[GreenKeys] Additional Follow-Up on the use of ZCZC and NNNN

[NNN7DXB at aol.com]

All:

A few days ago, I explained the use of ZCZC and NNNN to the group
for those who might have been interested in the history of usage.

Some fine tuning of the use of ZCZC and NNNN follows for those
who are further interested.

A reference for this information is usually contained in ACP-127,
"Tape Relay Instructions", All Editions and All Supplements. ACP stands
for Allied Communications Publication and was the defacto standard
Communications Protocol Reference prior to the computer age, at
a time when teletypes were still mainstream. The ACPs prescribed
a uniform standard in which stations, CommCenters, Radio Teletype
(RATT), CW and Radio-Telephone people could communicate and
intercommunicate. Some of the most common ACPs were:

Further reference can be found in older copies of TM 11-490 and
TM-11-490-1 (Army CommCenter Manuals for Instation Procedures,
and similar other-service operating procedure publications).

Source definitions:

ACPs predated STANAGS but are of the same general vintage as JANAPs.
STANAGS are NATO standard reference publications; JANAPs are US
military Joint Army-Navy reference publications (which also include
the Air Force, Marines, Coast Guard, etc in their use). ACPs date
from the early 1950s, as do JANAPs. All of these publications, and
some newer ones, are still "on file" in most militaries today and have
never been officially phased out, even though may are no longer used.

Some ACPs of interest:

ACP-121: Communications Instructions - General
ACP-122: Communications Instructions - Security
ACP-124: Morse Code Operations
ACP-125: Radio-Telephone Operations
ACP-126: Radio-Teletype Operations (including message formats)
ACP-127: Tape Relay Instructions (including message formats)
ACP-128: NATO ALTERs Procedures
ACP-131: Operating Signals (Q and Z Series)

Many of these publications were held by NATO, and other multi-national
militaries, as well as by some non-military agencies, such as ICAO,
State Depts, MODs, WMO, Intel Agencies, ITU, etc, and while not
classified, were treated as "For Official Use Only" individually. As a
set, they were usually classified Confidential in most CommCenters.
("For Official Use Only, or FOUO, is generally "Unclassified" akin
today to more like "Unclassified But Sensitive" in that the material
is not sensitive enough to be "classified" but should be safe-
guarded and protected from general view or access by those
not requiring access).

Most of these publications are still in force today, although no longer
heavily uses since computers, for the most part, use Plain Language
rather then Prosigns, Prowords or Operating Signals (although some are
still in regular use on some circuits, such as NAVTEX from time to time).

All of these publications can now be downloaded via a Keyword
or Google search online.

"ZCZC" was always referred to as the "Start of Message" Indicator, or
"SOM". This is its' official name. "SOM" is pronounced "Some" or simply
spelled S.O.M. among communicators in most tape relays and tribs.

As stated previously, it always appeared as the first element of a
message being transmitted. It may or may not have been accompanied
by a Channel Sequence Number which generally FOLLOWED the SOM.
EX: ZCZCFMA001

When no Channel Number was used, as with many commercial stations,
the SOM appeared by itself as the start of a message: Ex: ZCZC, LF
and then text following.

NNNN is most recognized by nearly everyone as the formal end of a
teletype message, whether in tape or page copy form. As such, it
was usually referred to as the "End of Message" or "EOM" function.

In most applications, both civil and military, the 4 NNNN were preceded
by 2 CR, 8 LFs and followed by at least 12 letters keys (delete key in 
ASCII).
Military AIT schools taught that 12 LTRS keys were required after the
NNNN, but most folks used a whole string of them (more than 12).

More than the ZCZC, this told tape relay operators where to tear the
tape off of the receiving machine, as it was readily visible and
appeared in an easily readable sequence: (approximation below)...

<<   2CR
.     LF
.     LF
.     LF
.     LF
.     LF
.     LF
.     LF
.     LF
  ..  N
  ..  N
  ..  N
  ..  N
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS
.....      LTRS


Hope this tidbit clarifies it somewhat a bit more.....

Dave F
CommCenter-1