All elevators, whether traction or hydraulic, require a machine room to store large electric motors (or hydraulic pumps) and a controller cabinet. This room is located above or below the hoistway (or only below, for hydraulic elevators) and may contain machinery for a single or a group of elevators. Modern day traction motors boasting gearless and permanent magnet drive can be more compact and efficient; electronic microprocessors have replaced the mechanical relays. As a result, traction elevators can be built without a dedicated room above the shaft, saving valuable space in building planning.