What type of signals are transmitted by emergency positioning-indicating radio beacons?

Emergency positioning-indicating radio beacons (EPIRBs) are designed to transmit specific signals that play a crucial role in search and rescue operations. The correct choice highlights that these signals are indeed radiocommunication signals. When activated, EPIRBs send out distress signals that contain information regarding the beacon's location, enabling search and rescue teams to pinpoint where assistance is needed.

These signals operate on internationally recognized frequencies, typically 406 MHz, ensuring that they can be detected by satellites and, in some cases, by nearby vessels. The primary purpose of these radiocommunication signals is to provide immediate assistance to distressed vessels or individuals, which aligns with their role in maritime safety.

The other options do not accurately reflect the function of EPIRBs. While emergency alerts are an aspect of the distress signals transmitted, the defining characteristic is that they are radiocommunication signals specifically aimed at facilitating rescue operations.