I remember a similar Mike Cook "Beeb Body-Building" article from Micro User. He used a similar layout and two potentiometers to build a "radius-arm digitiser".

I remember a similar Mike Cook "Beeb Body-Building" article from Micro User. He used a similar layout and two potentiometers to build a "radius-arm digitiser". A little bit of calibration and some trigonometry and you can work backwards from the pot positions to Cartesian X/Y co-ordinates. A little bit more work and you can enter line points from a paper drawing into the rudimentary CAD systems which existed on the BBC Micro at that time.