22.33 Equipment for sound signals
Maritime Rules Part 22: Collision Prevention
(1) Every vessel of—
(a) 12 metres or more but less than 20 metre in length must be provided with a whistle;
(b) 20 metres or more but less than 100 metres in length must be provided with a whistle and a bell; and
(c) 100 metres or more in length must be provided with a whistle, a bell and a gong.
(2) The tone and sound of the gong must not be able to be confused with that of the bell.
(3) The whistle, bell, and gong must comply with the specifications in Appendix 3 to this rule.
(4) As long as they can still be sounded manually, the bell or the gong or both may be replaced by other equipment having the same respective sound characteristics.
(5) A vessel of less than 12 metres in length is not obliged to carry the sound signalling appliances prescribed, but if it does not carry the prescribed sound signalling appliances, it must be provided with some other means of making an efficient sound signal.