| 摘要 |
PURPOSE:To remove an equalizing operation error in case when the equalization is impossible, by providing an equalization impossibility detecting circuit, and a circuit for setting all variable attenuators to an initial value by a controlling circuit of the variable attenuator in accordance with an equalization impossibility detecting signal from said detecting circuit. CONSTITUTION:When a carrier reproducing function is stopped in a carrier reproducing circuit 9, an equalization impossibility signal is generated from an equalization imoossibility detecting circuit 10, by which an initial value setting circuit 11 of a variable attenuator. Accordingly, all the variable attenuators are set to an initial value by a controlling circuit 8, and automatic control of the variable attenuator is stopped. As for the initial value, the variable attenuator 2 of a main signal having no direct relation to the equalizing operation is fixed to such attenuation quantity as outputs constant voltage, and as for other variable attenuators 3, 4, the attenuation quantity is set to the maximum and is cut off so that no echo signal is outputted. Also, when the equalization impossibility state is released, leading-in to equalization from said initial value is started, therefore, the equalizing operation is started. |
