| 摘要 |
PURPOSE:To prevent the sudden generation of sound and to eliminate the shock or unpleasant feeling of a user by forming an integration circuit so that the gain of an amplifier is minimum when a power supply is applied, then gradually increased. CONSTITUTION:A control voltage generator 27 produces a voltage signal which varies stepwise in response to the output fed from a touch sensor 26. An integration circuit 28 integrates the step-type voltage signal fed from a control voltage generator 27 and outputs a voltage signal which increases gradually after an earpiece is put on. An amplifier 24 consists of a voltage control type amplifier, and the gain of the amplifier 24 is controlled by the output voltage signal of the circuit 28. As a result, the gain of the amplifier 24 is set minimum when the power is supplied and then increased gradually. This prevents the sudden generation of sound or unpleasant feeling which is produced when a hearing aid is put on or by a misoperation of the earpiece. |
