The Siemens 3RQ4018-1AB01 is an output coupler from the SIRIUS 3RQ4 family, built in a narrow 6.2 mm housing. It integrates a relay with a 24 V AC/DC coil and one change-over contact rated for 6 A thermal current. The contacts are hard gold-plated, which suits low-level switching where oxidation on standard contacts can cause intermittent faults. Screw terminals keep wiring straightforward for panel builders.
The 6 A thermal current covers typical signal-level loads like PLC outputs or small contactor coils. The 24 V AC/DC coil means it works on either supply without a separate rectifier, simplifying panel wiring.