| 摘要 |
PURPOSE:To send a ring tone with a level always proper to the user by adjusting automatically the ring tone volume depending on the condition of surrounding noise. CONSTITUTION:The surrounding noise detected by a microphone 3 is amplified and converted into a DC potential and held by a holding circuit 13 controlled by an output of an incoming signal detecting circuit 1. When a ring tone rings, it is not detected as the surrounding noise. Thus, the output of the circuit 13 is inputted to a control voltage generating circuit 14, where the output is converted into a DC bias voltage changing the signal to control a ring tone ringing circuit 2. Further, a 16Hz oscillator 9 is driven by the output of the incoming signal detecting circuit 1 in the ring tone ringing circuit 2, amplified by a variable gain amplifier 10, a bell circuit 11 is operated by the output to ring the ring tone. Since the ring tone volume is proportional to the output of the amplifier 10 and the gain of the amplifier 10 is changed depending on the output voltage of the circuit 14, the ring tone volume is proportional to the output voltage of the circuit 13.
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