[GreenKeys] Teletype Highspeed (>100 wpm) Equipment Question

[Sheldon Daitch]

Jim,

my very limited high speed tape reading experiences with
the Associated Press back in the late 1970s and a 35 year
old memory was that the holes had to be cut very cleanly for
the optical readers to work properly.

As I recall, the AP provided the tape punchers and the newspapers
provided the tape readers, probably something associated with the
Compugraphic photo offset printing systems used at the smaller
newspapers.

We were replacing the tape punches fairly quickly, for as the punching
pins wore, they would leave strands of the paper tape across the punched
hole.  Mechanical finger readers would go right through the stray
strands easily, but the optical readers were much more finicky.

We used the regular yellow oiled tape, and I am wondering if there was
a problem with that tape, that reducing the sensor sensitivity of the 
optical
readers, so the translucent tape would not show as a false mark, but the
stray "lint" in the punched hole was not detected as a mark.  I never got
that involved with the newspaper's equipment, they'd just keep calling us
complaining they could not read the tape, and we'd replace the punch
head and problem solved for a bit.

Sheldon


On 9/3/2012 1:10 AM, Jim Haynes wrote:
> Teletype had some experimental photo tape readers, but never produced any.
> Photo readers are capable of much higher speeds than anything Teletype
> needed.  They were popular with computers for that reason.
>
> There are problems with photo readers.  If you shine the light through
> the holes, then you have trouble reading yellow oiled tape because the
> light will shine through the tape almost as well as through the holes.
> So you see black tape used with that kind of reader.  Others depended
> on reflecting light through the holes with a mirror, which had some of
> the same problems and also could not read Mylar aluminized tape at all
> since it is mirror-shiny.  Another variety depends on diffusely reflected
> light, so Mylar reflects too well.
>
> Teletype also wanted to be able to stop the reader on a character.  That's
> hard with the really fast readers.
>
> The CX was essentially a fast version of a typical Teletype reader.
> Feeler pins that are released toward the tape by a cam and actuating
> contacts, then pulling the pins back down to advance the tape feed
> wheel.  The final reader I'm aware of, the DX, had contact wires that
> rode on the tape, making contact as they dipped into the holes.  The
> feed mechanism used as escapement.  One model, for Dataspeed Type 4,
> was reversible.
>
>
> jhhaynes at earthlink dot net
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