A container’s fill level can be monitored with a liquid level sensor. In principle, they are optical sensors – an LED transmitter is located in the same housing with a phototransistor receiver. If the liquid level rises to the tip of the sensor, the light emitted by the LED is reflected differently. An integrated voltage regulator then detects a change in voltage in the receiver and immediately switches the binary output signal either on or off. There are many applications, ranging from home applications to industrial uses in mechanical engineering or the chemicals industry to medical technology applications.