What it is and what it does
The Siemens 3RK1405-1BG00-0AA2 is an ASIsafe SlimLine safety module — part of the SIRIUS family — that brings two safe digital inputs and two standard solid-state outputs into a 22.5 mm wide housing. It's built for integrating mechanical safety switches (like interlock or limit switches) into an AS-Interface safety network, where the safe inputs monitor the guard position and the outputs switch standard 24 V DC loads downstream. The module handles the safety logic over the AS-i bus, so it doesn't need a separate safety relay for each zone. The two safe inputs are designed for mechanical switching contacts — think door switches or emergency-stop buttons with dry contacts. Each input draws a minimum of 5 mA at signal "1" (contact closed), which is enough to wet the contacts and keep oxidation from causing nuisance faults out on the factory floor. The built-in watchdog and short-circuit protection mean the module self-checks for faults and won't latch up if a sensor wire gets pinched.
Where it fits in the panel
This module snaps onto a standard 35 mm DIN rail (EN 50022) or mounts directly to a panel backplate. At 22.5 mm wide and 91 mm deep, it tucks into tight wireways alongside other SlimLine blocks — you can pack several safety zones into a single row without chewing up cabinet real estate. The spring-loaded terminals accept solid or ferruled stranded wire up to 2.5 mm², which is the usual gauge for control wiring in a machine cabinet. IP20 protection means it's for dry indoor cabinets only — no washdown, no dust-laden environments. The operating temperature range of -25 to +70 °C covers most control rooms and machine enclosures, and storage tolerance down to -40 °C means it can sit on a spare-parts shelf in an unheated warehouse.
AS-Interface bus integration
Power and data come over the AS-Interface cable at 26.5 to 31.5 V DC. The module draws a maximum of 60 mA from the AS-i bus, which is modest — you can run several of these on a single segment without overloading the AS-i power supply. The two standard outputs get their 24 V DC load power from the auxiliary AUX lines, not from the bus, so the safety outputs aren't limited by the bus current budget. Addressing is done through the front socket, and the module uses ID/ID2 codes B/F. The yellow LEDs show I/O status; the green/red LED indicates AS-Interface communication and diagnostics. If the bus goes down, the watchdog trips the safe outputs to a defined off-state.