For a satellite to find someone who needs help, it needs to have a locator system. Current search and rescue systems carry a piece of equipment called a repeater on board their satellites. The repeater receives and retransmits signals anytime the satellite is close enough to be in contact with a ground station.
Such satellites also carry a receiver-processor and memory unit. They are designed to receive, process and store received signals. The purpose of the receiver-processor and memory unit is to demodulate the digital messages received from beacons, to measure the received frequency, and to record the time the measurement was taken.