This DIN rail-mounting power supply unit features SPCO relay monitoring contacts, output controls and battery support. This unit will seamlessly switch from mains power input to battery powered input in the event of a mains power failure. If this occurs, the unit will also change over SPCO relay contacts for switching or signalling to other equipment that the mains supply to this power supply unit has failed. When mains power is restored, the unit will change over the monitoring relay contacts and automatically re-charge the connected VRLA battery.

During prolonged mains power failure, if the connected VRLA battery is nearing depletion, the 'Low volt' SPCO relay contact will change over to switch or signal to other equipment that the battery power is nearly depleted.