PURPOSE: To obtain a subscriber circuit containing an active inductor circuit which transmits a dial pulse without distortion, by using an MOS transistor of high input impedance characteristics in order to avoid discharge when a subscriber loop is opened.
CONSTITUTION: This circuit has the same function as a conventional circuit as an active inductor and keeps a sufficiently high impedance compared with the impedance of a channel circuit at the band of an audio signal as well as at a frequency band of a switching noise. Thus the noise produced from a current supply source can be prevented. While resistances 8 and 9 of several hundred kΩ∼MΩ are applied to discharge routes 12 and 13 in terms of the dial pulse. A route 11 has a high input impedance of an MOSTR7, and therefore a capacitor 10 has no discharge within the break time of the dial pulse.
MITOMO ISAMU
SHIRASU HIROTOSHI
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