(1) Where:
(a) an employee who becomes a contributor after the commencement of the Superannuation Act 1971 was, immediately before becoming an employee, a contributor to a Public Service Superannuation Fund; and
(b) section 109 does not apply in relation to him;
the succeeding provisions of this section have effect.
(2) If at any time the number of units of pension for which the employee would, but for this section, be required to contribute to the Fund does not exceed such number of units of pension (including, where necessary, a fraction of a unit of pension) as the Board determines to have been equivalent, as at the date on which he became a contributor, to the amount refunded to him from the Public Service Superannuation Fund upon his ceasing to be a contributor to that Fund, the employee shall not be required or permitted to contribute to the Fund at that time in respect of units of pension.
(3) If at any time the number of units of pension for which the employee would, but for this section, be required to contribute to the Fund exceeds the number of units of pension that are specified in the determination made by the Board in relation to him under subsection (2), the employee shall not be required or permitted to contribute to the Fund at that time in respect of a number of units of pension greater than the excess.