[GreenKeys] Model 14 Typing Reperforator

[Jim Haynes]

I can't say with authority why Teletype made them both ways - of
course as you note the chadless style provides a surface to type on,
and also avoids the chad collection problem.  After that notable
election fiasco we could say that chadless tape is all hanging chads.

You probably know that in M35 there were some typing perfs and reperfs
that typed between the feed holes.

I don't know if there was a problem with reading chadless tape -
certainly there would be with something like a photo reader, but
Teletype didn't use those.  Maybe another consideration is that
fully perforated tape will spool up tighter than chadless, so you
have to empty the used-tape reel less often.

Note that the Teletype typing reperfs type 6 characters away from
the holes representing the character.  The Kleinschmidt design
that types on the edge can type the character right in line with
the holes.  Western Union also had some printer-perforators that
typed on the edge of wide tape.

Someone at Teletype did some unsuccessful experiments with a reusable
tape - made of mylar and pre-punched like chadless tape with all holes
punched.  Then the "punch" would just push the lids up, and after going
through the reader they would be pushed back down again.  But after a
few passes they either break off or fail to stay down, so you get
errors.

There are lots of strange patents for reusable or cyclic storage
devices.  Such as a loop of metal tape with holes punched and hinged
lids that can be swung to cover the holes, pushed aside to open them,
read by a more or less ordinary reader, and then reset to the closed
position.  There are a number of designs based on strings of balls
of different sizes.  And there was one in the form of a wheel or drum
having columns of 5 pins that could be pushed inward or outward.
A writing station pushed the pins and a separate reading arm sensed
them and could rotate around the drum independent of the writing
station.  Western Union actually used those devices.  When using a
multiplex system they allowed the keyboard operator or a start-stop
line to write to the drum at random speed and the multiplex to read
from it at the synchronous speed required (and of course to put in
blanks if reading caught up to the writing).

At some early RTTY gatherings (and I don't know if this was a practice
adopted from the wire telegraph business) someone would be "honored"
by being presented with an award consisting of a thimbleful of chads.

Teletype's high-speed product line always fully perforated the tape,
since there was no typing reperforator working at that speed.  My
former boss told me about a high speed tape-to-tape project they
were working on, and were having trouble with excessive errors in
testing.  They worked very hard and were in danger of missing the
product deadline but couldn't find the cause of the errors.
Eventually someone discovered that the chads were falling into a
painted metal chad container, and were picking up an electrostatic
charge in the process.  When the charge got high enough there would
be a tiny arc through the paint to the framework and the electronics
would make an error.  So the solution was to remove the paint and
make a positive ground connection between the chad bucket and the
frame.  No more errors.




jhhaynes at earthlink dot net