30 CFR § 75.906
Trailing cables for mobile equipment, ground wires, and ground check wires.
[STATUTORY PROVISIONS]
Trailing cables for mobile equipment shall contain one or more ground
conductors having a cross-sectional area of not less than one-half the power
conductor, and, on September 30, 1970, an insulated conductor for the ground
continuity check circuit or other no less effective device approved by the
Secretary or his authorized representative to assure such continuity, except
that an extension of time, not in excess of 12 months may be permitted by the
Secretary on a mine-by-mine basis if he determines that such equipment is not
available. Splices made in the cables shall provide continuity of all
components.