| 摘要 |
PROBLEM TO BE SOLVED: To enable speech communication by means of a bone conduction speaker with a simple structure. SOLUTION: When an ordinary speaker 21 is connected to a telephone device, the capacitor 102 side of a pull-up resistor 103 becomes a low level. On detecting the low level, a control unit 40 does not change the amplification degree of an amplifier 101. On the other hand, when a bone conduction speaker 31 is connected to the telephone device, the capacitor 102 side of the pull-up resistor 103 becomes a high level. On detecting the high level, the control unit 40 increases the amplification degree of the amplifier 101. In such a manner, when the bone conduction speaker 31 is connected to the telephone device, the telephone device automatically increases the amplification degree of the amplifier provided in the telephone device. COPYRIGHT: (C)2011,JPO&INPIT
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