The GMDSS Radio Operator must notify the NCS that the vessel will be off-line, and wait for the NCS to acknowledge with a confirmation number that must be logged.

The Inmarsat-C system can be powered down without taking additional steps once the GMDSS Radio Operator has ensured that all incoming SafetyNET™ messages have been received and stored.

The GMDSS Radio Operator may log out of the Inmarsat-C system and turn the power off (unless the vessel decides to leave the unit on during the port stay .)

The GMDSS Radio Operator must transmit an all-ships alert, to notify vessels within the satellite's footprint that the vessel will be off-line.