Terminal impedance setting circuit for a two-wire to four-wire c

Details Terminal impedance setting circuit for a two-wire to four-wire c Terminal impedance setting circuit for a two-wire to four-wire c

1988-11-23

1990-04-17

Schreyer, Stafford D.

Telephonic communications

Substation or terminal circuitry

Impedance matching or line equalizing

379398, 379345, H04M 176, H04B 166

Patent

active

049187252

ABSTRACT:
A terminal impedance setting circuit in a 2- to 4-wire converting circuit allows the characteristic impedance to be changed with accuracy while enhancing a miniaturization of the converting circuit. The impedance setting circuit has a first amplifier for amplifying signals that are incoming over a send pair of a four wire line and are destined for a two wire trunk line. A second amplifier amplifies signals that are incoming over the two wire trunk line and are destined for a receive pair of the four wire line. A resistor network is associated with each of the amplifiers for adjusting the output thereof. A shunt resistance is coupled between an input of the first amplifier and an output of the second amplifier for matching the impedance of the two wire trunk line. A semiconductor switch adjusts the resistances of the resistor networks and the shunt resistance in response to an external command.

REFERENCES:
patent: 4503289 (1985-05-01), Spires
patent: 4791668 (1988-12-01), Pringle

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