AMCA cancelled the class licence for all the old 121.5 EPIRB/ELT/PLB on the
01/02/10 - the new spec required it to be part of a 406 unit - this has nothing directly to do with CASA or AMSA, they are all following international standards
As for distress signals - once upon a time they used smoke signals; you would probably be rescued then arrested these days for lighting a fire in the open
