[GreenKeys] Replying to David

[NNN7DXB at aol.com]

Hi Sheldon:

The ZCZC and NNNN discussion of which I spoke earlier was in fact
quite different from your take.

Mine was for a (strictly) tape relay operation - no typing online and NO
keyboards on tape relay equipment. In a tape relay, all you had were
rows and rows of tape machines spitting and sending tape (no page copies).
(As we used to say in the military tape relays: you "pulled" and "pushed"
tape (pulled = received; pushed = sent). Often you were waist deep in the
stuff. The noise and the heat from the machines was overwhelming at
times, and the smell of hot oil was everywhere.

The initial idea probably had to do with the fact that the AN/TGC-1s
used chadless tape in the early 1940s. The concept of "tape relay" was
brand new, and tape apes were, for the most part, inexperienced. The
concept of mass volume teletype traffic in tape form was new and it
was evolving.

The ZCZC and NNNN were simply visual flags to let tape handlers (tape apes)
know where one message ended and another (a new one) began in 
the tape stream, since all tapes would otherwise come in one after another,
usually without a pause,  "stop", QSL or other manual intervention between
messages. There was no automation in those days, and few, if any,
automatic machine functions.

Western Union had the contracts for the Army and Navy in those years
and that is the system they came up with. 

The WU/military system proved highly reliable and was carried forward
into the AUTODIN years where computer equipment at AUTODIN Switching
Centers was programmed to (also) look for the ZCZC (VZCZC) and NNNN
functions. These later became known as Start of Message (SOM) indicators
and End of Message (EOM) indicators. (WU also had the AUTODIN contracts
and was the principle contractor in most WW II and later fixed-station
communications installations).

Cheers,

Dave