| 摘要 |
PURPOSE:To decrease the number of circuit elements, and to easily execute the integration, by setting the constant number of elements of the first and second attenuation step circuits so that an impedance value seen from an input terminal becomes constant at all times, and inserting a correcting resistor as necessary. CONSTITUTION:A sound signal input terminal 1 is connected to an input terminal of the first attenuation step circuit 2, and this input terminal is grounded by a series circuit consisting of an electronic control type connection switch 8, an input impedance correcting resistor 9 and resistors 2a-2c. Also, the input terminal of the circuit 2, a connecting point of the resistor 9 and 2b, and a connecting point of the resistor 2b and 2c are connected to electronic type connection switches 3a-3c, respectively, and through these switches 3a-3c is connected the input terminal of the second attenuating circuit 5 to the output terminal of the circuit 2. On this circuit 5 are provided resistors 5a-5h and electronic type connection switches 7a-7h, and the switches 7a-7h are connected to an output terminal 6 of the circuit 5. In this way, the impedance seen from the input terminal 1 is made constant at all times, and the number of circuit elements is decreased. |
