Patent
1980-02-25
1982-03-09
Konick, Bernard
179 81R, H04M 1900
Patent
active
043190944
ABSTRACT:
A three-terminal power supply circuit for telephone set has an input terminal, an output terminal and a common terminal. The input terminal receives a DC voltage superposed with a sending or receiving signal transmitted to or from a telephone station through a subscriber line. The output terminal delivers DC power to a telephone circuit. Between the input and output terminals a constant current circuit and a discharge protection circuit are connected to each other in series. Between the output terminal and the common terminal a constant voltage circuit is connected. Between the input terminal and the common terminal an electronic switch is connected through the constant current circuit. The electronic switch is closed only when an instantaneous voltage applied between the input terminal and the common terminal is lowered to a predetermined value or a lower value. When it is closed, the electronic switch causes a short circuit in the constant voltage circuit through discharge protection circuit. This lowers the cutoff voltage applied on the input side of the power supply circuit, and both a sending signal and a receiving signal can be transmitted without being distorted.
REFERENCES:
patent: 3708630 (1973-01-01), Matsuda et al.
patent: 3800095 (1974-03-01), Cowpland
Kato Kunihiro
Naganawa Tatsuhiro
Yoshitoshi Makoto
Konick Bernard
Nippon Telegraph & Telephone Public Corporation
Popek J. A.
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