| 摘要 |
PURPOSE:To prevent effect of a click voltage and to attain clear loudspeaking by setting a gain control voltage of an automatic gain control circuit of a reception loudspeaking circuit to a proper value within a prescribed period including a sending period of a dial signal. CONSTITUTION:In operating a sending switch 22, a switching contact 3 is thrown to the position of the reception loudspeaker circuit 10' and a dial tone is incoming. In operating a dial switch 23 in this state, contacts 2a, 2b are switched and a dial pulse is sent to a subscriber line 1. When a ring back tone and a reception signal comes from an exchange, they are subject to level control by the automatic gain control circuit 12 of the circuit 10' and the result is outputted from a speaker 11 with a proper sound volume. Since a capacitor 17 holding the level control voltage of the circuit 12 is in a discharge state for a prescribed period including the sending period of the dial signal by a switch 18, no adverse effect due to a click voltage is imposed.
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