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Instruction Manual
27
E04252
4.2.1 Network Termination
The IS12 system is based around a high speed data bus net-
work. Although this is very robust, on very large or complex
systems with many instruments the system may need to be
properly terminated to ensure the integrity of the network. For
this purpose a network terminator (Fig 4.9) is supplied with
some IS12 instruments, including the IS12 Mega. The termina-
tor simply plugs into the last free network port in the daisy-
chain. The terminator only needs to be fitted under certain cir-
cumstances -
The terminator is not required if -
a) The Mega instrument is used only as an NMEA repeater
unit and is not connected to other IS12 instruments
b) There is already a terminator fitted to the system. There
should only be one terminator fitted per system.
c) The system includes an IS12 Wind Transducer. The Wind
Transducer has an inbuilt network terminator.
d) The total system cable length (excluding the power cable)
is less than 5m. A small IS12 system does not require a termina-
tor.
If the installation does not meet any of the above criteria, the
terminator should be fitted to the spare network port at the end
of the longest cable run.
A three way cable joiner (part no. SDJ) is available as a sepa-
rate accessory. Any unterminated spurs created using the SDJ
must be less than 5m in length (Fig 4.10) -
Fig 4.10 - Creating cable spurs using SDJ three way joiner
Three Way
Joiner SDJ
Spur -
max cable
length 5m
Spur -
max cable
length 5m
Terminator fitted to
end of longest spur
Fig 4.10 - Network Terminator