A person individually or through an agent or employee may not operate a crane, derrick, power shovel, drilling rig, hoisting equipment, or similar apparatus, any part of which is capable of vertical, lateral, or swinging motion, unless the operator or the operator's employer posts and maintains, in plain view of the operator, a durable warning sign legible at 12 feet that reads as follows: “It is unlawful to operate this equipment within 10 feet of high voltage lines.”