Ohio Rev. Code § 1567.57: Two-way communication system.

Every operator of a mine shall install and maintain in efficient working condition a system of two-way communications approved by the chief of the division of mineral resources management connecting the surface and each landing of main shafts and slopes between the surface and each working section of any coal mine that is more than one hundred feet from a portal.

No operator of a mine shall refuse or neglect to comply with this section.