Allen-Bradley 440R-D22S2 Guardmaster SS Output Safety Relay

Allen-Bradley Guardmaster 440R-D22S2 Dual Input SS Output Safety Relay (DIS) is a safety monitoring module that accepts two independent, dual‑channel inputs and provides two safety outputs to control safety‑rated loads such as contactors used in machine guarding. The device uses two universal input channels (S11/S12 and S21/S22) compatible with a range of safety devices, enabling two‑channel sensing of protective devices like safety mats, light curtains, or two‑hand controls. Supplied from a nominal 24 V DC source, the 440R-D22S2 integrates safety‑level logic to validate that the monitored circuits are complete before energizing the safety outputs. The DIS configuration includes two safety outputs (SS), which drive the safety contactors K1 and K2 and are designed to be wired in series with the machine guard circuits. The unit also features a built‑in cross‑monitoring scheme where safety status is verified using the S34 circuit to confirm that the linked contactors are off when required, providing fault‑detection capability. As part of the Guardmaster family, it offers robust safety performance in industrial automation environments and is compatible with other Guardmaster safety devices to form compliant safety control circuits.