Ohio Rev. Code § 1567.71: Two-way communication facilities.

(A) An operator conducting longwall mining shall provide two-way communication facilities, approved by the chief of the division of mineral resources management, at the headgate and tailgate and across each longwall working face that, during the production of coal, are a separate system from the mine communication facilities. Longwall working section communication facilities shall be located at points not more than one hundred feet apart across the longwall working face.

(B) An operator conducting longwall mining shall also provide two-way communication facilities on each longwall working section. During production of coal, a designated person shall, as part of that person's other assigned duties, be available with the longwall working section communication and longwall working face communication facilities.