Telephonic communications – Subscriber line or transmission line interface – Hybrid circuit
Patent
1990-06-26
1992-07-21
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Hybrid circuit
379398, 379402, 379391, 379392, H04M 100
Patent
active
051330075
ABSTRACT:
A conversion circuit for connecting a two-wire circuit and a four-wire circuit to each other comprises a transformer having a primary side and a secondary side, the primary side being connected to a two-wire circuit having a variable impedance, a first amplifying circuit having a first input terminal connected to the secondary side of the transformer for receiving an audio frequency signal from the two-wire circuit and a second input terminal, the first amplifying circuit having an output terminal connected to a reception-side line of a four-wire circuit, a second amplifying circuit having an input terminal connected to a transmission-side line of the four-wire circuit and an output terminal connected to the secondary side of the transformer for sending out an audio signal on the transmission-side line to the two-wire circuit, a plurality of impedance matching circuits having respective impedances each determined so as to simulate one state of the variable impedance of the two-wire circuit, and a switch for selectively connecting one of the plurality of impedance matching circuits to the second input terminal of the first amplifying circuit.
REFERENCES:
patent: 4096361 (1978-06-01), Crawford
patent: 4096362 (1978-06-01), Crawford
patent: 4278848 (1981-07-01), Rizzo et al.
patent: 4368361 (1983-01-01), Chung et al.
patent: 4380690 (1983-04-01), Matsufuji et al.
patent: 4498018 (1985-02-01), Lofmark
patent: 4807283 (1984-02-01), Pyhalammi
patent: 5034978 (1991-07-01), Nguyen et al.
patent: 5054062 (1991-10-01), Molner
Augustus Jhancy
Dwyer James L.
Ricoh & Company, Ltd.
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