14 CFR § 25.1711

EWIS components must be labeled or otherwise identified using a consistent method that facilitates identification of the EWIS component, its function, and its design limitations, if any.

For systems for which redundancy is required, by certification rules, by operating rules, or as a result of the assessment required by § 25.1709, EWIS components associated with those systems must be specifically identified with component part number, function, and separation requirement for bundles.

The identification must be placed along the wire, cable, or wire bundle at appropriate intervals and in areas of the airplane where it is readily visible to maintenance, repair, or alteration personnel.

If an EWIS component cannot be marked physically, then other means of identification must be provided.

The identifying markings required by paragraphs (a) and (b) of this section must remain legible throughout the expected service life of the EWIS component.

The means used for identifying each EWIS component as required by this section must not have an adverse effect on the performance of that component throughout its expected service life.

Identification for EWIS modifications to the type design must be consistent with the identification scheme of the original type design.