Rockwell Automation T7408 ICS Regent+Plus DC Digital Input Modules 24VDC, 48VDC and 120VDC - Manual (Page 7)

(T7401, 02, and 08) DC Digital Input Modules
P D - 7 0 1 1 M a r - 0 6
7
Keying
The I/O chassis can be physically keyed to prevent accidental
damage caused by inserting a module into a slot wired for a
different module type. Figure 5 illustrates how the slot keys
are installed on the I/O chassis slot field wiring connectors.
The slot key positions for the DC digital input modules are
listed in Table 1.
Figure 5. Installing Slot Keys.