Supervisory circuit for telephone lines

Claim 2

A supervisory circuit for detecting the condition of a telephone system subscriber line, said line including two line conductors, said supervisory circuit comprising a battery conductor including a battery resistor connected between one of said line conductors and a battery, a ground conductor including a ground resistor connected between the other of said line conductors and ground, a first and a second voltage divider each having an output tap and each having a high impedance with respect to said battery and ground resistors, said first divider being connected between the line conductor side of said battery resistor and ground and said second divider being connected between the line conductor side of said ground resistor and said battery, a biasing resistor connected between the output tap of said second divider and ground for controlling the relative outputs and polarity of said dividers, and amplifying means energized responsive to a difference in output potentials on saId taps for generating an output signal indicative of the condition of said line.

Claim 3

A supervisory circuit for detecting the operative state of a communication line circuit including two line conductors, said supervisory circuit comprising a first and a second voltage divider each having an output tap and each being connected at one end to one and the other of said line conductors, respectively, in parallel relation across said communication line circuit, the other ends of said voltage dividers, being connected together through a source of potential, a first load resistor connected between the said one end of said first voltage divider and the said other end of said second voltage divider, a second load resistor connected between the said one end of said second voltage divider and the said other end of said first voltage divider, a differential amplifier having a pair of inputs connected respectively to the taps of said dividers, and a biasing resistor connected between one of said taps and one side of said source, said amplifier having one output when the voltage difference between said taps is of one predetermined magnitude and polarity and another output when said difference is of another predetermined magnitude and the opposite polarity.

Claim 4

A supervisory circuit for detecting the operative state of a communication line circuit including two line conductors, said supervisory circuit comprising a first and a second voltage divider each having an output tap and each being connected at one end to one and the other of said line conductors, respectively, in parallel relation across said communication line circuit, the other ends of said voltage dividers, being connected together through a source of potential, a first load resistor connected between the said one end of said first voltage divider and the said other end of said second voltage divider, a second load resistor connected between the said one end of said second voltage divider and the said other end of said first voltage divider, a differential amplifier having a pair of inputs connected respectively to the taps of said dividers, and a biasing resistor connected between one of said taps and one side of said source, said amplifier having one output when the voltage difference between said taps is of one predetermined magnitude and polarity and another output when said difference is of another predetermined magnitude and the opposite polarity.

Claim 5

A supervisory circuit for detecting the operative state of a communication line circuit including two line conductors, said supervisory circuit comprising a pair of branches connected at one end to one and the other of said line conductors, respectively, each of said branches serially including a pair of load resistors, a source of potential connected between the other ends of said branches, a first and a second voltage divider each having an output tap and each being connected at one end to one of said branches between the load resistors of a load resistor pair and each being connected at the other end to the opposite branch at opposite sides of said potential source, respectively, a differential amplifier having a pair of inputs connected respectively to the taps of said voltage dividers, and a biasing resistor connected between one of said taps and one side of said source, the sum values of said pairs of load resistors being of a magnitude to offer a high impedance to said line circuit.

Claim 6

A supervisory circuit for detecting the operative state of a communication line circuit including two line conductors, said supervisory circuit comprising a pair of branches connected at one end to one and the other of said line conductors, respectively, each of said branches serially including a pair of load resistors, a source of potential connected between the other ends of said branches, a first and a second voltage divider each having an output tap and each being connected at one end to one of said branches between the load resistors of a load resistor pair and each being connected at the other end to the opposite branch at opposite sides of said potential source, respectively, a differential amplifier having a pair of inputs connected respectively to the taps of said voltage dividers, and a biasing resistor connected between one of said taps and one side of said source, the sum values of said pairs of load resistors being of a magnitude to offer a high impedance to said line circuit.

Claim 7

A supervisory circuit for monitoring a subscriber line loop in a telephone system comprising a first and a second circuit branch each connected at one end to one and the other side of said line loop, respectively, said first branch being cross connected with said second branch by a first voltage divider having an output tap and said second branch being cross connected with said first branch by a second voltage divider also having an output tap, a source of potential connected between the other ends of said first and second circuit branch, a first load resistor serially connected in said first circuit branch between one end of said first voltage divider and one end of said second voltage divider, a second load resistor serially connected in said second circuit branch between the other end of said first voltage divider and the other end of said second voltage divider, a differential amplifier having a pair of inputs connected to said output taps, and a biasing resistor connected between the output tap of said first voltage divider and the one end of said second voltage divider at said first circuit branch.

Claim 8

A supervisory circuit for monitoring a subscriber line loop in a telephone system comprising a first and a second circuit branch each connected at one end to one and the other side of said line loop, respectively, said first branch being cross connected with said second branch by a first voltage divider having an output tap and said second branch being cross connected with said first branch by a second voltage divider also having an output tap, a source of potential connected between the other ends of said first and second circuit branch, a first load resistor serially connected in said first circuit branch between one end of said first voltage divider and one end of said second voltage divider, a second load resistor serially connected in said second circuit branch between the other end of said first voltage divider and the other end of said second voltage divider, a differential amplifier having a pair of inputs connected to said output taps, and a biasing resistor connected between the output tap of said first voltage divider and the one end of said second voltage divider at said first circuit branch.

Claim 9

A supervisory circuit for monitoring a subscriber line loop in a telephone system comprising a first and a second circuit path connected to one and the other side of said line loop, respectively, said first and second circuit path each including a first and a second branch connected at one end to a branching point of the circuit path, said first branch of each of said circuit paths including a voltage divider and said second branch of each of said circuit paths including a load resistor, the first branch of each of said circuit paths being connected at its other end to the other end of the second branch of the other of said circuit paths, a differential amplifier having a pair of inputs connected respectively to output taps of said voltage dividers, a biasing resistor connected between an output tap of a voltage divider of one circuit path and the other end of the second branch of the same circuit path, and a source of potential connected between the other ends of said second branches of said circuit paths.

Claim 10

A supervisory circuit for monitoring a subscriber line loop in a telephone system comprising a first and a second circuit path connected to one and the other side of said line loop, respectively, said first and second circuit path each including a first and a second branch connected at one end to a branching point of the circuit path, said first branch of each of said circuit paths including a voltage divider and said second branch of each of said circuit paths including a load resistor, the first branch of each of said circuit paths being connected at its other end to the other end of the second branch of the other of said circuit paths, a differential amplifier having a pair of inputs connected respectively to output taps of said voltage dividers, a biasing resistor connected between an output tap of a voltage divider of one circuit path and the other end of the second branch of the same circuit path, and a source of potential connected between the other ends of said second branches of said circuit paths.

Claim 11

A supervisory circuit according to claim 5 in which each of said circuit paths also includes a second load resistor connected between said line loop and said branching point, the sum magnitude of the load resistors in each of said circuit paths presenting a high shunt resistance with respect to the alternating-current impedance of said loop.

Claim 12

In a telephone system, in combination, a communication loop having predetermined current conditions, a battery feed circuit comprising a battery conductor connected to one side of said loop including a first feed resistor and terminating in a source of potential and a ground conductor connected to the other side of said loop including a second feed resistor and terminating in ground, a pair of voltage divider circuits connected between said one side of said loop and ground and between said other side of said loop and said source, respectively, and a differential amplifier means having a pair of inputs connected to respective taps of said voltage divider circuits, currents between said source and ground in said first and second voltage divider circuits applying different bias voltages to said inputs to maintain said amplifier means nonconductive in the absence of current in said loop.

Claim 13

In a telephone system, in combination, a communication loop having predetermined current conditions, a battery feed circuit comprising a battery conductor connected to one side of said loop including a first feed resistor and terminating in a source of potential and a ground conductor connected to the other side of said loop including a second feed resistor and terminating in ground, a pair of voltage divider circuits connected between said one side of said loop and ground and between said other side of said loop and said source, respectively, and a differential amplifier means having a pair of inputs connected to respective taps of said voltage divider circuits, currents between said source and ground in said first and second voltage divider circuits applying different bias voltages to said inputs to maintain said amplifier means nonconductive in the absence of current in said loop.

Claim 14

In a telephone system, the combination as claimed in claim 7 also comprising a biasing resistor connected between one of said taps and said ground for biasing said amplifier means in a conductive state in the presence of current in said loop of a predetermined magnitude.

Claim 15

A supervisory circuit for a telephone system comprising a communication loop having predetermined current conditions, a first and a second voltage divider means parallely connected at one end to respective opposite sides of said loop, a differential amplifier having a pair of inputs and an output terminal, said inputs being connected respectively to the taps of said first and second voltage divider means, and means for applying different bias voltages to said inputs for maintaining said amplifier means nonconductive comprising a first circuit including said first voltage divider means and a source of potential connected to said one end of said last-mentioned divider means and a second circuit including said second voltage divider means and said source of potential connected to the other end of said last-mentioned divider means.

Claim 16

A supervisory circuit for a telephone system comprising a communication loop having predetermined current conditions, a first and a second voltage divider means parallely connected at one end to respective opposite sides of said loop, a differential amplifier having a pair of inputs and an output terminal, said inputs being connected respectively to the taps of said first and second voltage divider means, and means for applying different bias voltages to said inputs for maintaining said amplifier means nonconductive comprising a first circuit including said first voltage divider means and a source of potential connected to said one end of said last-mentioned divider means and a second circuit including said second voltage divider means and said source of potential connected to the other end of said last-mentioned divider means.

Claim 17

A supervisory circuit for a telephone system as claimed in claim 9 also comprising a biasing resistor means connected between the tap of said second voltage divider means and the other end of said first voltage divider means for controlling said bias voltage on said inputs responsive to the presence of current of a predetermined magnitude in said loop for causing said amplifier means to generate an output signal on said output terminal.