The Q65B is a 5-slot extension base unit for Mitsubishi's Q Series programmable logic controllers. One of those slots is dedicated to the power supply module, leaving four slots free for CPU, I/O, or special-function modules. It accepts any standard Q Series module, so the slot layout follows the same backplane rules as the main base — no special mapping required.
What the Slot Count Means for Your Panel
Five slots total, one reserved for the power supply. That gives you four usable slots for the rest of the system. In a typical Q Series rack, the CPU occupies slot 0 (closest to the power supply), leaving three slots for I/O or special modules. If your design calls for more than three I/O slices plus a CPU, you either need a larger base (like the Q68B with eight slots) or a second extension base daisy-chained via the extension cable. The physical dimensions — 37 cm long, 12.5 cm deep, 6 cm high — fit a standard 600 mm deep enclosure with room for wiring ducts on either side.