The Mitsubishi QJ61BT11N-CC is a master/local module for the Q-series PLC platform. It handles network communication between a master station and remote I/O stations on the same fieldbus link. This is a mature, established part — still listed in Mitsubishi's current catalog, not flagged for discontinuation.
The QJ61BT11N-CC is classified as a mature product.
Not a direct swap with Ethernet modules
If you are wondering whether the LJ71E71-100 Ethernet module can stand in for this part — no, it cannot. The QJ61BT11N-CC is a fieldbus master/local module, not an Ethernet interface. They perform different network-layer functions and are not pin-compatible or software-interchangeable. Stick with the correct order code for your system's network architecture.