NEIEP Machine Room Maintenance (550) Practice Test

Mechanical selectors rely on a simple, precise drive that translates the car’s position into selector movement. A steel tape or a small cable serves this purpose well because it can be wound and unwound smoothly on a drum as the elevator moves, providing a reliable, low-stretch signal to the selector to pick the correct set of contacts for the drive system. This coded element is compact and fits inside the machine room without the bulk or complexity of other methods. A rope and pulley would be bulky and less precise; gears and springs imply a different mechanical arrangement rather than a direct drive; a pneumatic line depends on a supply of compressed air and is not the typical drive for a mechanical selector. So the steel tape or small cable is the correct driving medium.