Method of indicating operation of backup battery and circuit for sensing the same

摘要

A circuit and a method of indicating the operation of a backup battery used in a communication device use a sensing circuit. The sensing circuit includes a diode connected in the forward direction between the communication device and the backup battery, for forming a current path from the communication device to the backup battery. A photocoupler connects in the forward direction between the backup battery and the communication device, for forming a current path from the backup battery to the communication device and sensing an output voltage from the backup battery. When the backup battery is operated, such a situation is sensed and the user is informed.