An overload sensor detects when the load in the car exceeds the rated load and prevents the lift from starting. EN 81-20 requires the lift to be stopped when the load exceeds the rated load by 10 percent or by 75 kilograms, whichever is greater. The condition is signalled to passengers by an audible buzzer and an indicator, and the doors are held open until enough load is removed. The sensor is usually a load cell under the car platform or a strain gauge on the rope terminations.