This standard applies to all electronic equipment for control, regulation, protection, supply, etc., installed on rail vehicles and associated with: - either the accumulator battery of the vehicle; - or a low voltage power supply source with or without a direct connection to the contact system (transformer, potentiometer device, auxiliary supply); with the exception of electronic power circuits, which conform to EN 50207. This standard covers the conditions of operation, design, construction, and testing of electronic equipment, as well as basic hardware and software requirements considered necessary for competent, reliable equipment. Additional requirements in other standards or individual specifications may complement this standard, if they are justified. Specific requirements related to practices necessary to assure defined levels of functional safety are to be determined in accordance with 4.6.3.1 and 4.6.3.2 of EN 50126 and its informative Annex A. Software safety integrity level of 1 or higher shall only be considered when it is shown that a residual safety risk remains and that it has to be carried by the software driven programmable electronic system. In such a case (i.e. software safety integrity level 1 or higher), EN 50128 is applicable. For the purpose of this standard, electronic equipment is defined as equipment mainly composed of semiconductor devices and recognized associated components. These components will mainly be mounted on printed boards. NOTE Sensors (current, voltage, speed, etc.) and firing unit printed board assemblies for power electronic devices are covered by this standard. Complete firing units are covered by EN 50207.