Ian Waugh - A Mariner\'s Guide to Marine Communications

Network Coordination Station (NCS)

The role of the NCS is to allocate a working channel to ships and

to LESs, dynamically, call-by-call. In this way, the satellite service is

used most efficiently. The NCS retains control of all working channels

on a particular satellite - no LES can hold a channel when there is no

call to be connected.

Ship Earth Stations (SES)

The communications unit onboard a ship is known as a SES - a
ship station on the earth's surface. It may also be referred to as a Mobile
Earth Station (MES). When a call is instigated from a SES, through a
particular satellite, the call request includes the LES identity through
which the ship operator wishes to place the call. The NCS allocates a
working channel and directs the SES and the LES to meet on that channel.
The LES then receives the telephone, telex, or other number required
and makes the connection. The process is automatic and is usually
completed within about 15 seconds.

Inmarsat 'to mobile' Services
To call a vessel fitted with Inmarsat equipment, whether from shore
or from another Inmarsat SES, you need to know:

• The Inmarsat ID of the ship you want to call.


• The satellite being monitored by the ship.

Every Inmarsat SES has its own unique ID, as shown below:

• Inmarsat-A 7 digits beginning with 1 (e.g. 1234567)


• Inmarsat-B 9 digits beginning with 3 (e.g. 323456789)


• Inmarsat-C 9 digits beginning with 4 (e.g. 423456789)


• Inmarsat-M 9 digits beginning with 6 (e.g. 623456789)
  Each satellite has its own telephone and telex country code. Figure
  8.1 shows the telephone/telex country codes as being:

Telephone
Telex

AORW

874

584

AORE

871

581

IOR

873

583

POR

872

582

Anyone wanting to call the above Inmarsat-A terminal, on the

IOR satellite, using normal international calling procedures from most

countries would therefore dial 00 873 1234567. The only difference in
some countries is the number of zeros required to start the international
calling sequence.

156 THE NAUTICAL INSTITUTE