Ratings and what they mean for fit
The contact ratings are voltage-dependent — a common reality with auxiliary contacts. At 24 V it switches 2 A; at 230 V it handles 4 A; at 400 V it's rated 3 A; and at 690 V it carries 10 A. The AC-15 rating at 690 V is 1 A, which is the inductive-load limit for that voltage class. That means for a 24 VDC PLC input signal you have headroom to 2 A, but for a 690 V contactor coil you're limited to 1 A. The maximum thermal current is 10 A — that's the absolute limit through the contacts regardless of voltage, so the real-world working current is always the lower of the voltage-specific rating and 10 A. Wire capacity: accepts 2x (0.5 to 2.5 mm²) solid, or 2x (0.5 to 1.5 mm²) with ferruled stranded ends. AWG equivalent is 2x (20 to 14). That's standard for auxiliary wiring in control panels.
Lifecycle reality — phased out, successor known
The 3RV1901-2B is a phased-out product. The official Siemens successor is the 3RV2901-2B, part of the newer SIRIUS 3RV2 family. If you're filling a BOM line for an existing panel, the 3RV1901-2B is still available through independent distribution channels — sourced and quoted to order against an RFQ. For new designs, the 3RV2901-2B is the direct drop-in replacement.
Environmental limits
Operating temperature range is -20 to +60 °C; storage range is -50 to +80 °C. The storage limit is wider because it governs handling and shelf life, not running conditions.