The speed and V-belt monitor is used to monitor rotary motion (underspeed) on motor- or belt-driven shafts. Inductive proximity switches are used to detect the speed. The pulse generation on the sensor is contactless by rotating switching cams, gears, segment discs, metal signal flags or similar. When the operating voltage is applied, the relay is activated. The monitoring function is started via the drive's power contactor at terminals E1 and E2 after the start-up bridging has expired. If the drive falls below the cut-off speed, the relay drops back. The error message of the speed and V-belt monitor is reset by resetting or switching off the operating voltage.