(a) The owner, agent, or employer responsible for the operation of equipment shall post and maintain in plain view of the operator on each crane, derrick, power shovel, drilling rig, hay loader, hay stacker, pile driver, or similar apparatus, any part of which is capable of vertical, lateral, or swinging motion, an approved weather-resistant warning sign legible at twelve feet (12') reading:
(b) Warning signs shall be placed:
(1) Within the equipment readily visible to operators of cranes and other equipment when at the controls of such equipment; and
(2) On the outside of equipment in such number and locations as to be readily visible to mechanics or other persons engaged in the work operations.
(c) Warning signs should not be less than five inches (5") in height and not less than seven inches (7") in width.
“WARNING — Unlawful to operate this equipment within ten feet (10') of energized overhead electrical lines.”