ClassNet Terminal User Manual
13
Although the Intelligent RS-485 Adaptor is normally used at one end of
the cable, there is no reason why the adaptor cannot be installed at some
point along the cable. This method of wiring may be more convenient in
some installations. Note, however, that the cable must be terminated
only at the ends. So if an Intelligent Converter starts a network,
termination will be at the Intelligent Converter and the last ClassNet
Terminal. If the Intelligent Converter is installed elsewhere on the
network, it will not have a terminator fitted, and termination will be on
the Terminals at each end.
The ClassNet Terminal cabling
must be run from one unit to the
next, which is often called daisy-
chained cabling. In a typical
installation, one section of cable is
connected to the Intelligent RS-485
Adaptor, and this section runs to
the first ClassNet Terminal.
Another section of cable is run
from this ClassNet Terminal to the
next ClassNet Terminal, and so on,
as shown in the diagram on the
right.
Because of the low data rate used by the ClassNet Terminal, it is
acceptable to use a small number (no more than two or three) RJ-45
joiners in the network cabling. ASP can supply special RJ-45 joiners
with pins 1, 2, 7 and 8 removed – these can be used to isolate the power
supply connections if necessary.
ASP can also supply short RJ-45 to D9 adaptor cables so that you can use
the previous version of the ClassNet Terminal (which had a D9 connector
instead of RJ-45) in a network with the current model. These adaptors
can also be used if you need to install a current ClassNet Terminal into a
ClassNet network wired for the older terminals.
Cable Termination
For proper operation, the data wires of the network cable must be
terminated at each end. Both the ClassNet Terminals and the Intelligent
RS-485 Adaptor are fitted with internal terminating resistors, which are
enabled via a jumper.
Network Expansion
Provided the cabling is correctly installed and terminated, RS-485
networks allow a maximum total cable length of 1200 metres, and can
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