| 摘要 |
PURPOSE:To prevent a calling voice from being unheard by controlling the sound volume of a speaker to be a large sound volume at the reception of the calling signal independently of the setting of a sound volume adjusting device. CONSTITUTION:A calling station 1 operates a control signal transmitter 6 ahead the voice calling to send a control signal. When a control signal receiver 7 of a called station 2 detects the control signal, a count start signal is fed to a timer 8. The timer 8 supplies a sound volume control signal to a sound volume controller 9 during the set count time. The sound controller 9 sets the sound volume of a speaker 5 to a large sound volume independently of the sound volume setting state of a sound volume adjusting device 4 during the input of the sound volume control signal. As a result, since the calling is outputted from the called station by a large sound volume, the unheared calling sound is prevented.
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