[GreenKeys] series of "N"'s

[NNN7DXB at aol.com]

All:

The original ZCZC and NNNN dates from about 1942 and was the
invention or creation of Western Union for the military's then new
torn "tape relay" system. The first tape relay equipments were AN/TGC-1s
built for both the Army and the Navy.

Nearly all tape relay systems that followed from the AN/TGC-1s thru
the last AN/FGC-70s, used the ZCZC and NNNN sequences over a 
period of about 50 years. 

Since a tape relay system operates ONLY with tape, and no page
printers, it was necessary to set up a system whereby "tape apes"
(the tape relay operators) could recognize where one message
ended and another began, particularly because tape relay operations
were both prolific and unending. Tape relay stations themselves
usually consisted of rows and rows of tape transmitter (TD) banks,
tape receiving banks (reperfs), and tape monitor reel banks, usually 
arranged
in three (3) rows of equipments, depending on the size of the tape
relay station. All of the military services operated tape relay stations,
and in later years, they would number in the hundreds. Tape relays
as fixed stations finally faded into obscurity after the Vietnam War.
A few tactical (field) tape relays lasted thru the late 70s in the US Army.
(Tape relays also had other sections, such as ZVA and MCPU sections
which "split" multiple-call messages into individual tapes for their 
tribs).
 
In later years, the ZCZC and NNNN were incorporated into automatic
tape relays for the same purpose: to tell the logic circuits where one
message ended and another began.

Look closely at the tape punch holes in a tape bearing either ZCZC or
NNNN - they are unique, and are easily recognized, understood and 
memorized by tape relay operators, as their hole punches are ordered.
(In the early days, tape punching equipment did not feature printing
on the tape; you had to memorize the hole punches. In later years,
tape printing became the norm, but the ZCZC and NNNN continued
in use).

The "N" was probably a carry-over from previous use of the letter "N"
to denote the end of a CW message, and that the received message
was complete, and there were no more to follow on that particular
string of mesages (a "string" was a group of five (5) messages usually
sent in a group by a sending station).

Within a string, each message ended with the letter "B". The "B" simply 
told
the receiving operator that there was "more to follow". The "N" told the
operator that that was the "end" of the "string" of messages. Upon receipt
of the "N", the receiving operator would then send his QSL for the entire
string, or for each individual message, or as directed by the sending
station.  

On some point to point teletype circuits (1940s thru the 1960s), BBBB
was sometimes used when teletype messages were sent in a group or
"string". The last message in the string then ended with NNNN.
Much military teletype prosigns carried over from CW (Morse) practice.
Many of these same procedures were then incorporated into some
civilian and commerical applications, both foreign and domestic because
they were found to be "tried and true" and worked.

There was scuttle butt in the miltary that once suggested NNNN meant
"Nothing Follows" but there is no documentation to support this claim.
LIkewise, "BBBB" was said to indicate "More To Follow", but again,
nothing. This is all theory, but in actual practice, was quite TRUE.

Over the years, many commercial stations adoped the Western Union
practice of using both ZCZC and NNNN for the same reasons as the
military did on page printer messages. However, not all did. For 
instances, some Cuban RTTY News stations used ZKZK instead. Some
commercial stations ended their traffic with "SK" instead of NNNN.
Some German stations in the 70s ended theirs with "ENDE" ("end" in German),
while others simply used BI BI (bye bye), NNNN, or whatever suited them.
Others used the prosign "AR" (Nothing More To Follow"), or simply 
signed off with "QRU". Some weather stations ended their traffic
with the phrase "More to Follow". Many WMOGTS stations began
their weather traffic with ZCZC. The USCG still uses ZCZC on most
NAVTEX transmissions today on MF (SITOR B).

In military use, and during the AUTODIN era, the ZCZC would be changed
slightely to VZCZC. This was necessary to insure that the AUTODIN
computers did not interpret the "Z" as in ZCZC as a "Flash" (Z) message,
which was a high precedence indicator. 

Ex: VZCZCHNA123

In some applications, especially on older point to point circuits, "V"
had been used to simply start up a machine that had been turned off
remotely by a sending station at the end of its' transmission. The "V"
(a) turned on the machine, and (b) insured that the first characters to 
follow
were not lost. (Sometimes, a simple LTRS (Letters) key did the trick too,
as did hitting the "BREAK" button on the sending teletype).

Side note: Some teletype machines would shut off automatically after
30-60 seconds of idle time (Siemens machines). Others could be shut
off remotely by the sending station by hitting the Upper Case "H" -
Kleinschmidt machines. This saved wear and tear on motors). On
some TELEX machines, the loss of dial tone after 30 seconds performed
the same function. On some RATT (RTTY) stations, the loss of an
AFSK tone would also turn a machine off after a prolonged period).
In other systems, the loss or interuption of DC Line Current performed
the same function.

In military tactical use, especially in the Army and some NATO stations,
ZCZC was set aside for automatic numbering of individual messages by
tape relay equipments. 

In tactical stations without automatic numbering equipment, ZCZC was
not used. Instead, "VV" (Victor Victor) was used, as in VV   HNA123 to
denote the next Channel Number to follow. Each message carried it's
own Channel Number for message accountability over the circuit. Channel
Numbers insured that no messages were lost; any Channel Numbers that
were missing or that were out of sequence had to be protected via 
SERVICE message (protected as in "recovered"). This was usually done
via ZFX Service which then required a "pull back"  or some other manual
intervention to recover lost message traffic over the circuit.

ZCZC and NNNN (or BBBB), etc were almost never used in the ham radio
community, and neither was tape relay, which is the SOURCE of much
of the origin of these prosigns. Within this group, tape relay appears
to be not well understood, and no tape relay equipment has been preserved.
So, in that vein, I hope this fills in some of the blanks and clears up
some of the confusion as to the beginings of some of these teletype 
indicators and their procedures.

Regards to all,

Dave
CommCenter-1
Tape Ape from a bygone era