The SMRG-4 Alarm Relay is a collective alarm component for switching equipment. It is equipped with 4 independent alarm inputs, one phase-assigned switching output for indicator light, as well as one neutral changeover contact for outputting collective alarms to a control room or for an acoustic alarm. Using the SME-12 expansion module increases the number of alarm inputs by 12. Up to 4 SME-12 expansion modules can be connected to an SMRG-4 base component over a 4-pin bus, making a total of 52 alarm inputs available.