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

Sat Aug 26 10:16:21 EDT 2017

Pete and Group:

Tape Relay Operations were always a fascinating form of
long haul communications in the US military. Whoever came
up with it, was a genius. The amount of wiring and engineering
that went into a tape relay facility was, at times, mind boggling.
Not only was there a tape relaying capabilty, but there was also
"order wire", "cross-office", "crypto section", "technical control",
"facilities control", "teletype and crypto repair", and often times,
a separate relay "service section". Tape Relay stations were
generally large facilities. They always had an M&R (Methods
and Results) section, or an R&A Section (Reports and Analysis)
section which kept records and tabs on relay station operations.
Relays also service some of the admin needs of the tributary
stations to which they were connected. Relays were also connected
to one or more other relays.

There were three types of relays:

Primary Relays

Major Relays

Minor Relays (the illustration (photo) that was sent earlier by
navy.radio is a good example of a Minor Relay station installation.

In the Army, there were also unofficial "Terminal Relays", or trib stations
which performed relay work to lower volume stations to which they were
connected, usually within the same command, combat division, etc.

Having worked torn tape relays in the US Army over many
assignments, it was common for most relay stations to handle
over 3000 messages in a day, or over 100,000 messages in
a one month period (this information was recorded and tabulated
by the stations M&R Section who kept all the send/receive logs,
traffic counts, service messages, and all sorts of records about
everything that the relay (tape relay center) did.

100,000 messages was "small change" in later years when AUTODIN
came into being, and when military traffic volume increased expotentially
at times.

We used tape by the case, often changing tape reels several
times on the various machines during a shift. Tape relays operated
24/7, with "swing shifts" (4 to midnight or so) being the busiest.
It was common sometimes, to be knee deep in tape. Tape relays
were often very warm (hot!) too, as the machines put out a lot of heat.

Depending on the size of the relay, you could have as many as
40 or 50 people on a shift (tape relay operators were officially called
"expediters", or more commonly "tape apes".....).

Usually, in a relay, their was a SEND supervisor, and a RECEIVE
supervisor, who oversaw those operations. The whole relay was
supervised by a shift leader called a "Trick Chief" or TC. A shift
(in the Army anyway), was called a "trick"....probably a take-off
from the Western Union Labor Union definitions. I was a TC
many times....and above that, you had an OIC (Officer in Charge),
usually a Warrant Officer, or a Lieutenant or Captain (WO or
O-1, O-2, or O-3 type).

In addition to the tape relay equipment in the tape relay bay.
one could also find several ASR teletypes for Service Messages,
along with MCPU (Multiple-Call Processing Units) or ZVA
positions. Most tape relays had at least two MCPUs. I worked
them too. MCPU is when you receive a message for further
relay that has more than one stations Routing Indicator on it
(common in the military), and you have to cut a tape for each
station called. MCPUs were later replaced by AMARS (Automated
Message Addressing Routing System) which sped up the
process significantly in the relays.

The entire tape relay system was replaced more or less in the
early 1970s by AUTODIN, the Automatic Digital Network and
that lasted until Sept 30, 2003 and it too was replaced by the
DDN (Defense Data Network) which operates today as the
DMS (Defense Messaging System), sort of an email-like
architecture.

Post Note: All teletype traffic in the military was classed as
"Record Message Traffic". The tape relay systems (and later
follow ons) were the military's long-haul, worldwide messaging
system. There were several teletype networks within the
DCSTTYNET (Defense Communications System Teletypewriter
Network). 

NATO and SEATO countries also had tape relay networks,
and most of those interfaced with US networks via Gateway
Stations.

In the 1960s, all US military tape relay (and AUTODIN) operations
were integrated into a single DOD network, which also included other
US Govt agencies.

Dave
DE RUMLNHA

# # #

-----Original Message-----
From: Pete Lancashire <pete at petelancashire.com>
To: Jim Haynes <jhhaynes at earthlink.net>
Cc: Greenkeys <greenkeys at mailman.qth.net>; Nick England <navy.radio at gmail.com>
Sent: Fri, Aug 25, 2017 8:53 pm
Subject: Re: [GreenKeys] AN/FGC-38 Torn-Tape Relay Equipment

Any idea how much tape a center like the one Nick posted went though in a day ?

On Fri, Aug 25, 2017 at 5:46 PM, Jim Haynes <jhhaynes at earthlink.net> wrote:

Thanks for posting that.

There are two basic architectures for torn-tape switching.  One is represented by the AN/TGC-1 which has the reperforators and the transmitters in the same cabinet.  The other has the reperforators
in one set of cabinets and the transmitters in another, as in the
FGC-38.

An advantage of torn tape switching in general is that the routing
information is all done by humans, so it is easy to adapt to a situation
where routing is changing frequently or requires a lot of intelligence
to figure out.  The disadvantage is the need for operators to handle
all that tape manually.

The AN/TGC-1 architecture is advantageous in situations where switching
centers must be established or moved or expanded or cut down quickly.
It has the disadvantage that the routing operators get in one another's
way, and that it is extra footwork to involve a routing desk in the
process.  So the FGC-38 structure is advantageous for more fixed installations and larger installations.

It is very common in this kind of switching to have one outgoing line
fed by two tape transmitters, arranged so that only one at a time can
be sending while the other waits for the one in use to reach the end
of tape.  This allows keeping the circuit busy without the operators
having to wait for a reader to finish.  Typically there is a holder to
allow a whole bunch of tapes to be queued on a sending position.  I've
heard of situations where there were wires like clothes lines strung
across the switching room, and tapes awaiting sending humg on them with
clothes pins; but later more to-the-purpose hardware was developed.

Postal Telegraph Co. had a system in which there was a hidden reperforator
and tape transmitter associated with each outgoing line.  The idea was
to clear the switching floor transmitters quickly and let messages queue
up in the hidden reperforator.  This might have been undesirable in a
military situation where a high precedence message might pre-empt a
lower precedence message already in transmission.

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