It is an overhead single track i.e. monorail or trace network on which one or more carriers ride. The carriers on this conveyor can be powered (electrically or pneumatically) or nonpowered. The carrier ranges from a simple hook to a hoist to an intelligent-vehicle like device. There can be various types in carriers like Single-carrier, single-track monorail similar to bridge or gantry crane. Multi-carrier, track network monorail is similar to both a trolley conveyor, except that the carriers operate independently and the track need not be in a closed loop, and a fixed-path automatic guided vehicle (AGV) system, except that it operates overhead. It is also termed as an Automated Electrified Monorail (AEM) system when it has similar control characteristics as an AGV system. Monorail conveyors function as materials-handling systems, similar to traveling cranes, for use in large factories. They employ a single rail run overhead with trolleys either suspended from it or run above it. Driving power is transmitted from the trolleys to the track by means of wheels that rotate horizontally, making contact with the rail between its upper and lower flanges.