An Australian ATSB report states a.o.:
"Records of the Australian Maritime Safety Authority’s SAR incidents shows that search and rescue personnel were alerted to aviation emergencies in a variety ways including radio calls and phone calls, and that ELT activation accounted for the first notification in only about 15 per cent of incidents. However, these ELT activations have been directly responsible for saving an average of four lives per year."
https://www.atsb.gov.au/media/412662...-128_final.pdf