575. BOTH INTERNATIONAL & INLAND Two power-driven vessels are crossing as shown in illustration D042RR below. Vessel «A» sounds three short blasts on the whistle. What is the meaning of this signal?

Three short blasts on a whistle signal indicate a vessel is operating astern propulsion, as defined by International and Inland Navigation Rule 34(a)(iii). This signal does not indicate intentions to hold course, signal doubt, or propose crossing ahead; those are conveyed by different signals outlined in Rule 34.