Reminiscing about old technology...
 

I had to look up what a rheostat was. :)

Ah, I could go on for hours about old-time hardware that you young folks would just dismiss as grandpa's old-time tall tales.

Relays that had moving parts, and copper sleeves around the coils to make them unlatch after a time delay.

Memory circuits made out of a long wire that is twisted at one end, and read when the twist reaches the other end.

Vacuum tube ROM's using a shadow mask read with an electron beam steered with electric fields.

Displays using electron beams swept back-and-forth with magnetic fields hitting a phosphor behind a thick glass front. Man, those things were heavy!

I was waiting for the specific Nixie tube reference!;)

Strowger Switch

6SN7

CK722

I actually knew what all of those were, except the vacuum tube ROM. Interesting stuff. Maybe someone will replicate it in Minecraft :)

Ah, I considered adding that one to my list, but I thought I'd be the *only* one to even know what they were.

At MIT in the 1970s', I helped build and maintain a switching system for our fraternity based on these. I think we had a rack of 7 trunks -- each with a linefinder, and one final 2-digit switch.

These were units being discarded after MIT had upgraded their phone system, so they were already at end-of-life. There were times I was glad we had 7 trunks; it made it a lot easier to keep at least a couple operational!

I once had a display which had that. It had the torsion delay line as its character memory, circulating those bits around and around. The CRT sweep had a vertical wiggle added, at a frequency I think 6 times the character rate.

Rather than sweep pixel by pixel, the horizontal sweep was one sweep per character line. The bits were decoded by a pair of DA converters to address the proper character in that character generator ROM tube (it wasn't called that, of course, but that's what it was). The beam was swept horizontally, with the same 6x wiggle rate applied to the vertical, sweeping it over the shadow mask. The anode current was then used to switch the main CRT's beam, replicating that mask on the screen.

I don't remember what became of that; I even had the service manuals for it. It'd be a museum piece now...

One of my favorite parts of defcon is the museum! You should check it out if you haven't.

Re: Strowger switches.

Once you heard the sound of this device, you could never forget.....

The subscriber dials '958'.

http://www.seg.co.uk/telecomm/step1.wav

Indeed. My room was next to the closet that held them. If I paid attention, I could tell you who was calling whom.