In addition to the rules given in IEC 60077-1, this part of IEC 60077 provides general rules for all electrotechnical components installed in power circuits, auxiliary circuits, control and indicating circuits, etc., on railwayrolling stock. The purpose of this standard is to adapt the general rules given in IEC 60077-1 to all electrotechnical components for rolling stock, in order to obtain uniformity of requirements and tests for the corresponding range of components. Electrotechnical components are mainly switchgear and controlgear, irrespective of their control, including also relays, valves, resistors, fuses, etc. The incorporation of electronic components or electronic subassemblies into electrotechnical components is now common practice. Although this standard is not applicable to electronic equipment, the presence of electronic components does not give grounds to exclude such electrotechnical components from the scope of this standard. Electronic subassemblies should comply with the relevant standard. Some of these rules may, after agreement between the user and the manufacturer, be used for electrotechnical components installed on vehicles other than railway rolling stock, such as mine locomotives, trolleybuses, etc. This standard states a) the characteristics of the components; b) the service conditions with which components have to comply; c) the tests intended to confirm compliance of the components with these characteristics under these service conditions, and the methods to be adopted for these tests; d) the information to be marked on, or given with, the apparatus. This standard does not cover industrial electrotechnical components which comply with their own product standard. In order to ensure satisfactory operation of these components for rolling stock, this standard should be used to specify only the particular requirements for railway application. In that case, a specific document should state the additional requirements with which the industrial components are to comply, e.g.: to be adapted (for example for control voltage, environmental conditions, etc.); or to be installed and used so as not to have to endure specific railway conditions; or to be additionally tested to prove that these components can satisfactorily withstand railway conditions. In the event of there being a variation of requirements between this standard and a relevant Product standard, then the product standard requirements take precedence.