LOW VOLTAGE DETECTING DEVICE

PURPOSE:To detect low voltages of many power sources at the same time and to enable cost reduction and a decrease in packaging area by scanning the respective power sources sequentially and periodically and comparing the output voltages of the scanned power sources with a preset value. CONSTITUTION:A CPU 10, a RAM 11, and a memory card 12 are driven by batteries BA1, BA2, and BA3 respectively. The low voltage of the battery BA1 is detected by a detector LB1 and the low voltages of the batteries BA2, BA3, and BA4 are detected by a detector LB2. Then L-level signals are outputted from ports P2, P3, and P4 in order and transistors(TR) TR2, TR3, and TR4 turn on in order, so when the CPU 20 receives the L level from the detector LB2 while the L-level is outputted from, for example, the port P3, it is judged that the voltage of the battery BA3 for the card 12 drops below a prescribed value. Thus, the low voltages of the batteries BA2, BA3, and BA4 are detected by the one detector LB2 at the same time to reduce the cost and decrease the packaging area.