Reference designator

Common card · No. 273930

A reference designator (RefDes) unambiguously identifies the location of a component within an electrical schematic or on a printed circuit board. The reference designator usually consists of one or two letters followed by a number, e.g. C3, D1, R4, U15. The number is sometimes followed by a letter, indicating that components are grouped or matched with each other, e.g. R17A, R17B. The IEEE 315 standard contains a list of Class Designation Letters to use for electrical and electronic assemblies. For example, the letter R is a reference prefix for the resistors of an assembly, C for capacitors, K for relays. Industrial electrical installations often use reference designators according to IEC 81346 and NFPA 79 Annex E: Device and Component Designations.

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