CFR

86.13—Combined whistle systems.

(a) A combined whistle system is a number of whistles (sound emitting sources) operated together. For the purposes of the Rules a combined whistle system is to be regarded as a single whistle.

(b) The whistles of a combined system shall:

(1) Be located at a distance apart of not more than 100 meters,

(2) Be sounded simultaneously,

(3) Each have a fundamental frequency different from those of the others by at least 10 Hz, and

(4) Have a tonal characteristic appropriate for the length of vessel which shall be evidenced by at least two-thirds of the whistles in the combined system having fundamental frequencies falling within the limits prescribed in § 86.03, or if there are only two whistles in the combined system, by the higher fundamental frequency falling within the limits prescribed in § 86.03.

Code of Federal Regulations

Note: If due to the presence of obstructions the sound field of a single whistle or of one of the whistles referred to in § 86.11 is likely to have a zone of greatly reduced signal level, a combined whistle system should be fitted so as to overcome this reduction.

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