Explanation: An EPIRB, or Emergency Position-Indicating Radio Beacon, is a crucial piece of maritime safety equipment. It is a battery-operated radio transmitter designed to automatically activate and float free from a sinking vessel. Once activated, it broadcasts distress signals on specific frequencies—406 MHz for satellite detection (part of the Cospas-Sarsat system) to determine its position, and 121.5 MHz as a homing signal for search and rescue teams. This allows for rapid location of individuals in distress, significantly increasing chances of rescue. Option B describes a general warning system, not the specific function of an EPIRB, which signals *after* an emergency has occurred. Option C refers to a broader system like the Global Maritime Distress and Safety System (GMDSS), of which an EPIRB is a component, not the entire system itself. Option D is an unrelated audio device.