The Siemens 3RQ4018-1AE00 is a SIRIUS 3RQ4 coupling relay — an output coupler with an integrated relay, designed for narrow-panel mounting at 6.2 mm per channel. It switches one change-over contact rated for a thermal current of 6 A, with a 115 V AC/DC coil. The screw-terminal variant lands in standard control cabinets where you need to isolate a PLC digital output from a higher-current or different-voltage load circuit, or to split a signal across two paths.
Where It Sits in the Panel
The 6.2 mm width lets it snap onto a standard DIN rail alongside other SIRIUS 3RQ4 units, packing multiple isolated outputs into a tight enclosure row. Screw terminals accept 0.2–2.5 mm² solid or stranded wire; strip length around 8 mm. The narrow pitch means you can fit roughly 16 of these per 100 mm of rail — useful when a control cabinet needs many dry-contact outputs for valve banks or alarm annunciators.