■ Inmarsat-C, Logging out when not using your MES

If you are not expecting to use your MES for a prolonged period of time, it is recommended
that you log out of your current ocean region before switching off your MES. Logging
out informs the NCS that your MES is no longer available for communication. The NCS in
your ocean region updates its database with this information. The system knows not to accept
any messages intended for your MES and informs would-be callers that your MES is not
available.

If, however, you do not log out before you switch off and a remote caller tries to send you a
message, the system will repeatedly attempt to send the message via the selected LES to your
MES. Eventually (after a number of re-tries which depend on the particular LES) the LES
will stop trying to send the message and will send a non-delivery notification (NDN) back to
the message originator. Table D-3 in Appendix D lists some of the common NDN failure
codes and their meanings.
Some MESs automatically log out when they are switched off; check with your
manufacturer’s instructions as to whether your MES has this facility. If your MES does not
have an automatic log-out facility or if you are not sure whether it does, you should always
initiate a manual log-out every time before switching off.
The message originator may also be charged by the national or international
telecommunication authorities for the time spent accessing the network (even if your MES
does not receive the message). If your MES remains switched off for a long time but still
logged in, this could prove expensive to the remote caller!