Hysteresis refers to a pressure difference between two switching points, and thus defines the state of the output signal. The respective output signal changes when either the upper or lower limit value of the hysteresis is reached. Using the example of a vacuum switch: when the vacuum reaches a specified value, the signal changes to “ON”. If the vacuum drops below a defined value, the signal switches to “OFF”. Hysteresis is mainly used to control the air-saving function of ejectors.