Rockwell Automation 1775-MX_S4A,D17756.3.1 User Manual PLC-3 BACKUP CONC(OR.DU1 - Manual (Page 38)

Installing a Backup System
Chapter 2
2-23
Terminators
The first and last physical device of each I/O channel requires a terminator.
Use discrete terminators (cat. no. 1770-XT) for 1775-S4A, -SR scanner
modules. The 1775-S5, -SR5 scanner modules have internal terminators
that can be enabled/disabled with a switch. See Figure 2.17 and Figure 2.7.
Figure 2.17
Selecting Terminators on 1775ĆS5, ĆSR5 Scanner Modules
1 2 3 4
Switch Positions:
UP = Switch is away from board
DOWN = Switch is toward board
When DOWN, a terminator is connected on the correĆ
sponding communication channel.
Connect a terminator when the scanner is physically
the first or last device on a Data Highway, Data HighĆ
way Plus, I/O, peerĆtoĆpeer, or backup communicaĆ
tions link; otherwise, set the switch to the UP position.
ON
OFF
ON
OFF
OFF
ON
10979ĆI
Important: When using internal terminators, removing the terminal
swing arm from a module causes the communication channels to be
unterminated.
For more information about terminators and I/O channel wiring, refer to
the PLC-3 Programmable Controller Installation and Operation Manual
(publication 1775-6.7.1).