| 摘要 |
PURPOSE:To allow a receiver to output a ring tone having a sound volume suitable for surrounding environment by allowing the receiver to detect the surrounding noise to change automatically the operating level of the call tone. CONSTITUTION:When a radio wave including an individual number corresponding to a receiver is irradiated from a base station, the radio wave is received and detected and then fed to a call signal terminal 1. When a tone oscillator 4 is started and a noise detection section 6 is started also in this case, the noise level around the receiver is fetched from a terminal 2 and detected. The information is given to an amplification factor control section 7, which uses the detected information to set the amplification factor of an amplifier 5 inputting an output of the tone oscillator 4. When the surrounding noise is large, the amplification factor of the amplifier 5 is set largely and when almost no surrounding noise exists conversely, the amplification factor of the amplifier 5 is suppressed. As a result, a call tone having a level suitable for the surrounding noise level is outputted from a speaker 3. |
