| 摘要 |
PROBLEM TO BE SOLVED: To reduce the consumption of a battery by eliminating excessive supervisory in the case of monitoring a call from a center side device from the detection of a certain signal to the detection of the next signal. SOLUTION: When calling is started from the center side device and a pole inversion is detected, the detection of the next preringer is monitored and at the same time, the measurement of time is started. When the preringer is detected, that time is stored in a memory. Afterwards, the telephone number and ringer of a caller are successively detected and communication with the center side device is performed. Since supervisory time is set on the basis of the measured time, supervisory is enabled just for proper time.
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