US 4,284,859 AGranted

Adaptive electronic hybrid circuit

AssigneeNippon Electric Co., Ltd.

InventorTakashi Araseki

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Abstract

An adaptive hybrid circuit for connecting two-wire and four-wire telephone transmission lines to minimize singing, oscillation or echoes due to impedance mismatch. The circuit comprises a variable impedance circuit connected between the two-wire and four-wire circuits. In one embodiment one end of the variable impedance circuit is connected to the two-wire circuit and to one input of an adder to which the reception signal from the four-wire circuit is also applied and compared in reverse phase and half amplitude. The resulting transmission signal is used to adjust the variable impedance circuit so as to minimize the transmission signal. In another embodiment the variable impedance element is connected to an impedance through which the four-wire reception signal is applied and is further connected to one input of an adder which compares this input in reverse phase with the two-wire signal to produce a transmission signal. This transmission signal is also used to adjust the variable impedance circuit to minimize the transmission signal.

Claims15

Dependent claims

An adaptive electronic hybrid circuit comprising a two-wire terminal for connection to a two-wire circuit, a reception terminal for connection to receive signals from a four-wire circuit and a transmission terminal connected to transmit signals to said four-wire circuit, an adaptive impedance circuit having first, second and third terminals, said adaptive impedance circuit having variable internal impedance characteristics which can be adaptively varied to correspond to the impedance characteristics of said two-wire circuit, an adder connected to add in reverse phase a half value of a reception signal from said reception terminal to a signal from said two-wire terminal to produce a transmission signal on said transmission terminal, said first terminal of said adaptive impedance circuit being connected to said two-wire circuit, said second terminal of said adaptive impedance circuit being connected to said reception terminal and said third terminal of said adaptive impedance circuit being connected to the output of said adder, said adaptive impedance circuit being operative in response to the reception of a signal from said adder which is less than said reception signal to change the impedance of said adaptive impedance circuit to minimize said transmission signal.

An adaptive electronic hybrid circuit comprising a two-wire terminal for connection to a two-wire circuit, a reception terminal for connection to receive signals from a four-wire circuit and a transmission terminal connected to transmit signals to said four-wire circuit, a first impedance element for supplying a reception signal from said reception terminal to said two-wire terminal, an adaptive impedance circuit having first, second and third terminals, said adaptive impedance circuit having variable internal impedance characteristics which can be adaptively varied to correspond to the impedance characteristics of the two-wire circuit, a second impedance element for supplying said reception signal to said first terminal of said adaptive impedance circuit, an adder connected to add in reverse phase the reception signal delivered at said first terminal to a signal from said first impedance element to produce a transmission signal at said transmission terminal, the second terminal of said adaptive impedance circuit being connected to ground, the third terminal of said adaptive impedance circuit being connected to receive the output of said adder, said adaptive impedance circuit being operative in response to the reception of a signal from said adder which is less than said reception signal to change the impedance of said adaptive impedance circuit to minimize said transmission signal.

Dependencies are inferred from the claim text.