The Siemens 3RQ4018-2AN08-0AX0 is a SIRIUS 3RQ4 coupling relay in the narrow 6.2 mm housing. It's an output coupler with an integrated relay, coil rated 110 V DC (0.7-1.25 x Us), and a single change-over contact rated for 6 A thermal current. The spring-loaded push-in terminals speed up wiring in a DIN-rail panel — strip, insert, done. This is a current-production part, actively available.
The 6.2 mm width is the key space-saver here — on a crowded DIN rail, every millimeter matters when you're stacking isolation or signal-conditioning relays for a PLC output bank. The 6 A thermal current covers typical control-circuit loads (solenoids, contactor coils, indicator lamps) without derating in a 40 °C cabinet. The 110 V DC coil with a 0.7-1.25 x Us operating range means it holds in reliably even on a sagging 24 V DC bus stepped up through a converter, or on a battery-backed supply.
Compliance-wise, it's RoHS compliant since 26-09-24, and carries a REACH Article 33 notification for lead (CAS 7439-92-1) above 0.1% w/w — standard for relays with tin-lead plating on certain internal components. Export control is straightforward: AL: N / ECCN: EAR99, no special licensing needed for most destinations.