What the key ratings mean for fit
The 3SK1220-2AB40: The 24 V DC rated supply is the standard control voltage for this safety relay family — it powers the internal logic and sensor monitoring circuits. The 17.5 mm width means it occupies a single modular DIN-rail slot, so it fits tightly in crowded panels alongside contactors or other SIRIUS components. The push-in spring terminals accept solid or stranded wire from 20 to 16 AWG, and with ferrule processing from 0.5 to 1.0 mm², which matches typical control wiring practice for safety circuits.
Configurable safety functions
This module is parameterizable for multiple sensor configurations: floating or non-floating sensors, monitored or automatic start-up, 1-channel or 2-channel sensor connection, cross-circuit detection, startup testing, antivalent sensors, and 2-hand switches. This flexibility lets it adapt to different safety architectures — e.g., a light curtain with OSSD outputs or dual-channel emergency stop buttons — without hardware changes.
Environmental and mounting considerations
The relay mounts via screw and snap-on fastening to a DIN rail, with any mounting position allowed. Operating temperature range is -25 to +60 °C, storage from -40 to +80 °C. It withstands shock at 10g / 11 ms and is rated for pollution degree 3 and overvoltage category III — suitable for industrial control panels where conductive dust or humidity may be present. Relative humidity during operation can be 10 to 95 %.