Each person, individually or through an agent or employee, or as an agent or employee, who operates any crane, derrick, power shovel, drilling rig, hoisting equipment, or similar apparatus, any part of which is capable of operating in closer proximity to any high voltage overhead line than is permitted by this act, shall post and maintain in plain view of the operator thereof, a durable warning sign, legible at 12 feet, stating:
"Unlawful to operate this equipment within 10 feet of high voltage overhead lines unless protected from contact danger."
Each day's failure to post or maintain such signs shall constitute a separate violation.