How do multiple elevators decide which one is going to open its doors and let me in?


There are two elevators in my building. When they’re both at 0, and I press the “up” button, one of them opens and the other remains closed. How does it choose which one it is? Is it random? Or is it going down a list of ‘if, then’ decisions?

In: 3

> Or is it going down a list of ‘if, then’ decisions?


modern elevators have proper digital control, but automatic elevators have existed so far back that they’re among the earliest real applications of computers. outright mechanical computers that are only beat out by textile mills.

There is a controller somewhere in the building, probably in the basement, in the utility room for the elevator. That’s the computer that makes the decisions for which elevator gets sent where, which elevator answers the service call, and how to prioritize different service calls.

It’s probably not completely random, but there is a computer in the background running some soft of logical analysis to pick one. The exact details of it will depend on the settings and the computer being used.