The Siemens 3RK1105-1AE04-3CA0 is an ASIsafe extended safety monitor with one enabling circuit — a single-channel safe output relay that gates a machine's run permissive. It's a special version of the SIRIUS safety monitor family, built for use up to Category 4 (EN 954-1), PL e (EN ISO 13849-1), and SIL 3 (IEC 61508). That means it's rated for the highest safety integrity levels in a standard industrial safety loop: guarding a robot cell, press, or conveyor zone where a single fault must not cause loss of safety function.
The enabling circuit is a single normally-open relay contact rated at 3 A for AC-12 (250 V) and 3 A for DC-12 (24 V). AC-12 is resistive load switching — think contactor coils or indicator lamps, not motor starts. DC-12 at 24 V covers the same for DC loads. The 50 ms maximum response time means the relay opens within 50 ms of a safety demand, which is standard for guarding applications where a faster (<20 ms) light curtain response isn't needed. The 24 V supply draws 1 A; the 115 V and 230 V auxiliary supplies draw 0.1 A and 0.05 A respectively, so budget that into the control transformer sizing.
The 45 mm width (one standard modular unit) and 120 mm depth fit a typical control panel gutter. Screw terminals for inputs and outputs — field-serviceable with a standard slotted driver. The AS-Interface protocol support means it communicates directly on an AS-i safety network, so it can be addressed and monitored from a safety PLC without hardwired feedback.