Allen-Bradley 440R-EM4R2 Monitoring Safety Relay

The Allen-Bradley Guardmaster 440R-EM4R2 Monitoring Safety Relay is an expansion module (EM) for Guardmaster safety circuits that provides a single-wire input interface and a dedicated safety output. It accepts a single-wire safety signal via terminals L11–L12 to instruct the EM to turn on or off as part of a monitored safety loop, enabling you to extend guard monitoring beyond the primary safety relay. This module delivers one normally closed (NC) contact to signal a safe or failed-state in the monitored circuit, making it suitable for interlocks, guarded access doors, and other single-channel safety devices that need independent monitoring within a Guardmaster system. The EM4R2 is designed as a Guardmaster expansion module and is typically used alongside Guardmaster safety relays (MSR/GSR families) to build multi-channel safety networks, with a compact footprint and IP40-rated housing for basic industrial environments. Common configurations place the 440R-EM4R2 as the remote input module for additional devices, enabling simple integration into existing safety circuits without rewiring the primary safety controller. In practice, it supports the Guardmaster approach of using single-wire safety interfaces to monitor a device’s state while isolating it from the main safety logic, helping ensure reliable fault detection and safe shutdown in machines such as presses, conveyors, and other automated equipment.