The Direction of Rotation Detector is a three terminal switch. The movable arm is connected electrically to the center terminal. A belt connected to the arm passes over a shaft driven by the motor. If the motor starts to run in a clockwise direction, the belt pulls the contact arm over until the left-hand contacts are closed. The arm is prevented from moving further, and the belt slips on the shaft, holding the contacts closed by means of friction. Counterclockwise rotation of the motor will open the left-hand contacts and close the right-hand contacts. This enables the switch to be used for detection of the direction of rotation of a motor.