Rockwell Automation 1786-series ControlNet Coax Media Planning and Installation Guide - Manual (Page 25)

Publication CNET-IN002B-EN-P - June 2010 25
Plan a ControlNet Coax Media System Chapter 2
Decide the Number of
Terminating Resistors You must use 75
Ω
terminating resistors (catalog number 1786-XT) at the end
of each segment to absorb electrical energy and prevent reflections of signals.
Terminating Resistor
After you have determined how many segments will be in your network,
multiply this number by two to figure out how many terminating resistors you
will need for your network.
Determine Repeater
Requirements 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 following graph is based on the standard ControlNet cable. If you are
using other cables, such as high-flex, this graph does not apply.
The maximum number of 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 250 m (820 ft), each segment could contain up to
47 nodes (48 connections are allowed on a 250 m (820 ft) segment - 1 tap for
the repeater).
1786-XT
1000 (3280)
750 (2460)
500 (1640)
250 (820)
2 16 32 48
S
eg
m
en
t
L
en
gt
h
m
(f
t)
Number of Taps
Repeater
Required
Repeater Not
Required
30016-m