The board shall hold regular monthly meetings on a date fixed by its rules, and such other meetings, after due notice to each member, as the board deems necessary. A majority of the members shall constitute a quorum, but no retirement shall be ordered, application for pension approved, warrant authorized or money paid out of the fund except upon the affirmative votes of a majority of the members taken by roll call, and entered in the official record of proceedings of the meeting at which such action is taken. All meetings shall be public.