It will be used when emergency operation is required, in the event of a power cut. Along with this adapter an 18 Vdc power supply and the necessary batteries are used to supply the voltage and current required by the installation, (batteries not included with the adapter). 2 standard 12V lead acid batteries of the required amperage must be connected. It is mainly used in video door entry installations of Fermax's ADS, MDS and 4 + N systems. It has two operating indicator LEDs: - GREEN LED on: Normal Operation. - RED Led on: Emergency Operation. It will be used when emergency operation is required in the installation. It has a DIN 10 rail format, to facilitate its installation inside an electrical equipment box, or they can be screwed directly onto the wall. It is built in self-extinguishing VO material.