What it is and what it drives
The Mitsubishi MR-J4W3-444B is a digital AC servo amplifier from the MELSERVO-J4 Series, controlling two axes at 0.4 kW rated output each. It communicates over SSCNETIII/H, the high-speed synchronous motion bus that ties it to a compatible controller without pulse-train wiring or analog tach feedback. That means the loop closure and tuning happen inside the drive, not the PLC — useful when you need coordinated multi-axis moves over a single cable.
