1. Scope 1.1 This specification covers bare combination unilay-stranded conductors made from round copper wires, either uncoated or coated with tin, lead, or lead alloy for insulated conductors for electrical purposes. These conductors shall be constructed with a central core wire surrounded by two layers of helically laid wires, resulting in an outer diameter equal to the compressed-stranded equivalent conductor. (See Explanatory Notes 1 and 2). Note 1-For the purpose of this specification, combination unilay conductor is defined as follows: a central core wire surrounded by a layer of six helically laid wires of the same diameter as the core wire with a helically laid outer layer containing six smaller wires alternated between six wires of the same diameter as the wires in the layer underneath. Both layers have a common length and direction of lay (see Fig. 1). 1.2 For the purpose of this specification, normal conductor classification (Class AA, A, B, C) is not applicable as these conductors are intended for subsequent insulation. The descriptive term combination unilay-stranded shall be used in place of conductor classification. 1.3 The SI values of density and resistivity are to be regarded as the standard. For all other properties the inch-pound values are to be regarded as standard and the SI units may be approximate.