Ohio Rev. Code § 1567.52: Additions to code of signals - posting.

The management of any mine may, with the consent of the deputy mine inspector, add to the code of signals to increase its efficiency, or to promote the safety of the workers in such mine, but whatever code is established and in use at any mine shall be approved by the division of mineral resources management, and conspicuously posted at the top, at the bottom, and in the engine room, for the information and instruction of all persons concerned.

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