External power supply in a compact metal housing for up to two 12 V/ 24 Ah batteries. This power supply facilitates an uninterruptable supply of power. Integration into the esserbus/esserbus-PLus optional via optional adapter card (Part No. 805684.10) and esserbus Transponder (Part No. 808623). Four floating relay outputs are available for the transmission of disturbances (power failure, ground fault, battery failure and collective fault). External LED display for operation and collective fault on the lockable front door, internal LEDs for detailed recognition of emergency power operation, individual monitoring of battery failure and ground fault.