Sec. 19. MULTIPLE PENSIONS. (a) The pension board may authorize a member to make a one-time irrevocable election, on a date and in a manner established by the pension board, to cease to be a member of the pension system and, for future service only, to become a member of the retirement system governed by Article 6243e.2(1), Revised Statutes, or Article 6243g-4, Revised Statutes, or a successor statute to either of those laws, if the member:

(1) was a member of the pension system as authorized under Section 16B, Chapter 358, Acts of the 48th Legislature, Regular Session, 1943 (Article 6243g, Vernon's Texas Civil Statutes);

(2) is in a position covered by another retirement system to which the city contributes; and

(3) has not begun to receive payment of benefits from the pension system.

(b) A person who does not make an election to cease membership in the pension system under Subsection (a) of this section remains a member of the pension system as authorized under this Act.

(c) A person who makes an election to cease membership in the pension system is considered to have separated from service on the date of the election established by the pension board.

(d) Notwithstanding any other provision of this Act, duplication of any pension or benefit payable from the pension system and any pension or benefit payable under another defined benefit pension plan to which the city contributes is not permitted. Any pension or benefit payable to any person under another defined benefit pension plan, based on a period of service for which credited service is given under this Act, is deducted from the total pension or benefit otherwise payable to the participant under this Act, except that the pension or benefit may not be reduced to an amount less than the amount that would have been payable if the period of service had been excluded from service.