"Section 7.    Conversion of positions. — To permit rotation of career personnel between the Home Office and the Foreign Service, as contemplated in this Act, the positions of Counselors and the positions of chiefs of division and those of equal rank and responsibility now occupied by graduates of the Foreign Affairs Training Program in the United States Department of State are hereby converted into positions of Foreign Affairs Officers, Class I and Class II, respectively, occupying the rate in each class which the Secretary deems appropriate. The Secretary shall, by regulation, determine the manner and frequency in which Counselors, chiefs of division and occupants of positions of equal rank and responsibility shall be exchanged with Foreign Affairs Officers in the field, subject to the limitations of this Act."