| 摘要 |
PROBLEM TO BE SOLVED: To start talking only through opening operation by judging whether a folding type portable telephone set is in folded state or in opened state through photodetection. SOLUTION: When call incoming is detected by a control part 3, a photodetection part 2 detects the light of a light emission part 1 and monitors whether a photodetecting signal is transmitted to the control part 3 or not. When the photodetection part 2 detects the light of the light emission part 1 and transmits it to the control part 3, since a portable telephone set 20 is in the closed state, the control part 3 judges whether a talking start key 4a is pressed or not and when it is detected this key is pressed, the light emission part 1 is turned off. At the same time, a ring back tone or vibration stops. When the photodetection part 2 stops detecting the light of the light emission part 1, it is time when a user knows call incoming and opens the portable telephone set 20 and even without pressing the talking start key 4 or 4a, a talking mode is started.
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