The designs for some of the first push button elevator circuitry was really cool tech.

It was a complicated problem because elevators could appear and disappear in a given building at will. Some would appear and operate within a building for only a few minutes. Otherwise could leave seconds after they arrived without signaling their departure. The circuitry had to account for this unreliability within the "network" of all possible elevators within a given city block.

The circuity in each elevator car also had to handle collision avoidance as new elevators appeared within the same shaft as other elevator cars that were already moving in that shaft.

It's fascinating to look at the designs:

www.archive.org/apples-and-oranges.html

Self-driving cars seem like a cake walk by comparison.