4 The Visual Display Unit (VDU): may be a separate unit or part of
a combined communications unit.
Keyboard: the main input device for operating and controlling the
installation and for typing messages.
6 Printer: compulsory on GMDSS fittings but optional on non-GMDSS
fit, where messages are allowed to be stored in the messaging unit/on
disk.
7 Distress Button(s): - some units have two buttons which must be
pressed simultaneously to generate a distress alert. Others have a single
button covered by a protective cover.
8 Remote Alarm Panel: GMDSS equipment must have a way of
sending Distress Alerts from the navigation position. This may be
done using a remote alarm panel. If the normal operating position of
the Inmarsat-C is in a radio room or otherwise separate from the
navigating position, the remote alarm panel will be at the normal
navigating position.Local Area Network (LAN)
Where the Inmarsat-C unit is connected to more than one
computer (e.g. as part of a LAN), the computer (or communications
unitlmessaging terminal) directly connected to the Inmarsat-C terminal
must be able, for emergency purposes, to force clear any message transfer
in progress from any other computer; delete any messages in a queue;
and return the Inmarsat-C unit to the idle state.
Inmarsat-C Store and Forward communications
Inmarsat-C offers a store and forward messaging service. With a
store and forward system, messages are not forwarded to the addressee
until they have been received completely by the LES. When you send a
message from-ship to a shore addressee, therefore, the LES will not
attempt to deliver your message until you have completed the message.
Similarly - messages from-shore to your ship will be held at the LES
until the sender has completed the message - only then will the LES
attempt to deliver the message to your vessel.
The LES will only accept messages for vessels that have indicated
that they are switched-on and listening to a particular satellite. The LES
will know that you are listening to their satellite if you have sent a LOG IN
message to the NCS.
Logging-in to your chosen satellite
Before you can use your Inmarsat-C equipment for any purpose,160 THE NAUTICAL INSTITUTE