The Siemens 3RQ4052-2SM50 is an output optocoupler from the SIRIUS 3RQ4 series of coupling relays in the narrow 6.2 mm housing. It switches a single normally-open contact rated for a thermal current of 2 A, controlled by a 24 V DC input.
At 6.2 mm wide, this coupling relay occupies minimal DIN-rail space — useful when isolating a PLC digital output from a downstream load or signal conditioning in a crowded control cabinet. The 24 V DC coil side is optically isolated from the contact side, so it can separate control and power circuits within the same enclosure without shared ground loops.
What the 2 A rating means
The 2 A thermal current (Ith) is the continuous carry rating at ambient temperature — it governs the maximum steady-state load through the contact. For switching inductive loads like small relays or solenoid valves, derate below that figure; the optocoupler's semiconductor output handles the switching, not a mechanical contact, so no arc-erosion wear to track over cycles.