Starting the terminal and Log in

When you switch on the equipment, all components will be checked automatically and the terminal starts to ' log in' on the default Ocean Region. 'Log In' means, the terminal transmits via the satellite to the NCS. This transmission contains a message reporting the terminal is switched on and will be available via the satellite used . When the default satellite is not in sight, the terminal will start to scan for the strongest receiving satellite signal to “Log in”. If “Log in” has failed, the relevant ocean region must be inserted manually. After the 'log in' process the terminal will confirm that the log in procedure has been completed successfully. Normally your present NAVAREA will be kept in mind when you are deciding which satellite region you wish to log on to. The reason for choosing the satellite region will be based on your present geographical position in relation to the current NAVAREA. The EGC SafetyNET calls for a NAVAREA will be normally transmitted by only one satellite. This satellite transmitting the SafetyNET calls for your actual NAVAREA will be the one you should log on to. For more information about the SafetyNET system please consult the MSI chapter. Before switching off the Inmarsat C terminal you will need to 'log out'. Your terminal will transmit a message to the NCS telling it will be not available from that time.


Satellite Coverage Map - POR:Pacific Ocean Region, AOR-W:Atlantic Ocean West Region, AOR-E: Atlantic Ocean East Region, IOR: Indian Ocean Region.


Before you can use the Inmarsat terminal it should be commissioned. This means, the user has to fill in a commissioning form.
On this form will be written down all the details of the user, of the ship and of the equipment. Normally the 'national authority' will give the Inmarsat number at the time you get your ship station licence for the use of this equipment. The Inmarsat C number is an identification number of the terminal consisting of 9 numbers starting with the 4. Within the Inmarsat system the kind of Inmarsat terminal can be recognized by the first number used. An example of an Inmarsat C number is 424404310, where number 4 is the recognized number for Inmarsat C, 244 is MID (maritime identification digit) which is the recognized State number (in this example, 244 is Netherlands), and the last five numbers are numbers assigned to the GMDSS station. The first time the terminal logs on, a commissioning test will be performed. After this test the terminal can be used in the Inmarsat system.

The Inmarsat Enhanced Group Call (EGC) Service

The Inmarsat system is offering a service for transmission of Maritime Safety Information (MSI), namely the Enhanced Group Call service (EGC).
This EGC service, which works over the Inmarsat C system, is used to send group-call messages. This means messages sent to more than one vessel at a time.
For more explanations of the EGC consult the MSI chapter.

Position update

Normally the terminal will be connected to an external GPS, and sometimes a GPS is built into the Inmarsat C transceiver. It is vital to have an accurate position because the position in the terminal will be used when sending a distress alert. The position will also be used by the Inmarsat C terminal for the selection of received MSI messages. For more information look at the EGC part in the MSI chapter.
When there is a failure in the automatic position update you should enter the position manually. This manual position update should be done at least once every four hours.

Calculation of costs

The cost incurred by sending an Inmarsat C message will be calculated on the total number of bytes transmitted. The value of the calculation unit to be used for cost calculation is determined by LES. The charges are calculated by counting the number of packets of 256 bits that has been transmitted (per quarter of a kilo byte).
E.g. the message containing 0,75 KBit. The cost is 0,21 $/256 bits.
now you calculate the total number of bits: 0,75 x 1024 = 768 bits.
The number of packets of 256 Bits is: 768/256= 3.
The cost of the message will be 3 x 0,21 = $ 0,63.

The reception of messages is free of charge.
When someone tries to send a message to a 'logged out' terminal, the system will tell the sender the terminal is not available and no costs will be charged.
When the terminal is switched off without logging out, the LES will try to deliver the message 5 times and costs will be charged to the sender.
Last modified: Saturday, 25 April 2020, 7:50 PM