Acroprint 58-0108-000 Optional Back-Up Ni-Cd Battery Pack, 8.4 Volts, 700mAH, For Use with ES900 Atomic Time Recorder and ES1000 Atomic Payroll Recorder Allows punching when the power is off For use with the ES900 Atomic Time Recorder For use with the ES1000 Atomic Payroll Recorder Voltage: 8.4V Amperage: 700mAh