71 Pa. Stat. § 779.7
The provisions of this section shall be applicable to officers of political subdivisions not included in section 6. Such officers, subject to such regulations as the executive head of the political subdivision may issue, shall, upon approval of this act, designate by title (if feasible) or by named person, emergency interim successors and specify their order of succession. The officer shall review and revise, as necessary, designations made pursuant to this act to insure their current status. The officer will designate a sufficient number of persons so that there will be not less than three deputies or emergency interim successors, or any combination thereof. In the event that any officer of any political subdivision (or his deputy provided for pursuant to law) is unavailable, the powers of the office shall be exercised and duties shall be discharged by his designated emergency interim successors in the order specified. The emergency interim successors, in the order specified, shall exercise the powers and discharge the duties of the office to which designated until such time as a vacancy which may exist shall be filled in accordance with the Constitution or statutes, or until the officer (or his deputy or a preceding emergency interim successor) again becomes available to exercise the powers and discharge the duties of his office.
71 P.S. § 779.7