Mitsubishi Electric Corporation QJ71MB91 Modbus Communication Module

The Mitsubishi Electric MELSEC-Q QJ71MB91 Modbus Communication Module enables MODBUS RTU serial communication between MELSEC-Q PLCs and external devices in both master and slave modes, making it a versatile bridge in industrial automation. It provides a single serial channel over RS-232, RS-422, or RS-485 with data rates up to 115.2 kbps, and supports configurable data formats including parity, stop bits, and baud rate to match various device interfaces. Designed for rack mounting on the Q-series base unit, it maintains compatibility with Mitsubishi MELSEC-Q Series PLCs and supports full master/slave operation for interoperable networked control. Typical uses span SCADA interfaces, energy management, water treatment, HVAC, and factory automation where PLCs coordinate with sensors, variable-frequency drives, meters, and other third-party equipment. Common replacements listed for this module include Mitsubishi QJ71C24N, QJ71C24N-R2, and QJ71E71-100.