Applies to conductors used in industrial installations and the equipment which forms part of them, except insulated conductors constituting the terminals of electrical apparatus (e.g. rotating machines or transformers). Applies only to other installations and equipment (e.g. telecommunication circuits or circuits including telecommunication equipment) when reference is made to them. The object of this recommendation is to define the systems. Two types of markings are distinguished: main markings, supplementary markings. Purpose of marking is to provide of means whereby conductors can be identified in the circuit, ans also after they have been detached from the terminals to which they are connected.