Pub. L. 92-410, tit. I, sec. 304

“Sec. 304. (a) Except as otherwise provided in subsection (b) of this section, any officer or member who is promoted or transferred to a higher salary class shall receive basic compensation at the lowest, scheduled rate of such higher salary class which exceeds his existing scheduled rate of basic compensation by not less than one step increase of the next higher step of the salary class from which he is promoted or transferred. “(b) Any officer or member receiving additional compensation as provided in section 302 of this Act who is promoted or transferred to a higher salary class shall receive basic compensation at the lowest scheduled rate of such higher class which exceeds his existing scheduled rate of basic compensation by at least the sum of one step increase of the next higher step of the Salary class from which he is promoted or transferred and the amount of such additional compensation.”