| 摘要 |
PURPOSE:To prevent a decrease in peak margin and to suppress an increase in current consumption by lowing the sound volume level of a device which uses an AC and a battery power sources in battery operation automatically. CONSTITUTION:When AC electric power applied to an input terminal 1 is used, an AC detecting circuit 11 controls an attenuator 12 and the output of a preamplifier 7 is applied to a sound volume controller 8 without attenuation. When the electromotive force of a battery 3 is used instead of the AC electric power, the attenuator 12 is controlled to supply a signal attenuated to a level conforming to the capacity of the power source to a power amplifier 9 through the sound volume controller 8. Thus, the sound volume level in the battery operation is lowered automatically to prevent a decrease in peak margin and suppress an increase in power consumption. |
