23. For the purposes of these Regulations, a person is a “qualified radar observer” if he holds:
(a)a valid Radar Observer’s Certificate granted by the Secretary of State;
or
(b)a valid certificate of attendance granted at the conclusion of a radar simulator course which has been approved by the Secretary of State;
or
(c)a valid Electronic Navigation Systems Certificate granted by the Secretary of State,
or
(d)a valid Navigation Control Certificate granted by the Secretary of State,
or
(e)a certificate recognised by the Secretary of State as being equivalent to any of the certificates mentioned in (a), (b), (c) or (d).