Rockwell Automation 1791-XXXX Discrete I/O AC and DC Block I/O Input and Output Modules - Manual (Page 53)

Installing Block I/O
Chapter 3
3-34
A termination resistor must be installed on the last block in a series.
Connect the resistor as shown in Figure 3.23.
Figure 3.23
Installing the Termination Resistor
Termination
Resistor
Connect termination resistor across
terminals 6 (BLU) and 8 (CLR).
10835ĆI
BLU
SHD
CLR
Refer to Table 3.A for proper
terminator for your application.
Output modules contain surge suppression circuitry for the block output
devices. The ac output modules provide an RC network to limit the
magnitude of voltage transients that may occur when a device is wired in
parallel or series with hard contacts. The dc output modules have clamping
diodes that shunt voltage transients to the power supply.
Important: We recommend that you use an additional suppression device
if an output module is being used to control an inductive device such as:
relays motor starters
solenoids motors
and is in series with or parallel to a “hard contact” such as:
pushbuttons selector switches
By adding a suppression device directly across the coil of an inductive
device, you will prolong the life of the output devices and switch contacts.
Figure 3.24 shows an output module with a suppression device.
Termination Resistor
Surge Suppression