Adtran 1175044L1 Wall or rack-mount battery backup system. Supplies 8 hours of uninterrupted backup power to the Total Access 612, 616, 624, 850, 912, 916, 924, 908e, 916e or 924e. The battery backup system can be rackmounted using either 1175047L1 (19in) or 1175048L1 (23in). Requires AC power supply/battery charger (1175043L3) when used with the Total Access 850. NOTE: This product contains lead acid batteries that require regular recharging to prevent degradation during storage.