This International Standard is applicable to the terminal markings for the main circuits of valve device stacks and assemblies, and of integrated conversion equipment. The terminal markings refer to stacks, assemblies and equipment comprising semiconductor valve devices. NOTE 1 Terminal markings for auxiliary circuits, including gate terminals and non-integrated conversion equipment with separate manufacturing of its components and their interconnection only after installation on site, are not considered in this standard. For such equipment the relevant standards, if any, for the individual components apply. Gate terminal markings are given in 6.3. Terminal markings for other circuits such as protective conductor are not considered in this standard. The object of this standard is to specify a logical alphanumeric marking system for the identification of the external main terminals of the main power circuits in a stack, valve device assembly or integrated conversion equipment, which is applicable for the purpose of reference in circuit diagrams, catalogues, descriptions, and information exchange and storage. In the case of stacks and assemblies, alphanumeric terminal marking systems are indicated for those converter connections which are the most important and most commonly used ones. Terminal marking systems making use of graphic symbols or identifying colours are not considered in this standard. NOTE 2 The terminals of auxiliary circuits should be marked such that they may be clearly identified.