A Mountain Locator Unit only transmitted a signal and did not initiate a rescue (when you activated an MLU beacon, there was no one monitoring for signals, the device only assisted rescuers in locating lost climbers once a rescue has been requested by other means and rescuers know to listen and search for the beacon's signal.
A Mountain Locator Unit only transmitted a signal and did not take the initiative to rescue (when you activated an MLU beacon, there was no one monitoring for signals, the device aided rescuers in locating lost climbers after they had made a request for help and were informed of the beacon's signal).