Telephonic communications – Line equalization or impedance matching
Patent
1987-09-23
1988-12-13
LaRoche, Eugene R.
Telephonic communications
Line equalization or impedance matching
379400, H04B 336
Patent
active
047916680
ABSTRACT:
An interface circuit a.c. couples a transmission line and a port of a telecommunications facility. The transmission line may be of any of n characteristic impedances. The interface circuit includes a resistor network having at least 2n+1 resistor elements. The resistor network is connected to ground by at least one of the resistor elements. A switching device includes at least n switching elements being connected between n of the resistor elements and an input of an amplifier. A transformer includes first, second and third windings, the first winding being for connection to the transmission line, the second winding being connected between an output of the amplifier and a junction between the one of the resistor elements and at least another of the resistor elements, and the third winding being connected between ground and a point in the resistance network other than the junction. A resistor connects at least one of the n switching elements and the port of the telecommunication facility. A control device is connected to the switching device for controlling each of said switching elements to be of one of a high resistance state and a lower resistance state. In one example, each of the switching elements consists of a semiconductor which includes at least one field effect transistor.
REFERENCES:
patent: 2864901 (1958-12-01), Aigrain et al.
patent: 3919502 (1975-11-01), Daryanani
patent: 4027114 (1977-05-01), Kahlbrock
patent: 4096361 (1978-06-01), Crawford
patent: 4682355 (1987-07-01), Bailly
LaRoche Eugene R.
Lee Benny
Moorhouse J. E.
Northern Telecom Limited
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