| 摘要 |
PURPOSE:To provide compatibility to a speaker unit by using an external control signal so as to control a variable impedance element being a component to >=one side of a bridge circuit thereby obtaining automatically an exact velocity signal. CONSTITUTION:The impedance value of the variable impedance element 16 is controlled to an optional value by a control voltage Vc from control signal generating circuit 17. That is, when a switch 15 is thrown to the position A and a switch 15' is thrown to the position D, a proper signal is inputted to the bridge circuit from a signal generating circuit 18, the control voltage Vc is generated by the control signal generating circuit 17 from the output of a differential amplifier 9 and the variable impedance element 16 is controlled so that the output of the differential amplifier 9 is a desired characteristic. Thus, the bridge circuit is adjusted automatically to an optional speaker unit 8 and the compatibility is given to the speaker unit 8. |
