60 I/O points, DC-powered, relay output — the panel fit
The FX3G-60MR/DS is a Mitsubishi Electric FX3G series PLC main unit with 60 total input and output points — that's the I/O count you design the machine control around, not an expandable rack but a fixed-configuration controller for applications that fit within that footprint. It runs on DC power supply with 24 VDC sink/source inputs and relay outputs, meaning the field wiring connects directly to the terminal block without an external interface module — common for standalone machine control where the panel already has a 24 VDC bus.
What the I/O type means for your panel
The R/DS designation tells you the output side uses relay contacts rather than transistors — relay outputs handle AC and DC loads up to the contact rating, tolerate inrush from solenoids and contactors, and isolate the PLC from the load circuit galvanically. The trade-off is slower switching speed compared to transistor outputs, but for most discrete control applications (conveyors, packaging, material handling) the relay response is adequate. Inputs are sink/source compatible (24 VDC), so you can wire NPN or PNP sensors without a polarity converter — the PLC accepts either as long as the common is wired correctly.