One of the most clever things I have ever seen done with a calculator.

[pavel nemec cz]

(04-21-2020 10:00 PM)Jim Horn Wrote:  Back in the late 1970s at one of the Wescon (Western Electronics Convention and Show) events was a presentation by students competing for prizes for innovation. One presented a card reader add-on for the HP-25. Of course, I made sure to attend that! The innovation was a similar concept of having the keyboard rows and columns brought to pins of a device which would accept a classic Hollerith punched card which would be slowly pulled through by manually turning a knob which drove friction wheels to pull the card through. Each column of the card had two holes punched, one each for a row and column of the '25 keyboard which would allow those two pins to touch a conductive strip behind the punched card, thereby electrically "pressing" the corresponding key. It was as fast as the calculator and would allow loading a program into same. Of course, the resulting device was larger and more unwieldy than this one and required a keypunch machine to "program" it. But then again, it predated it by decades.

Wow, what a reminder!

I was late by half of the decade (and at that time behind the Iron curtain). In the mid 80's I did exactly the same for TI 58C. Tapping out key rows and columns to an external port. Kind of U shape loader all from PCB soldered together with spring contacts from top was very compact. I used it to load programs for concrete reinforced slabs and beams design for structural classes and exams. The challenge was punching cards since "our'' machine could do only one hole in the column and each card had to be punched in two runs and for longer programs I taped more cards together. If anybody spots the calc with this connector made by TESLA (yes, we used to have the Tesla company for all sorts of electronics - it exactly fitted on the upper slanted part of the calc enabling even use of the original case) that I lost during company move, please let me know.

KR
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