| 摘要 |
PURPOSE:To allow the muting signal generating circuit to operate with a low- voltage power source by providing a means which mixes currents flowing through two transistors (TR) which turn on according to the level of a detection output signal. CONSTITUTION:When the plus-side voltage of the detection output signal is impressed to an input terminal 9, a TR10 turns on and the collector current is inverted by current inverting circuits 16 and 22 to develop a voltage corresponding to the output current of the inverting circuit 22 at one terminal of a resistance 25. When the minus-side voltage of the detection output signal is impressed, on the other hand, a TR12 turns on and its collector current is inverted by a current inverting circuit 19 to develop a voltage corresponding to the output current of the inverting circuit 19 at one terminal of the resistance 25. When the voltage at one terminal of the resistance 25 exceeds a specific value, an output TR27 turns on and an output signal as a muting signal appears at an output terminal 28. This muting signal generating circuit operates with the low voltage power source.
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