Until otherwise provided by law, the trial division, the orphans' court division and the family court division of the court of common pleas shall each be presided over by a president judge, who shall be one of the judges of such division and shall be elected for a term of five years by a majority vote of the judges of that division. He shall assist the president judge of the court of common pleas in supervising the judicial business of the court and shall be responsible to him. Subject to the foregoing, the judges of the court of common pleas shall prescribe rules defining the duties of the president judges. The president judge of the court of common pleas shall have the power to assign judges from one division to another division of the court when required to expedite the business of the court. The exercise of these supervisory and administrative powers, however, shall be subject to the supervisory and administrative powers of the Supreme Court.