They didn't even use an ADC. They used 555 timers to produce a pulse. They measured the length of the pulse to determine the potentiometer position. Since there are 4 analog inputs, they typically used the 558 timer which is the quad version of the 555.

[–] BigDanishGuy@sh.itjust.works 6 points 4 days ago* (last edited 4 days ago) (1 children)

And here I thought I had it all figured out. But it does make sense. Doing it with an analog signal introduces noise and measuring pulse widths is going to be simpler.

[–] dethmetaljeff@lemmy.zip 2 points 4 days ago* (last edited 4 days ago)

I don't know what I'm going to do with this information but I'm glad it's in my brain now.