Mental Model
Quite obviosely a thousand story elevator cannot have the button/floor mapping. It would be impossible to choose from 1000 buttons quickly, the margin of error is going to be huge, not to mention it'll be impossible to fit 1000 buttons in a standart elevator panel. This is where keypad comes to the rescue! The buttons are place the same way they are on most devices, so there is nothing new for user to learn. The function buttons are all different shapes and colors to avoid errors. There are no irreversible actions.

Just key in your floor and hit enter!