It will be used when emergency operation is required, in the event of a power cut. Along with this adapter a 12 Vdc power supply and the necessary battery are used to supply the voltage and current required by the installation, (battery not included with the adapter). If the voltage drops below 11Vdc it automatically switches to the battery. This adapter supports any type of standard lead acid battery. It is mainly used in video door entry installations of the Fermax MDS and Access Control systems. It will be used when emergency operation is required in the installation. It has a DIN 6 rail format, to facilitate its installation inside an electrical equipment box, or it can be screwed directly onto the wall. It is built in self-extinguishing VO material.