Rockwell Automation Allen-Bradley ControlNet 1786 Series, Installation Instructions Manual

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Publication CNET-IN002A-EN-P - December 2001
Plan a ControlNet Coax Media System 2-7
Determine How Many
Terminators You Need You must use 75
Ω
terminators (cat. no. 1786-XT) at the end of each
segment for the ControlNet cable system to work.
After you have determined how many segments will be in your
network, multiply this number by two to figure out how many
terminators you will need for your network.
Determine if You Need
Repeaters
You need to install repeaters if your system requires more than
48 taps per segment, or a longer trunk cable than the specifications
allow.
The maximum number of addressable nodes per link (not counting
repeaters) is 99. Since repeaters
do not require an address, they do
not count against the total of 99. If each segment is less than 250m,
each segment could contain up to 47 nodes (48 connections are
allowed on a 250m segment - 1 tap for the repeater).
EXAMPLE
If your segment requires 3 taps using 1786-RG6F/B
cable, the maximum segment length is:
([20.29 db - 3*.32 db] / 7.18 db] * 1000)
(19.33 db / 7.18 db) * 1000 = 820 m (2692 ft)
The total trunk-cable length or number of taps can
be increased by installing repeaters on the segment.
This creates another segment.
1786-XT
1000 (3280)
750 (2460)
500 (1640)
250 (820)
2
16 32 48
se
gm
en
t
le
ng
th
m
(f
t)
number of taps
Repeater
required
Repeater not
required
30016-m