| 摘要 |
PURPOSE:To make the ordinary reception and muting action selective by using one controlling terminal of an IC by comparing a controlling signal supplied through a controlling terminal with a reference voltage, driving a switching element when a controlling signal different from the controlling signal is supplied and making the signal transmission ineffective. CONSTITUTION:When a switch S1 is turned on, 5th terminal is connected to a voltage V1 through a resistor R24 and current I1 determined by (Vref2-VBEQ17- V1)/R24 is flowed forcibly in a transistor Q17, and correspondingly, the current that flows in a transistor Q16 increases by I1. As only specified current is flowed in the transistor Q18, I1 is flowed in a transistor Q19, and correspondingly, transistors Q20, Q21 become on state. As the current that flows in resistors R5, R9 increases, the voltage drop becomes larger, ad a bias voltage is not more applied to transistors Q11, Q12. Accordingly, an output signal Vout is not obtained by making the switch S1 on, and the muting is executed.
|
