Furuno INMARSAT-C FELCOM 18 Operator's Manual page 16

1. INMARSAT C SYSTEM OVERVIEW
NCS common channel
NCS/LES signaling link
LES TDM channel
MES message channel
MES signaling channel
NCS/NCS signaling link
MES interface
Terrestrial network interface
Types of MES
There are three types of MES: class 1, class 2 and class 3. This FELCOM is a class
2 MES.
Class 1:
Class 2:
Class 3:
1-4
Section
The NCS has two major functions:
• Transmit information on a common channel.
• Transmit EGC messages to MESs.
The NCS/LES signaling link connects the NCS to all
LESs in its region. All EGC messages pass through
this link.
The LES TDM channel carries the circuit control sig-
nal for MES and transmits messages from LES to
MES.
The MES message channel carries messages from
MES to LES.
The MES signaling channel transmits requests, dis-
tress alerts, data reports, etc. This channel also car-
ries login and logout from MES to NCS.
This NCS/NCS signaling link connects all NCSs. This
link exchanges data among NCSs operating in differ-
ent ocean regions.
The MES consists of the Data Circuit Terminating
Equipment (DCE) and the Data Terminal Equipment
(DTE). The DCE consists of the antenna unit, and the
DTE consists of a terminal unit, a keyboard and print-
er.
The major functions of the LESs are:
• Telex store-and-forward conversion
• Handling EGC messages
• Handling distress alerts
• Data reporting and polling
• Transmits messages to LES.
• Receives messages from LES.
• The functions of class 1 plus operation as an EGC receiver when not
transmitting or receiving.
• EGC-only receiver
The function of class 1 plus simultaneous operation as an EGC-only receiv-
er.
Description