Furuno FELCOM 12, Service Manual

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1-8
4) SES message channel
The SESs use this channel to transfer messages to a LES. Each LES has a number of SES
message channels assigned to it by the NCS. Message transfer begins with the reception
of a logical channel assignment packet. Allocation of SES message channels to SESs is
done by the LES via the assignment packet.
5) SES signalling channel
This channel is used by the SESs to transmit signalling packets (channel assignment
request, distress call, data reporting, etc.).
Each LES have more than one SES signalling channels.
6) NCS/NCS signalling link
This is an inter-regional data connection between each of the NCSs. It functions for
NCSs to exchange information about SESs currently operational in their coverage area.
7) MES interface
The MES consists of the Data Circuit Terminating Equipment (DCE) and the Data
Terminal Equipment (DTE). In this system, the DCE consists of the antenna unit and the
communication unit. And the DTE consists of the terminal unit (or PC).
8) Terrestrial network interface
The major functions of the LESs are;
(1) Store-and-forward telex service
(2) EGC broadcasting
(3) Distress alerting and Safety services
LES channel assignment
All LES channel assignments are made by the NCS in its region; the assignments can be
permanent or demand assigned on the following channels.
(a) CES TDM channel
(b) SES signalling channel (40 CH max per CES TDM channel)
(c) SES message channel requested by LES