Ohio Rev. Code § 301.23: County civil service commission.

The electors of any county may establish, by charter provision, a county civil service commission, personnel office, or personnel department. In any county which, by its charter, creates such a commission, office, or department, and provides a system for appointment to the county service on the basis of merit and fitness, as ascertained by competitive examination, Chapter 124. of the Revised Code is not operative; but the director of administrative services has the same powers and duties with respect to all county civil service commissions, personnel offices, and personnel departments as it possesses with reference to municipal civil service commissions.