Electronic battery feed circuit for telephone systems

Claim 2

An electronic battery feed circuit having tip and ring amplifiers for sourcing and sinking current for respective conductors of a telephone subscriber line, each amplifier having complementary inverting and noninverting input connections, and a feedback circuit extending from signal output connections of said amplifiers to signal input connections thereof, said feedback circuit CHARACTERIZED BY voltage reducing means in an input part of said feedback circuit for reducing voltages coupled thereto from said output connections, a common mode amplifier having an input coupled to receive signals at a low-voltage end of said reducing means and an output coupled to like-type signal inputs of both said ti p amplifier and said ring amplifier, and coupling means, in an output portion of said feedback circuit, for coupling like versions of feedback signals to complementary-type inputs of said tip and ring amplifiers, respectively.

Claim 3

The electronic line feed circuit in accordance with claim 1 in which said voltage reducing means is CHARACTERIZED BY resistive means connected in series between said tip and ring amplifier outputs and an input of said common mode amplifier for reducing feedback voltages by an amount sufficient to permit employment of a substantially lower voltage technology in said common mode amplifier than in said tip and ring amplifiers.

Claim 4

The electronic battery feed circuit in accordance with claim 2 in which said resistive means is CHARACTERIZED BY first and second resistors each connected at one end to a circuit point between an output of one of said tip and ring amplifiers and a corresponding conductor of said line circuit, third and fourth resistors connected in series between ends of said first and second resistors remote from said tip and ring amplifiers, and means for connecting a series circuit point between said th and fourth resistors to said input of said common mode amplifier.

Claim 5

The electronic line feed circuit in accordance with claim 3 CHARACTERIZED IN THAT said feedback circuit includes a metallic signal feedback amplifier, means is connected to said common mode amplifier for establishing said series circuit point as a virtual ground, and means is provided for connecting said remote ends of said first and second resistors to an input of said metallic feedback amplifier.

Claim 6

The electronic line feed circuit in accordance with claim 1 CHARACTERIZED BY means for adjustably regulating a supply voltage, means for supplying an output of said regulating means to said tip and ring amplifiers as operating potential therefor, and means, responsive to changes in signal level in said feedback circuit, for adjusting operation of said regulating means to control the output of said regulating means in a direction and amount corresponding to said changes.

Claim 7

The electronic line feed circuit in accordance with claim 5 CHARACTERIZED BY means, responsive to an output of said regulating means, for supplying a corresponding current input to said common mode amplifier in current combinatorial relation with said signals at said low end of said reducing means.

Claim 8

An electronic battery feed circuit having tip and ring line amplifiers and a feedback circuit from outputs to inputs of said amplifiers, said battery feed circuit CHARACTERIZED BY means for adjustably regulating a supply voltage, means for supplying an output of said regulating means to said tip and ring amplifiers as operating voltage therefor, and means, responsive to changes in signal level in said feedback circuit, for adjusting operation of said regulating means to control said output of said regulating means in a direction tending to track said changes.

Claim 9

An electronic battery feed circuit having tip and ring line amplifiers and a feedback circuit from outputs to inputs of said amplifiers, said battery feed circuit CHARACTERIZED BY means for adjustably regulating a supply voltage, means for supplying an output of said regulating means to said tip and ring amplifiers as operating voltage therefor, and means, responsive to changes in signal level in said feedback circuit, for adjusting operation of said regulating means to control said output of said regulating means in a direction tending to track said changes.

Claim 10

The electronic battery feed circuit in accordance with claim 7 CHARACTERIZED IN THAT said amplifiers have complementary inverting and noninverting input connections, said feedback circuit includes means, responsive to signals in an input of said feedback circuit, for applying corresponding signals to like inputs of said tip and ring amplifiers, means, responsive to an output of said regulating means, are provided for producing a reference signal, and means are provided for increasing or decreasing said corresponding signals depending upon whether said signals at said input of said feedback circuit are larger or smaller than said reference signal.

Claim 11

The electronic battery feed circuit in accordance with claim 7 CHARACTERIZED IN THAT said feedback circuit includes both a metallic signal feedback circuit and a common mode signal feedback circuit, and said adjusting means comprises , means, responsive to said signal level in said metallic feedback circuit, for controlling said output of said regulating means, and means in said common mode signal feedback circuit for fixing the sum of voltages of outputs of said tip and ring line amplifiers to be approximately equal to said regulated supply voltage.

Claim 12

The electronic battery feed circuit in accordance with claim 7 CHARACTERIZED IN THAT said amplifiers have complementary inverting and noninverting input connections, said feedback circuit has separate ground- referenced outputs for metallic signals and for common mode signals, and means are provided in inputs of said amplifiers for connecting said common mode feedback signals through separate resistances at said like inputs of said amplifiers, respectively, and for connecting said metallic feedback signals through separate resistances at unlike inputs of said amplifiers, respectively.

Claim 13

The electronic battery feed circuit in accordance with claim 7 CHARACTERIZED IN THAT said feedback circuit has separate ground- referenced outputs for metallic signals and for common mode signals, said amplifiers each comprises an operational amplifier having complementary inverting and noninverting input connections and resistance means for receiving signals at such input connections from said feedback circuit, and said resistance means is CHARACTERIZED BY a first resistance voltage divider connected for receiving both said metallic and said common mode signals to one input of one of said amplifiers, a second resistance voltage divider connected for receiving said common mode signals to an input, like said one input, of another of said amplifiers, a third resistance voltage divider connected for receiving said metallic signals to an input, unlike said one input, of said another of said amplifiers, all of said voltage dividers have resistances thereof proportioned so that the same Thevenin equivalent network impedance is seen looking back from said one input and said like input of said amplifiers toward said feedback circuit common mode signal output, and so that the same Thevenin equivalent network impedance is seen looking back from said one input and said unlike input of said amplifiers toward said feedback circuit metallic signal output, and resistance means, including said separate resistances, connected to inputs of said amplifiers and proportioned so all like and unlike inputs of said amplifiers see equal resistances to ground.

Claim 14

An electronic battery feed circuit having tip and ring line amplifiers CHARACTERIZED BY means for adjustably regulating a voltage at one rail of a supply having its other rail connected to a predetermined reference voltage point, means for supplying an output of said regulating means at said one rail to said amplifiers, which amplifiers are also connected to said reference rail, and means, responsive to an output of said regulating means, for varying the voltage operating points of said amplifiers to hold said operating points approximately symmetrically spaced with respect to a voltage midway between voltages of said rails.

Claim 15

An electronic battery feed circuit having tip and ring line amplifiers CHARACTERIZED BY means for adjustably regulating a voltage at one rail of a supply having its other rail connected to a predetermined reference voltage point, means for supplying an output of said regulating means at said one rail to said amplifiers, which amplifiers are also connected to said reference rail, and means, responsive to an output of said regulating means, for varying the voltage operating points of said amplifiers to hold said operating points approximately symmetrically spaced with respect to a voltage midway between voltages of said rails.