The Siemens 3RK1105-1AG04-0CA0 is an ASIsafe Basis safety monitor with one enabling circuit and one safe relay output. It's designed to supervise safety functions on an AS-Interface safety network, providing a monitored output that can be wired into the machine's safety chain. The response time is a maximum of 40 ms, which means the output drops within that window after the input condition is lost — fast enough for most guarding applications up to Category 4 (EN 954-1), PL e (EN ISO 13849-1), and SIL 3 (IEC 61508). That's the top end for a single-channel safety monitor in this form factor.
The safe output is rated for 3 A at 24 V DC in DC-12 (DC-1) duty, and 3 A at 250 V AC in AC-12 duty. AC-12 is the resistive-load category — think solenoids, signal lamps, or contactor coils with no significant inrush. If you're switching an inductive load like a small motor contactor, you'll need to check the inrush against the AC-15 or DC-13 rating (not listed here; the part is a safety monitor, not a power contactor). The 24 V control supply draws 1 A; the 115 V and 230 V control options draw 0.1 A and 0.05 A respectively — that's the current the AS-Interface bus or an external 24 V supply must deliver to keep the monitor alive.
Width is 45 mm — that's three modular units on a standard DIN rail, so it takes up the same slot as a typical three-pole miniature circuit breaker.