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Interpretations to Part 393 — Parts and accessories necessary for safe operation
Question 1: Does a frame channel of a CMV constitute a protective ‘‘sheath or tube’’ as specified in §393.28?
Guidance: No. To be acceptable, a sheath or tube must enclose the wires throughout their circumference. In the absence of a sheath or tube, the group of wires must be protected by nonconductive tape, braid, or other covering capable of withstanding severe abrasion.
Question 2: Must all trailers be equipped with overload protective devices?
Guidance: No. Trailers do not need overload protective devices when protection of trailer circuits is provided on the towing vehicle. A circuit breaker should be used only when the head lamp circuit is protected in common with one or more other circuits. A circuit breaker, if used, should be an automatic reset type.