40 ILCS 5/14-136

The Executive Secretary shall be the executive officer in charge of the administration of the detailed affairs of the system. He shall: (a) collect and receipt for all payments made to the system, including member contributions, State contributions, and other income accruing to the system, and deposit same with the State Treasurer for its account; (b) sign vouchers for the payment of moneys by the system in accordance with authorization of the board; and (c) perform such other duties as the board assigns to him.