Communications and Multimedia 35 (h) his performance has been unsatisfactory for a significant period of time. (2) The Chairman or any member may, at any time, resign his office by giving a written notice to the Minister. Vacation of office and acting appointments 21.  (1) The office of the Chairman or any member of the Appeal Tribunal shall be vacated if— (a) he dies; (b) he resigns or otherwise vacates his office before the expiry of the term for which he is appointed; or (c) his appointment is terminated. (2) The Minister shall appoint a person in accordance with section 17 to replace the Chairman or any other member during the vacancy in the office of the Chairman or any other member. (3) The Minister shall appoint a person in accordance with section 17 to act as the Chairman, or any other member— (a) during any period when the Chairman or any other member is absent from any duty or from Malaysia; or (b) if the Chairman or any other member is, for any reason, unable to perform the duties of the office. (4) The exercise of the powers, or the performance of the functions, of the Appeal Tribunal is not affected only because of there being a vacancy in the membership of the Tribunal. Quorum for the Appeal Tribunal 22. The quorum for the Appeal Tribunal shall be formed by— (a) a Judge; and (b) at least two other members, or any greater even number of members not exceeding four, none of whom are Judges, for the purposes of the functions of the Appeal Tribunal under this Act.