1A Pulse. The Videx 521B is a stabilized power supply with battery backup and is used in access control systems. It is built in a nine modules DIN box type A (157.5mm) which can be installed on a DIN bar or fixed to the wall. . Includes a 13.5Vac 1A output and battery changing output.. PSU 115Vac. Built in a 9 modules DIN box type A.