Rockwell Automation 1786-series ControlNet Coax Media Planning and Installation Guide - Manual (Page 18)

18 Publication CNET-IN002B-EN-P - June 2010
Chapter 2 Plan a ControlNet Coax Media System
Determine the Number of
Taps You Need The number of taps you need depends on the number of nodes you want to
connect to the network. You need a tap for each node and repeater on
a segment.
If you plan to add nodes at a later date, you should order and install the cable
and taps for these additional nodes when you install the initial network. An
additional tap may be installed on a segment for maintenance purposes. The
maintenance tap may be un-terminated; all other taps must either be
connected to a node or to a tap dummy load (catalog number 1786-TCAP).
All taps installed in a segment must not exceed the maximum allowable
segment length for the number of installed taps as detailed on
page 23 .
The illustration below shows available tap kits. The IP67 T-tap includes a drop
cable that is removable from the tap body.
Available Tap Kits
IMPORTANT
A disconnected drop cable can cause noise on the network.
Because of this, a 1786-TCAP is recommended at all
unconnected drop cables. The tap dummy load matches the
impedance of an operating device to limit noise entering the
system through an unconnected tap. This component is
different from a trunk cable terminating resistor.
In addition, a disconnected trunk terminating resistor can have
unpredictable effects to the network, including the inability to
communicate due to reflections. Each segment must be
terminated with a 1786-XT unit at each end of the segment.
TIP
You may want to use a BNC bullet connector in place of a tap if
you plan to install additional nodes in the future.
The bend radius is 1.5 in. for all fixed-tap drop cables.
Straight T-tap Straight Y-tap Right-angle T- tap Right-angle Y-tap IP67 T-tap
20094-M