The Siemens 3RH2911-4DA11 is a SIRIUS lateral auxiliary switch block designed to snap onto the left or right side of a 3RT2 contactor. It gives you one normally-open and one normally-closed instantaneous contact, with ring-tongue terminals for the control wiring. This is the add-on that lets a power contactor report its state back to a PLC or safety circuit. The contacts are rated for a maximum of 10 A, with the actual current-carrying capacity depending on the voltage and duty cycle — at 24 V it handles 6 A (AC-15), at 230 V it also handles 6 A, and at 400 V it drops to 3 A. For DC switching, the ratings are lower: 10 A at 24 V, 4.7 A at 60 V, and 0.26 A at 600 V. That matters when you're feeding a 24 VDC PLC input on a conveyor line.
The block is 10 mm wide, 85.4 mm tall, and 43.7 mm deep — it adds barely a finger's width to the contactor assembly. The front is IP00, so it lives inside an enclosure; no washdown exposure out here in the grease. Termination is via ring-tongue lugs on the control circuit. That's a field-proven connection for maintenance crews — no tiny spring-cage to fight with gloved hands. Strip, crimp, torque, and it stays put through vibration.
No official successor has been announced — this is the active design.