What this module is, in panel terms
The Mitsubishi LJ71E71-100 is an Ethernet communication interface module built for MELSEC L series programmable logic controller systems, providing TCP/IP industrial networking as a dedicated expansion slot on the L-series backplane. It lives in the PLC Expansion Modules category under PLCs and Accessories, so it slots into the same DIN-rail footprint and base unit architecture as the other L-series I/O and communication cards.