Vessel A is overtaking and is the give-way vessel. Vessel B is the stand-on vessel. As the give-way vessel, A must take EARLY and SUBSTANTIAL action to keep clear of the stand-on vessel B. If both vessels are power-driven, sound signals are required. Vessel A must blow one short blast and alter course to starboardright hand side of a vessel., or blow two short blasts and alter course to portleft hand side of a vessel., and Vessel B must return the same sound signal(s) to indicate understanding.