Special meetings of the Board of Supervisors may be called at any time by the Chair or shall be called by the Clerk upon written request of a majority of the members of the Board of Supervisors. Except in case of emergency, each member of the Board of Supervisors shall be given at least 24 hours' notice of any special meeting of the Board of Supervisors by notice in person, by telephone, or by written notice delivered personally, mailed, or left at such member's usual place of residence.