corp in 1930 to have machines to lease out for 
their new TWX (TeletypWriter eXchange) service. (In Europe, it was known 
as TELEX.) This service allowed TTY users to communicate with anyone 
else on the AT&T TWX network, just like the telephone exchange service.  
Tell your daughter that your M15 is the _original_ e-mail device!

Have fun,

Duncan Brown, K2OEQ
USASA  31J30

Antique Wireless Association Museum Asst. Curator, Commercial Equipment
(also Chief TTY operator & repairman)
http://www.antiquewireless.org/

On 28-Aug-17 02:39, Paul Birkel wrote:
>
> Thanks Dave.  More great info!  A “couple of hundred feet” would seem 
> to be a real challenge to get from the receiver to another transmitter 
> without a snarl-up.  What’s to preclude “over-running” the pink 
> tape-end-coming-soon indicator and having a tape run-out before a 
> message completes?  Just monitor the receipt, accept that sometimes 
> this will happen (like various categories of receiver mechanical 
> problems) and ask for a retransmit should that happen?  Did the 
> sectioning policy manage to avoid this, by keeping the tape-length for 
> a section less than the pink-length?  Under heavy traffic conditions 
> how long would a tape-roll last and how did you manage to avoid 
> running out of tape mid-message?
>
> (And, alas, I was never able to get my Morse Code proficiency up to 
> the point of passing a radio license exam as a kid.  Now it’s all 
> “ancient history” …)
>
> One aspect of all of this has been the realization (understanding) of 
> why USMTF looks the way it does, SCREAMING CAPS :->.  I grew up with a 
> 33ASR (and minicomputers) in the 70’s and simply didn’t know of the 
> earlier Baudot era.  Store-n-forward packet-switching was the 
> new-thing for computer-communications then.  Its heritage from an 
> earlier technology was either unreported, or I simply missed it in my 
> education.
>
> This whole earlier era is an eye-opener for me.  I’m pleased to report 
> that I’ve recently become the proud recipient of an M15 and table that 
> was passed along from another list member, so it’s no longer “just 
> academic” :->.  I’ve not yet gotten to the point of putting it into 
> service, but it’s an absolutely amazing piece of equipment to examine 
> close up.  Had a bit of show-n-tell with my adult daughter last 
> month.  Even as a “still life”.
>
> Thank heaven for Greenkeys!
>
>


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