Note 1 to entry: One or several functional units may be implemented in a single physical unit. The corresponding functional unit(s) is/are in some cases not explicitly designated.

Note 2 to entry: The various parts of a physical unit need not be functionally interrelated. For example, a physical unit may be in the form of an integrated circuit with four independent AND modules.

Note 3 to entry: If compound terms are used to designate physical units, the following, should be used as the last word (in ascending order of rank),

• component,
• assembly,
• device,
• plant.

Note 4 to entry: This entry was numbered 351-32-03 in IEC 60050-351:2006.