[GreenKeys] Re: Ancient Technology

[jhaynes@alumni.uark.edu]

Thanks to Ben for that fine treatise on ancient technology.  I'll add a
few things that come to mind.  There is something in the phone business,
believe it is called a "pen register", that is used to record the phone
numbers that someone dials.  Mostly used for law-enforcement 
investigations, where the cops want to track who is being called by
someone they are watching.  I believe this takes almost the same kind
of court order as one for wiretapping.

Landline Morse telegraphers ceased to use the pen recorder as soon as they 
were able to convince their bosses that they could indeed copy by ear from 
the clicks the machine made.  Recorders continued to be used at some
stations, where the operator had other duties and was not always available
to copy code by ear.

Ink recorders were used on trans-Atlantic cables.  The cable code is like
Morse code except it is tri-state: one polarity for dot, the opposite for
dash, and no current for the spaces.  The cables were worked above the
Nyquist rate; that is, signals were sent so fast that the current in the
cable did not reach full strength when a single dot was sent.  It was up
to the operators to look at the wiggles on the tape and figure out what
had been sent.  There are some samples of this in the Western Union
Technical Review and other publications.

Then with radio in the 1930s and 40s there was very high speed Morse
telegraphy: 500 or 1000 wpm.  This was transmitted from punched paper
tape and received on ink recorders.  Then the tape was pulled past an
operator at a typewriter who transcribed it.  Examples of this equipment 
can be seen in advertisements of the T. R. McElroy Co. in the back of
the ARRL Handbooks of the 40s and 50s.

Western Union had an ink recorder called an "undulator"   I believe this 
was used as test equipment.  You could look at signals coming from a
TTY, for example, and see if any of the transmitter contacts were bouncing 
or operating at the wrong times.

The burglar alarm system Ben described is very much like the fire alarm
systems, and also like the messenger-call system used by Western Union.
Sometimes you see the call boxes at antique dealers' - an oval shaped
porcelain base with a metal cover in white and blue enamel, and a handle
sticking out.  A later model was a yellow box.  You wind up the handle
and release it, and the spring-loaded mechanism sends out a short message
in dots and dashes.  This gets recorded at the W.U. office on a paper 
tape, where the messenger superviser reads it and sends out a messenger.
This continued in service into the 1950s at least.  Of course it would
have been a lot easier just to call W.U. on the telephone.



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jhaynes at alumni dot uark dot edu