Rockwell Automation T7420A_AF ICS Regent+Plus Analog Input Modules 60Hz Rejection and Fast Response - Manual (Page 14)

Analog Input Modules (T7420A, AF)
1 4
Industrial Control Services
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 7 illustrates how the slot keys
are installed on the I/O chassis slot field wiring connectors.
The slot key positions for the analog input modules are listed
in Table 4.
Figure 7. Installing Slot Keys.