Interesting Analog Technologies

We are spoiled by our cheap chips. Back in the "old days", they found creative ways to do things with analog technology.

I once saw an interesting technology for pre-RAM monitors. It was kind of an electronic Etch-A-Sketch in concept: an electron beam, roughly the same kind used in TVs, would somehow "etch" the image into the screen by displacing particles. Primitive scrolling was done by erasing the screen by some kind of global charge that put particles back on the panel (analogous to shaking the Etch-A-Sketch).

Thus, when you got to the bottom, you pressed a key that cleared the screen and continued on writing at the top. When full again, a symbol at the bottom indicated that it was ready to "scroll", awaiting your "continue" key. (Sort of a ctrl-S and ctrl-Q like behavior in DOS.)

But, it was primarily used for CAD graphics and engineering via minicomputers, not text-intensive work (probably because paper teletype terminals were still cheaper at the time for text work.) It didn't need digital RAM because the image was "stored" on the screen itself via displaced particles.

It's amazing the analog "work-arounds" they had before cheap chips. If they only found a way to put particles back on in specific spots, not just the entire screen, it could have been even more interactive.

Replace the electron beam with a grid of electrodes and you have the modern "E-ink" display. Which is locally erasable to some extent, but most e-readers will still 'flash' the screen after every few page flips to eliminate ghosting.

Then there are punched cards. But these were not "interesting" by most accounts, and generated gobs of frustration. Somewhere around here is a WarStories about punched cards going awry. I'll see if I can find it.

Punch cards were definitely an interesting technology. The data is in the holes. Burn the card, and the data's still there, but very hard to get to.

And think of all the interesting analog control circuits used for controlling motion and processes. Today, this is almost always done in software with FIR and IIR filters (generated from a software which determines the filter from a function). But an integrator (which in software needs memory) or differentiator (which is difficult to get stable for numeric data) are almost trivial in an analog circuit; just use an OP-amp, a capacitor (or inductor respectively) and a few resistors and you have got a very good integrator. The HardwareJunkies? among us can tell you much more about this. -- GunnarZarncke

I couldn't re-find it Google, but a man who helped design air-based gunning range analog computers in WWII discovered ways to make similar devices that generated psychedelic geometric patterns that most would identify as "80's style computer graphics" if shown a specimen. But he was doing it in the late 50's. It was used in the title sequence of the movie Vertigo I believe to make Spiro-Graph(TM)-like patterns, but was improved in the 60's to generate a wide variety of patterns and shapes.

If you examine the background of your U.S. currency you'll find some very intricate geometric and swirly patterns. These were originally made by a sort of Spiro-Graph on steroids called a 'rose engine lathe' http://www.flickr.com/photos/unaesthetic/1165135304/

Another thing called a "rose engine" is used to make ornamental turnings -- for example, the kind of wooden post finials you sometimes see that are carved to look like artichokes or such. This kind of machine is a sort of cam-controlled proto-CNC mill and is still used today.