Allen-Bradley 440R-B23020 Single Function Monitoring Safety Relay

Allen-Bradley 440R-B23020 Guardmaster MSR5T is a single-function monitoring safety relay designed to supervise one safety circuit in machine-control applications. It operates from 24 V AC/DC and accepts two normally closed safety inputs, then provides three normally open safety outputs plus one normally closed auxiliary output to carry fault- and status-signaling signals to safety controllers or PLCs. Field wiring uses removable screw-terminal blocks, and the unit supports both automatic and manual reset to fit different safety workflows. As part of Rockwell Automation’s Guardmaster 440R family, the MSR5T is intended for monitoring devices such as emergency-stop switches, interlocks, and other single-channel protective devices within a single safety function, delivering a monitored output that confirms a fault-free path when all inputs are safe. Typical applications include safeguarding hazardous machinery zones, controlling safety-rated stop functions, and enabling straightforward safety circuits where a single monitored channel suffices. The 440R-B23020 designation identifies the MSR5T single-function safety relay with the described input/output configuration and 24 V power requirement, making it a compact, field-wiring-friendly option for compliant safety monitoring in moderate-complexity machinery.