The Siemens 3RQ4070-2SG30 is a SIRIUS 3RQ4 coupling relay in the narrow 6.2 mm housing. It uses an input optocoupler rated for 110-230 V AC/DC, giving you galvanic isolation between the control circuit and the load side. The single normally-open (NO) contact is rated for a thermal current of 5 A, which is the continuous current the contact can carry in free air — not the switching current under load, which will be lower depending on the load type and duty cycle. The spring-loaded push-in terminal (Siemens calls it push-in) accepts solid or ferruled stranded wire without a tool, which speeds panel wiring.
That narrow footprint matters when you're packing multiple isolation points into a control cabinet — you can fit roughly 16 of these per 100 mm of rail. The push-in terminals face forward, so wiring density is limited more by wire bend radius than by the terminal spacing. The packaging dimensions are 95 x 93 x 65 mm for the individual unit, but the installed depth on the rail is shallower — the 6.2 mm width is the panel-space figure to budget.
It is RoHS compliant since 26 September 2024, and carries a REACH Article 33 duty-to-inform notification for lead (CAS 7439-92-1) above 0.1% w/w — standard for electronic components with solder joints.