Dick: If I want to maximise my chances of being heard and assisted quickly in an emergency in Australia, I’m going to:
(1) turn on my ELT and PLB
(2) broadcast my MAYDAY on the FIA frequency.
1 will result in noises being made on 121.5 and my GPS position being sent to a friendly rescue organisation via satellite.
2 will be heard by anyone within range on the FIA including, in many cases, Centre.
Aircraft who hear either or both will tell Centre anyway. Centre will contact a friendly rescue organisation by telephone.