The Emerson DeltaV KJ4001X1-BE1 is an 8-wide I/O Carrier module from the DeltaV series of control systems. 

The KJ4001X1-BE1 module is used as part of the DeltaV system to house and interface with I/O cards. It provides a physical platform for installing up to eight I/O cards, allowing for the expansion of input and output capabilities in the control system.

The I/O cards can be of various types, such as analog input (AI), analog output (AO), digital input (DI), digital output (DO), or specialty modules. The KJ4001X1-BE1 carrier module provides the necessary power and communication connections to these I/O cards and facilitates their integration into the DeltaV system.

By using the KJ4001X1-BE1 carrier module, users can easily expand the I/O capacity of the DeltaV control system, enabling connectivity to a wide range of field devices and providing the ability to monitor and control various process variables.

It's important to note that the specific I/O cards that can be used with the KJ4001X1-BE1 module will depend on the compatibility and configuration requirements of the DeltaV system