53 Pa. Stat. § 42014
Where a city elects to create a retirement system established by this act and is then maintaining a retirement or pension system or systems covering its municipal officers and employes, those officers and employes, so covered, shall not become members of the retirement system established by this act, unless at the time the municipality elects to create the system the members of such existing pension system or systems shall, by the affirmative vote of seventy-five per centum (75%) of all the members thereof, elect to be covered by the retirement system established by this act, and the acceptance by any city of this act, by ordinance, shall constitute a repeal of any existing system or systems covering officers and employes contemplated under this act. In any such case, provision shall be made for the transfer of the moneys and securities in its pension fund or funds to the fund established by this act.
53 P.S. § 42014