EN 50155 standard regulates all the details required to test the functionality of the electronics on a train. The aim of the tests is to achieve a functional capability that lasts 24 hours a day for 20 years. This covers approximately 175,000 hours. All requirements are defined that must be met under all conceivable environmental conditions. This includes shock, vibration, fog, salt and the like. In addition, the EN 50155 standard specifies how to deal with fluctuations in supply voltages and their transients.