The apparatus consists of a powerful U shaped magnet, a pair of brass rails complete with 4mm sockets and a brass axle. A power supply unit is connected to the rails. When the axle is placed on the rails the electric circuit is completed and the axle is repelled along the rails in a direction either towards or away from the magnetic field. Reversing the current will have the opposite effect. Dimensions: 175 x 65 x 70 mm3Additionally required: U33020-230 DC Power Supply 0 - 20 V, 0 - 5A (230 V, 50/60 Hz)orU33020-115 DC Power Supply 0 - 20 V, 0 - 5A (115 V, 50/60 Hz)