Rule 33 - Equipment for sound signals

A vessel of 12 meters or more in length shall be provided with a whistle and a bell and a vessel of 100 meters or more in length shall, in addition, be provided with a gong, the tone and sound of which cannot be confused with that of the bell. The whistle, bell and gong shall comply with the Rules. The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided that manual sounding of the prescribed signals shall always be possible.

A vessel of less than 12 meters in length shall not be obliged to carry the sound signaling appliances, but if she does not, she shall be provided with some other means of making an efficient sound signal.

Less than 12m - any type

12-100m - Whistle and bell

Greater than 100 - whistle, bell, and gong

Bell no longer required on vessels >= 12 but < 20