Presentation by Oliver Völckers at the IoT-Congress 11th of October 2022 in Munich
Title: Building a robust IoT System to monitor wastewater pumps with signal processing (German language, you can use automatic translation in YouTube)
Quote from report: "Oliver Völckers, BeST Berliner Sensortechnik, offered an interesting insight into the cooperation between a small engineering company and a large corporation: How can you find out whether an ICE [train] toilet has been emptied properly if you are not allowed to install a sensor in the ICE or in the pumping station and have neither a power supply nor a mains connection available? - The solution ultimately led via the connection piece with which the pipe is connected to the train." (translated)