12. (1) The meetings of the Board shall be held at such times and places as may be prescribed by regulations: Provided that a meeting may also be otherwise convened by the Chairman when he so thinks fit. (2) To constitute a quorum at a meeting of the Board not less than three Directors including the Chairman shall be present. (3) At a meeting of the Board each Director shall have one vote, and in the event of an equality of votes, the person presiding shall have a second or casting vote. (4) If, for any reason, the Chairman is unable to preside over a meeting, it shall be presided over by a Director nominated by the Chairman for the purpose, and in default of such nomination, by such Director as the Directors present may choose. (5) No act or proceedings of the Board shall be invalid merely on the ground of the existence of any vacancy in, or any defect in the constitution of, the Board.