What action must be taken for input devices when replacing them in a ControlLogix system?

In a ControlLogix system, when replacing input devices, the action required is compatible keying. This ensures that the replacement device can interface correctly with the existing system without mismatched connections that could lead to operational issues or system faults.

Compatible keying allows for different but compatible devices to be used interchangeably. This means that while the physical connections may not be identical, they adhere to a set of standards that allows the system to accept various types of devices based on their functionality rather than their specific configuration. This approach enhances flexibility in maintenance and upgrades, allowing engineers to source devices that may not be exact matches but still meet operational requirements.

The other approaches, such as exact match keying, would require that only identical devices could be swapped, limiting the options for replacement and potentially causing longer downtime. No keying would allow any device to connect, risking improper connections and system failure. Disabling keying would negate safety measures that prevent incorrect devices from being connected, further jeopardizing system integrity. Thus, using compatible keying provides a balance between flexibility and safety, making it the preferred method for replacing input devices in a ControlLogix environment.