| 摘要 |
PROBLEM TO BE SOLVED: To attain low power consumption in a terminal equipment for a meter in an automatic meter reading system. SOLUTION: This is a terminal equipment for a meter, in which the power supply voltage polarity of a telephone line is detected, an incoming call at the time of no-ringing calling or ringing calling is detected, a CPU circuit part is activated, and a meter reading value is transmitted to a center terminal equipment. A polarity inversion detecting circuit 1 for detecting the power supply voltage polarity of the telephone line is constituted of a polarity detecting part 3 having first and second photocouplers PC1 and PC2 for detecting the voltage polarities of both power supply voltages, and a power source controlling part 4. Thus, power supplying to the light-receiving element of the first photo-coupler PC1 is stopped, and power supplying to the light-receiving element of the second photo-coupler PC2 is started in accordance with the detection signal of one voltage polarity of the light-receiving element of the first photocoupler PC1. Also, power supplying to the light-receiving element of the second photocoupler PC2 is sopped, and power supplying to the light-receiving element of the first photocoupler PC1 is started in accordance with the detection signal of the other voltage polarity from the light-receiving element of the second photocoupler PC2. Then, the polarity inversion detection signal of the power supply voltage is added to a CPU circuit part 2.
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