[GreenKeys] model 14 floating head

Mon, 03 May 2004 20:55:33 -0400

   The museum staff is correct that a "walking head" TD was used to read the tape, creeping up to the very last letter punched by
the reperforator.  This was particularly handy for cross-office tape relay systems, where the paper tape was kept as an audit trail
of traffic sent over a circuit.  If something went wrong with the circuit, the tape would be pulled back to the last successfully
received message and retransmitted.

   Kleinschmidt also made large quantities of machines for automated message offices.

   That said, much of what I saw in Model 14/15 technology was associated with "torn tape" message processing.  In these offices,
each incoming (or newly originated message) was received on paper tape.  The tape was torn off so that each message was on an
individual tape, and then each message was queued up for transmission on a triple-head TD.  One of the three heads in the
triple-head TD contained a long tape loop (typically not paper; Mylar was common), punched with channel identifications and serial
numbers from 000 through 999; e.g., KBV001 KBV002 KBV003 etc.  A serial number from this tape was sent, and then the TD would switch
to the second head to send the tape containing the actual message.  After that, if another message was already queued up on the
third head, the device would go back to the first head to send the next channel ID/serial number and then to the third head to send
that message.  The operators would manually load the 2nd and 3rd heads in alternation with message tapes.

   As time passed, electromechanical systems (followed by discrete logic and then small computers) displaced the manual labor of
tearing tapes of incoming messages, sorting them according to their outgoing routes, and queuing them up for outgoing transmission.

   Much of the electromechanical technology had analogous machines on submarine telegraph circuits (bi-polar using Morse code rather
than ITA2, because machine-sent bi-polar Morse was faster and backwards compatible with previous generations of submarine telegraphy
technology).  The C&W museum of submarine telegraphy in Porth Curno (very near Lands End) in England has beautiful brass & mahogany
equipment -- set up and run as a fully-operational cable system.  If anyone on this list ever gets over to that part of England, a
day in this museum will be well-spent.

   And now I see that I've completely wandered off the subject...

-- Eric K3NA

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Larry
Sent: 2004 May 3 19:56
To: [email protected]
Subject: [GreenKeys] model 14 floating head

Hello folks,

I've just rejoined the list after a time away. This telex is a request
for information from the Brisbane QLD Telstra museum who are not on the
internet. They have recently been given a special model 14 Teletype
reperforator to play with. Thanks to rtty.com for the 14 schematics and
to Gil for the history of telegraphy document for the 14 tech info. The
museum's got the machine going. It has a 'walking head'. I don't really
know what that means, maybe it's something to do with reading the last
letter punched, perhaps someone would enlighten me. They'd like to know
how rare or popular this machine was in the scheme of things, it was
certainly not installed anywhere here. Also, who used them and how.
They surmise it was sent to OZ for evaluation purposes before the
setting up of TRESS (Teleprinter Reperforator Exchange Switching System)
in 1959. In that network, the main teleprinter used was Siemens but
Teletype 15's were used for monitoring purposes.
Thanks chaps. The gist of this message was relayed to me from the museum
via teleprinter link thru 300baud modems to my Instrument Room so it's
on topic! Thanks for reading. Rgds = Larry

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