Telephonic communications – Subscriber line or transmission line interface – Network interface device
Patent
1992-09-03
1994-09-13
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Network interface device
379399, 379324, 379405, H04M 1900
Patent
active
053475771
ABSTRACT:
A battery feed circuit supplies a feed current to a telephone set via a 2-wire telecommunication line formed of a TIP line and a RING line. The battery feed circuit includes a first voltage detection circuit for detecting a first voltage across the TIP line and a ground line, a second voltage detection circuit for detecting a second voltage across the RING line and a power line connected to a power supply of the battery feed circuit, a current source responsive to a first control signal for respectively generating first and second currents in the TIP and RING lines, the first and second currents being equal in magnitude and opposite in direction, the current source also varying the first and second currents in response to a second control signal so as to be in proportion to a common mode voltage across the TIP and RING lines, a first feedback circuit responsive to the first and second voltages detected by the first and second voltage detection circuits for generating the first control signal, and a second feedback circuit for generating the second control signal by detecting the common mode voltage across the TIP and RING lines.
REFERENCES:
patent: 4476350 (1984-10-01), Aull et al.
patent: 4872199 (1989-10-01), Kawami et al.
patent: 4935960 (1990-06-01), Takato et al.
patent: 4982422 (1991-01-01), Itoh et al.
Minohara Kazuyuki
Takato Kenji
Yoshida Kazuhiro
Dwyer James L.
Fournier Paul
Fujitsu Limited
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