What is the requirement for emergency and reserve power in GMDSS radio installations?

Compulsory ships must have emergency and reserve power sources for radio communications.

An emergency power source for radio communications is not required if a vessel has proper reserve power (batteries).

A reserve power source is not required for radio communications.

Only one of the above is required if a vessel is equipped with a second 406 EPIRB as a backup means of sending a Distress alert.

What is the requirement for emergency and...