The first rock saw was built in 1992. The machine slowly articulated back and forth, cutting down until a trip switch hit the rock and the machine stopped. It would also stop on overload, low rpm, and timeout.

A worm drive would shift the whole motor/blade assembly sideways a programmable number of mm. On the end of this threaded rod used to be a steel disk with 5 points, which the proximity sensor would pick up as it turned.

The embedded MCU was a 68705R3.

This still works after 20 years unprotected outdoors!

The power board.

And this is the MCU board. If your interested you can download the Assembly code here (opens in word).