vehicle may depend; or (c) the use of apparatus has caused or is causing undue interference with other radio communication under circumstances where all reasonable steps to minimise interference have been taken in relation to the situation or apparatus receiving such radio communication, the Commission may serve on the person in whose possession the apparatus is a notice in writing requiring that, after a date fixed by the notice, not being less than twenty-eight days from the date of the service of the notice, the apparatus shall not be used, whether by the person to whom that notice is given or otherwise, or shall only be used in such manner, at such times and in such circumstances as may be specified in the notice: (2) Notwithstanding subsection (1) (a) if, before the date fixed by the notice, a notice is given under subsection (5) requiring the Commission to refer the matter to the Appeals Board, the notice of the Commission shall not operate until the termination of the proceedings before the Appeals Board, and a notice given under this subsection by the Commission, other than a notice to which paragraph (b) applies, shall be framed accordingly; and (b) if the Commission is satisfied that the use of the apparatus in question is likely to cause undue interference with a radio communication used for the purpose of a safety of life service or for a purpose on which the safety of a person or of a vessel, aircraft or vehicle may depend the date to be fixed by the notice may be the date of the service of the notice and paragraph (a) shall not apply. (3) Subject to subsection (4), a notice under subsection (1) may be revoked or varied by a subsequent notice in writing by the Commission served on the person in whose possession the apparatus then is. (4) Notwithstanding subsection (3), where a notice under this section has the effect of imposing additional restrictions on the use of the apparatus, the provisions of subsection (2) relating to the coming into force of a notice shall apply in relation to the notice as if it had been a notice served under that subsection. (5) Where notice has been given under subsection (1), a person having possession of or an interest in the apparatus to which the notice relates may, at any time, whether before or after the date fixed by that notice, by notice in writing served on the Commission, require the Commission to refer the matter to the Appeals Board, and the Commission, unless the Commission revokes the notice given under subsection (1) or modifies the notice to the satisfaction of that person, shall refer the matter to the Appeals Board. 33