| 摘要 |
PROBLEM TO BE SOLVED: To allow the user to hear well a call tone from the outside of a bag or the like even when a portable telephone set is contained in the bag or the like. SOLUTION: When a specific key placed on an outside of a case is depressed or power is energized and a light receiving element 4 detects a light, a test tone is outputted from a speaker 7, its echo sound is picked up by a microphone 5 and a control circuit 3 stores the tone volume as a reference volume to a memory 6. Upon the receipt of a received call from a transmission reception circuit 2 and the light receiving element 4 does not detect the light, a test tone is outputted from the speaker 1 and the echo sound is picked up by the microphone 5 and the tone volume is compared with the reference value stored in the memory 6. The control circuit 3 increases the tone volume of the call tone outputted from the speaker 7 when the tone volume of the echo tone is larger than the reference volume, the control circuit 3 increases the tone volume of the call tone outputted from the speaker 7. The detection result of the light emitting element 4 is changed from the light non-detection to the already detected result, the control circuit 3 selects blinking by a light emitting diode 8 from an output of the call tone by the speaker 7.
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