Obsolete technologies you never knew existed

[temperance]

In some countries they had wired radio:


Sublime technology.

[Bobson]

Not had, but have.

[schmitt trigger]

Unless one has seen the inside of a 1950s-era automobile radio, the vibrator power supply comes to mind.

[coppice]

TVs and radios used to be expensive. In the UK, Rediffusion https://en.wikipedia.org/wiki/Rediffusion set up shops in neighbourhoods where they received all the broadcast TV and radio channels, and used racks of amps in the shop, to drive long twisted pairs that went to the surrounding houses. They supplied simplified radios and TVs to their subscribers, which lacked any receiver section. Channel selection was a matter of selecting the right twisted pair with a switch on the radio or TV. I used to walk past one of these shops on the way to school in the 1960s. They had some big racks of electronics, with the largest vacuum tubes I have seen in a consumer application. The cost and power consumption of the equipment in the shop must have been considerable. Apparently that, and all the cabling costs, was still cheaper than having tuners in each set.

[schmitt trigger]

In the winter, these huge tubes would nicely complement wood stoves to provide warmth.
The glow emanating from the tubes would add to the cozy factor, much like a fireplace.

Warmth and a soft glow, plus music. Beautiful!

[Analog Kid]

Unless one has seen the inside of a 1950s-era automobile radio, the vibrator power supply comes to mind.

I knew about those. Those "choppers". Pretty appropriate solution for the time before solid-state electronics.

[Analog Kid]

google Clive Sinclair folded CRT and you should get some asnwers

I did that and found a few links, but what I didn't find was any diagram or picture showing how those tubes worked.
I'm still curious to know that.

I can only assume you’ve never seen one in person? It’s super obvious when you see them in operation: the phosphor isn’t on the face of the CRT, but on a flat (well, actually slightly curved) target within, and it’s at roughly 45 degrees. Watch some videos about them, it’ll be really clear.

Dave's video on this is excellent.

When I saw some pictures of another implementation of this (a Sony), it looked to me as if they were directing the electron beam at an angled phosphor target, like the first sketch here:



Which, as Dave points out, would result in a pretty unfocused image.

However, I didn't know about the "repeller" part of this scheme (bottom sketch). Very tricky how they make those electrons turn on a 90° flight path into the front-facing phosphor screen.

Very clever arrangement.

[Canis Dirus Leidy]

Optical sound recording on paper tape (Description in English by Douglas Self) from the Thirties:


P.S.The penultimate image on the link is actually the Eighties — then there was a reissue on a vinyl record.

[TimFox]

The Douglas Self website has a huge collection of archaic and obsolete technologies, along with unusual musical instruments and other hardware.

[Andy Chee]

That's interesting.
Trying to figure out how that works: the axis of the CRT is perpendicular to the screen.
Is there a mirror?
Or it looks like the phosphor surface is slightly curved perpendicular-ish to the beam.
Looks like it works pretty well. Very clever.

Adrian did a bit of experimenting with that exact aliexpress low-profile flat CRT.



I also have one in my junkbox in doorbell form.

[BrianHG]

Holy Sh-t, a portable broadcast VCR from 1967...

https://www.eevblog.com/forum/chat/holy-sh-t-a-portable-broadcast-vcr-from-1967/msg5777521/#msg5777521

[RoGeorge]

This small CRT monitor is less than 2" thick
Adrian's Digital Basement

$22?!
I want one. 


Not obsolete tech, still in use, but very unexpected when I've first found out:  The wax actuator.  Usually a piston filled with wax, and a resistor heats the wax.  When heated/cooled the wax changes its volume and moves the piston.  Pretty slow, but very strong, small and silent.

https://en.wikipedia.org/wiki/Wax_motor
https://www.aerospacemanifolds.com/thermal_actuators.html

[Haenk]

I saw a documentary on TV here in Australia about 10 years ago on the Olivetti Programma 101 programable calculator from the late 1960's. It used what they called a "magneto-strictive"  memory which was a coil of wire through which pulses were sent. The string of pulses were the bits of the memory. Kind of analogous to mercury tubes used in earlier computers like CSIRAC in Australia.

This wire was much more compact suitable for a desktop device. I found a copy of the doco on YT in Italian with some English translation. This is the point where the memory is shown.

https://youtu.be/gm_XuJS7tZY?si=dBmax645VsXzYptE&t=1012

This was the "common" type of memory used in all desktop calculators that required more than a few bits of storage, before core memories became large enough.
However they had a serious problem (by todays standards) - they were serial FIFO memories, no "RANDOM ACCESS" whatsoever.
I really suggest to read about the DIEHL COMBITRON; Wolfgang Robel made a video about it, too. That machine added another level of craziness on top. (And I have one, stored away...)

[RoGeorge]

Another funny one, the Optical Pen.  It was turning an unmodified TV screen into some sort of a "touch screen".  A pencil with a photodiode at its tip was pointing at the TV tube, while the image was flashing, half black half white, so to find out in which half of the screen the pencil is pointing.  And so on, flashing and halving the X and Y axis at each step, until the pen was fully located on the screen.  I guess epilepsy was not yet a thing back in the 80s. 

The calibration and demo start at minute 2, first part is loading the software from a cassette tape.

Dk' Tronics Lightpen for ZX Spectrum (1983) - test
Francesco Scagnelli



Another way to implement a "touch screen" for a display was to put a frame around the screen, and in the frame there were embedded IR LEDs on the X and Y axis, and they were pointing to some IR photodiodes located on the other side of the frame, in opposition with the IR LEDs.  The idea was that touching the screen with the finger will block the IR light coming from the IR LEDs on the X and Y, thus locating the position of the finger relative to the screen. 

[tom66]

I wonder if that's similar to how the LG PenTouch plasma TVs worked.  They only released this product for plasma TVs - if you embedded a hidden subfield with binary coding data into it, you could probably detect that with a synchronised photodiode.  Most plasma TVs flashed the image 600 times per second, with 10 subfields per real display frame, each subfield having differing on-times to create 10 bits of intensity control. I haven't found any detailed info on how they did this, but they never released it for LCD TVs, which suggests it's not a capacitance or resistance sensing mechanism but something related to the plasma panel itself.

https://www.trustedreviews.com/reviews/lg-pentouch-tv-first-look

[tggzzz]

The Douglas Self website has a huge collection of archaic and obsolete technologies, along with unusual musical instruments and other hardware.

http://www.douglas-self.com/MUSEUM/museum.htm

Looks like that trumps this thread!

[tggzzz]

Pneumatic logic; and, or, not, SR flip-flops, regenerator, sequencers.
https://www.parker.com/literature/Literature%20Files/pneumatic/UPD_100108/PCC-Logic.pdf

I once did a feasibility study where I recommended against replacing hydraulic logic with a microprocessor. Electricity and gas-air mixtures don't mix.

[coppice]

Another funny one, the Optical Pen.  It was turning an unmodified TV screen into some sort of a "touch screen".  A pencil with a photodiode at its tip was pointing at the TV tube, while the image was flashing, half black half white, so to find out in which half of the screen the pencil is pointing.  And so on, flashing and halving the X and Y axis at each step, until the pen was fully located on the screen.  I guess epilepsy was not yet a thing back in the 80s. 

I never saw that, but light pens to pick things from a raster scanned screen were commonplace. They usually checked the horizontal and vertical position of the scan at the moment a bright pulse was detected by the pen. Even the darkest part of the image glowed enough for the pen to detect a small pulse.

Another way to implement a "touch screen" for a display was to put a frame around the screen, and in the frame there were embedded IR LEDs on the X and Y axis, and they were pointing to some IR photodiodes located on the other side of the frame, in opposition with the IR LEDs.  The idea was that touching the screen with the finger will block the IR light coming from the IR LEDs on the X and Y, thus locating the position of the finger relative to the screen. 

That technique is still used today. It has been shrunk to a very slim plastic light pipe moulding around the edge of the display. Its commonplace with e-paper screen devices, like the Kindle. Some cars have used it (I think my Volvo works that way). Its also used for some medical applications, and other places, where people need to touch screens with gloves and very messy hands.

[tggzzz]

Another funny one, the Optical Pen.  It was turning an unmodified TV screen into some sort of a "touch screen".  A pencil with a photodiode at its tip was pointing at the TV tube, while the image was flashing, half black half white, so to find out in which half of the screen the pencil is pointing.  And so on, flashing and halving the X and Y axis at each step, until the pen was fully located on the screen.  I guess epilepsy was not yet a thing back in the 80s. 

I never saw that, but light pens to pick things from a raster scanned screen were commonplace. They usually checked the horizontal and vertical position of the scan at the moment a bright pulse was detected by the pen. Even the darkest part of the image glowed enough for the pen to detect a small pulse.

I think I still have one somewhere.

In the late 70s I thought it would be a nifty way of selecting something on the screen - long before mice were known outside Xerox PARC, of course. Never got around to it, of course.

They were definitely used in 60s military equipment with vector displays. That made it trivial to correlate the photodiode's blip with the relevant object.

They also indicated why you should never use large touchscreens for long: while mice bugger your wrists, lightpens (and similar) bugger your shoulders. (And trackballs bugger your thumbs).

[coppice]

Another funny one, the Optical Pen.  It was turning an unmodified TV screen into some sort of a "touch screen".  A pencil with a photodiode at its tip was pointing at the TV tube, while the image was flashing, half black half white, so to find out in which half of the screen the pencil is pointing.  And so on, flashing and halving the X and Y axis at each step, until the pen was fully located on the screen.  I guess epilepsy was not yet a thing back in the 80s. 

I never saw that, but light pens to pick things from a raster scanned screen were commonplace. They usually checked the horizontal and vertical position of the scan at the moment a bright pulse was detected by the pen. Even the darkest part of the image glowed enough for the pen to detect a small pulse.

I think I still have one somewhere.

In the late 70s I thought it would be a nifty way of selecting something on the screen - long before mice were known outside Xerox PARC, of course. Never got around to it, of course.

They were definitely used in 60s military equipment with vector displays. That made it trivial to correlate the photodiode's blip with the relevant object.

They also indicated why you should never use large touchscreens for long: while mice bugger your wrists, lightpens (and similar) bugger your shoulders. (And trackballs bugger your thumbs).

I question whether they were actually used in deployed military equipment, for the reason you stated. In the mid 70s we started developing a military system with a light pen, but the fatigue it caused meant we had to change that out for a trackball. A light pen can work well for occasional selection of points on a screen, but most military applications require endless selection for hours at a time. The little trackballs that went into a lot of early notebooks can make your thumb ache, but a large one sunk into the worktop, which you can spin with your palm can work pretty well. I suspect the light pens you see in movies and documentaries about the military are prototype systems.

[Kleinstein]

The optical pen type was even implemented with some home computers. I build one for the C64, using a metal can transistor with hole drilled in the top. That was all the electronics needed. Many ready made phototransistors where at bit on the slow side, but some also worked.

[iMo]

I had that (DIY) light pen for ZX Spectrum.. Rather a joke, but basically it worked.

Another technology from that time was transmitting the ZX Spectrum programs via commercial FM broadcast, or bundling programs into some computer magazines on "flexible vynil records". I tried both and it worked too..

[themadhippy]

via commercial FM

in the uk they used the tv via teletex ,but only for the bbc computers

[CatalinaWOW]

While the half interval method for finding the location of a light pen conceptually works, it is hard to believe that they actually used that.  Far simpler to just measure the timing of the pulse from the pen relative to the horizontal and vertical sync signals.  Easy to get if the pen is integrated with the display, and not that hard to synthesize even without wired connection to the monitor.  This allows position update once per frame (or twice per frame on interlaced signals if you are willing to accept 1 line of vertical error).  And no epilepsy triggers worse than standard TV.   The half interval method would require several frames to get lower positional accuracy.

[RoGeorge]

In theory, yes, but in practice it was not that easy.

The inertia of phosphorus tubes is high, tens of ms, and depends from one TV to another.  Those who were selling the home computers were usually selling them without a monitor, and the buyer was using whatever TV was heaving at home.

Then, the CPU back then was clocked at only a couple of MHz, for example the ZX Spectrum from the video was with a Z80, an 8 bit microprocessor, and clocked at only 3.5MHz.  Same processor was handling the read/writes to the video RAM, plus the execution of whatever code was running.

The total screen was 384 pixels wide, out of which 256 pixels were the useful video image, and the rest were border.  A typical TV line has 64us, out of which about 12us or so (don't recall exactly) were sync pulses.  The fastest CPU instruction was taking 4 clocks at 3.5MHz.  During this CPU instruction, the electrons spot was traveling along 8 image pixels.  Not to say, most instructions were 2-4 times longer than the minimum possible 8 pixels.

The timing was very tight, and everything was heavily optimized.  Not much room was left to detect a pencil position.  There were no dedicated hardware counter/timers yet, like there are in the nowadays microcontrollers, so all timings were to be done in software.  If exact timing was needed, you were writing each machine code mnemonic in your loop on a piece of paper, and count the total numbers of clocks needed to execute one loop.

Or else, add dedicated hardware (for example a Z80 CTC, which was another chip on the same data and address busses, very similar with the nowadays PWM/counters from MCUs).  But adding hardware extensions was expensive.