Installation guide

Communications Overview
890 USE 101 00 October 2006 17
Terminating the
Cable System
A proper impedance match is maintained across the network with 75 Ω terminators.
You must install a 75 Ω terminator:
z in the unused trunk port of the last tap on the network to terminate the trunk cable
z in any open drop cable ports on taps that have been installed for future system
expansion
z in-line on cables running from the primary and standby controllers to the splitter
in a Hot Standby system; this allows you to disconnect one of the two Hot
Standby controllers while the other one maintains primary control
Terminators are present inside most drop adapters to automatically terminate each
drop connection—the exceptions are some older J890/J892 Adapters and the 410
and 3240 Motion Control products:
The devices listed above require an in-line terminator (part number 60-0513-000)
installed in the drop cable.
When a drop cable without in-line termination gets disconnected from an adapter
while the network is running, the possibility of network errors and data transfer
delays is introduced. When internally terminated adapters are installed, you may
want to consider designing mechanical self-termination into your drop cables,
particularly if a time-critical application is being run on the network. For more details
on this and other aspects of cable system termination, see Tap Connections and
Locations, p. 48.
RIO Adapters that Do Not Have Internal Termination
RIO Drop Adapters
AS-J890-001 AS-J892-001
AS-J890-002 AS-J890-002
410 Motion Controllers
110-230 110-231
110-232 110-233
3240 Motion Controllers
100-265-815
100-265-816
100-265-825
Note: The J890/J892-10x Adapters contain internal termination.
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com