The Siemens 3RK1303-5BS44-3AA3 is a reversing starter built for motor control in washdown or dusty environments — the IP65 enclosure keeps moisture and grit out of the contactor and electronics. It runs on 24 V DC control voltage, with a permissible range of 20.4 to 28.8 V DC, so it holds steady on a 24 V bus even with some drop on long cable runs. The solid-state motor protection handles overload sensing internally, no separate relay needed. And it includes brake control at 400 V AC, so it's ready for a motor with a holding brake. On the communication side, it speaks PROFIBUS DP out of the box — no option card needed. No PROFINET onboard, so if your line runs PROFINET, you'll need a gateway or a different variant. The hybrid plug-socket arrangement handles both the supply voltage and the bus connection through a single multi-pin connector, which keeps the wiring clean and saves a couple of cable entries on the gland plate.
Panel fit: 250 mm tall, 130 mm wide, 107 mm deep. The IP65 rating means it's meant to be mounted outside the main control cabinet, close to the motor, with the M12 sockets for the four digital inputs. The hybrid plug for the supply voltage and the hybrid socket for communication are both ISO 23570-style, so the mating connectors are standardised. The four digital inputs are parameterisable — you can assign them to start, stop, reverse, or other functions via the bus. Two of those inputs are on M12 sockets. No digital outputs on board, so any status feedback to the PLC goes over PROFIBUS DP.