All alerts come from beacons. Satellite beacon transmissions are digital, coded signals. Satellites process only coded data, other signals are rejected. Only about 1 in 5 alerts come from beacons. Satellites cannot discern beacon signals from many non-beacon sources.
Beacons transmit anonymouosly.
About 1 in 10 alerts are actual distress. Fewer than 3 in 1000 alerts and 3 in 100 composite alerts are actual distress. First alert confidence sufficient to warrant launch of SAR assets. High false alarm rate makes first-alert launch unfeasible. Absent independent distress corroboration, RCCs must wait for additional alert information.