Patent ID: 7610501

Claim:
An electronic device comprising: a security region containing a plurality of security components, said security region being surrounded by a mechanical security barrier to normally preclude physical access to said security components; a power source adapted for connection to a mains voltage for normally supplying power to said security components; a first battery disposed in said security region with physical access to said first battery also being normally precluded in said security barrier; a second battery disposed outside of said security region for supplying power to said security components upon an outage of said mains voltage; a battery switchover device having a first input connected to said first battery and a second input connected to said second battery and an output, said battery switchover device switching power supply to said security components from said second battery to said first battery only if power from said second battery is absent; a monitoring unit disposed in said security region and connected to said battery switchover device, said monitoring unit for evaluating voltage information associated with at least one of a voltage of said first battery and a voltage of said second battery; said monitoring unit comprising an analog-to-digital converter that converts said voltage information into digital information, said analog-to-digital converter having a first input and a second input; and a first series circuit of Schottky diodes connected between said first input of said battery switchover device and said output, and a second series circuit of Schottky diodes connected between said second input of said battery switchover device and said output, said first series circuit having a center tap connected to said first input of said analog-to-digital converter and said second series circuit having a center tap connected to said second input of said analog-to-digital converter.