VA-2000BC is an obligatory unit for Va-2000MA voice evacuation system. It is used to work with battery to provide 24Vdc power supply to complete system, thus battery capacity shall be various from applications. The VA-2000NC DC power supply and battery charger could work stand alone with any public address system as well. There will be usually two units of 12V batteries cascaded together to output 24Vdc for system. It must have capacity to automatically switched into DC mode to support at least 30 minutes of voice evacuation and standby 72 hours once AC power supply failed. While when AC backs, the battery automatically goes into charging mode. Battery capacity, temp and AC/DC failure all will be supervised and status displayed.