The Siemens 3RH1921-1DA11-ZX95 is an auxiliary switch block with one normally-open and one normally-closed contact, designed for lateral mounting on Siemens motor contactors in sizes S0 through S12. It uses screw terminals and conforms to the DIN EN50012 mounting standard, meaning it snaps onto the contactor side at a 10 mm pitch without additional brackets.
Mounting and integration notes
The block mounts laterally to the contactor — not on top — so it does not occupy the auxiliary terminal space used for other add-on modules. Verify the contactor frame size (S0 through S12) matches before ordering; the block will not fit larger S14 or S20 frames.