Impedance responsive voltage booster circuit for telephone systems

Claim 2

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transimission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, booster source means, latchable switching means for connecting said booster source means between the central office battery and the transmission line in series-aiding relationship to the central office battery, means for connecting said latchable switching means to the transmission line and to said booster source means, means for initiating conduction through said switching means when the central office battery is connected to the transmission line with a predetermined polarity, threshold means for establishing a current threshold for latched conduction through said latchable switching means, means for connecting said threshold means to said latchable switching means, means for diverting latching current away from said latchable switching means in accordance with the magnitude of current in the transmission line and means for connecting said diverting means to said latchable switching means.

Claim 3

In a circuit for increasing and decreasing the d-c operating voltage of a cummunications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, booster source means, first switching means for connecting said booster source means between the central office battery and the transmission line in series-aiding relationship to the central office battery, second switching means for bypassing transmission line current around said first switching means, means for connecting said switching means to the transmission line, means for initiating condution through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, means for turning off said first switching means when the transmission line current flowing therethrough drops below a predetermined value and means for connecting said turn off means to said first switching means and to said booster source means.

Claim 4

In a circuit for increasing and decreasing the d-c operating voltage of a cummunications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, booster source means, first switching means for connecting said booster source means between the central office battery and the transmission line in series-aiding relationship to the central office battery, second switching means for bypassing transmission line current around said first switching means, means for connecting said switching means to the transmission line, means for initiating condution through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, means for turning off said first switching means when the transmission line current flowing therethrough drops below a predetermined value and means for connecting said turn off means to said first switching means and to said booster source means.

Claim 5

A voltage booster circuit as set forth in claim 2 including capacitance means, means for connecting said capacitance means to said first switching means and to said booster source means to filter the boost voltage added by the voltage boosting circuitry during the conduction of said first switching means and means for connecting said capacitance means to said second switching means.

Claim 6

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first latchable switching means for controlling the flow of current in a first direction in the transmission line, said first latchable switching means including power circuit means and control circuit means, second switching means for controlling the flow of current in a second direction in the transmission line, said second switching means including power circuit means and control circuit means, means for connecting the power circuit means of said switching means in series with the transmission line, means for energizing the control circuit means of said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means in series with the power circuit means of said first latchable switching means, current threshold means for establishing a current threshold for latched conduction through said first latchable switching means, means for connecting said current threshold means to said first latchable switching means, means for diverting latching current away from said first latchable switching means and means for connecting said latching current diverting means to said first latchable switching means.

Claim 7

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first latchable switching means for controlling the flow of current in a first direction in the transmission line, said first latchable switching means including power circuit means and control circuit means, second switching means for controlling the flow of current in a second direction in the transmission line, said second switching means including power circuit means and control circuit means, means for connecting the power circuit means of said switching means in series with the transmission line, means for energizing the control circuit means of said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means in series with the power circuit means of said first latchable switching means, current threshold means for establishing a current threshold for latched conduction through said first latchable switching means, means for connecting said current threshold means to said first latchable switching means, means for diverting latching current away from said first latchable switching means and means for connecting said latching current diverting means to said first latchable switching means.

Claim 8

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster circuits each having first and second terminal means, each booster circuit including first latchable switching means for controlling the flow of current from the first to the second terminal means thereof and second switching means for controlling the flow of current From the second to the first terminal means thereof, means for connecting said booster circuits in series with the transmission line, means for initiating conduction through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means between the terminal means of respective booster circuits through respective first latchable switching means, threshold means for establishing current thresholds for latched conduction through said first latchable switching means, means for connecting said threshold means to said first latchable switching means, means for diverting latching current away from said first latchable switching means in accordance with the magnitude of current in the transmission line and means for connecting said latching current diverting means to said first latchable switching means and to said booster source means.

Claim 9

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster circuits each having first and second terminal means, each booster circuit including first latchable switching means for controlling the flow of current from the first to the second terminal means thereof and second switching means for controlling the flow of current From the second to the first terminal means thereof, means for connecting said booster circuits in series with the transmission line, means for initiating conduction through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means between the terminal means of respective booster circuits through respective first latchable switching means, threshold means for establishing current thresholds for latched conduction through said first latchable switching means, means for connecting said threshold means to said first latchable switching means, means for diverting latching current away from said first latchable switching means in accordance with the magnitude of current in the transmission line and means for connecting said latching current diverting means to said first latchable switching means and to said booster source means.

Claim 10

A voltage boosting circuit as set forth in claim 5 including capacitance means, means for connecting said capacitance means between the terminal means of respective booster circuits, and means for connecting said capacitance means to respective second switching means.

Claim 11

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magntidue of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first and second terminal means for disposition in series with one conductor of a transmission line, a first latchable switching network for controlling the flow of transmission line current from said first to said second terminal means, said first latchable switching network including triggering means having a power circuit and a control circuit and latching means having a power circuit and a control circuit, a second switching network for controlling the flow of transmission line current from said second to said first terminal means, means for connecting the power circuit of said triggering means between the said first and second terminal means through the control circuit of said latching means, means for connecting the control circuit of said triggering means between said first and second terminal means through the power circuit of said latching means, a booster source, means for connecting said booster source between said terminal means through said first latchable switching network, means for initiating conducting through said first or second switching networks when the central office battery is connected to the transmission line with respective first or second polarities, current threshold means for establishing a current threshold for conduction through the control circuit of said latching means, means for connecting said current threshold means across the control circuit of said latching means, means for diverting current away from the control circuit of said triggering means in accordance with the magnitude of current in the transmission line and means for connecting said booster source, said current diverting means and the power circuit of said latching means in a closed circuit path.

Claim 12

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magntidue of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first and second terminal means for disposition in series with one conductor of a transmission line, a first latchable switching network for controlling the flow of transmission line current from said first to said second terminal means, said first latchable switching network including triggering means having a power circuit and a control circuit and latching means having a power circuit and a control circuit, a second switching network for controlling the flow of transmission line current from said second to said first terminal means, means for connecting the power circuit of said triggering means between the said first and second terminal means through the control circuit of said latching means, means for connecting the control circuit of said triggering means between said first and second terminal means through the power circuit of said latching means, a booster source, means for connecting said booster source between said terminal means through said first latchable switching network, means for initiating conducting through said first or second switching networks when the central office battery is connected to the transmission line with respective first or second polarities, current threshold means for establishing a current threshold for conduction through the control circuit of said latching means, means for connecting said current threshold means across the control circuit of said latching means, means for diverting current away from the control circuit of said triggering means in accordance with the magnitude of current in the transmission line and means for connecting said booster source, said current diverting means and the power circuit of said latching means in a closed circuit path.

Claim 13

A voltage boosting circuit as set forth in claim 7 including capacitance means, means for connecting said capacitance means between said first and second terminal means and means for connecting said capacitance means to said second switching network.

Claim 14

A voltage booster circuit as set forth in claim 7 in which said means for connecting said central office battery to said switching networks to control the conduction thereof comprises trigger current conducting means and means for connecting said trigger current conducting means between said first and second terminal means.

Claim 15

A voltage boosting circuit as set forth in claim 7 in whicH said means for connecting said central office battery to said switching networks to control the conduction thereof comprises trigger current conducting means and means for connecting said trigger current conducting means between the transmission line conductors.

Claim 16

A voltage boosting circuit as set forth in claim 7 in which said latching means is a thyristor and in which said triggering means is an NPN transistor.

Claim 17

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster circuits each having first and second terminal means, each booster circuit including a first latchable switching network for initiating and terminating the flow of current from the first to the second terminal means thereof and a second switching network for initiating the flow of current from the second to the first terminal means thereof, means for connecting the second terminal means of each booster circuit to a respective central office terminal, means for connecting the first terminal means of each booster circuit to a respective subscriber line terminal, means for initiating conduction through said first and second switching networks when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means between said first and second terminal means through respective first latchable switching networks, current threshold means for establishing a current threshold for latched conduction through said first latchable switching means, means for connecting said current threshold means to said first latchable switching networks, means for diverting latching current away from said first latchable switching networks in accordance with the magnitude of current in the subscriber line and means for connecting said latching current diverting means between said first latchable switching networks and said booster source means.

Claim 18

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster circuits each having first and second terminal means, each booster circuit including a first latchable switching network for initiating and terminating the flow of current from the first to the second terminal means thereof and a second switching network for initiating the flow of current from the second to the first terminal means thereof, means for connecting the second terminal means of each booster circuit to a respective central office terminal, means for connecting the first terminal means of each booster circuit to a respective subscriber line terminal, means for initiating conduction through said first and second switching networks when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means between said first and second terminal means through respective first latchable switching networks, current threshold means for establishing a current threshold for latched conduction through said first latchable switching means, means for connecting said current threshold means to said first latchable switching networks, means for diverting latching current away from said first latchable switching networks in accordance with the magnitude of current in the subscriber line and means for connecting said latching current diverting means between said first latchable switching networks and said booster source means.

Claim 19

A voltage boosting circuit as set forth in claim 12 including capacitance means, means for connecting said capacitance means between the first and second terminal means of respective booster circuits and means for connecting said capacitance means to respective second switching networks.

Claim 20

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster circuits each having first and second terminal means, each booster circuit including a first latchable switching network for initiating and terminating flow of current from the first to the second terminal means thereof and a second switching network for initiating the flow of current from the second to the first terminal means thereof, means for connecting the second terminal means of one booster circuit to one central office terminal, means for connecting the second terminal means of another booster circuit to one subscriber line terminal, means for connecting the first terminal means of said one booster circuit to the first terminal mpans of said another booster circuit, booster source means, means for connecting said booster source means between said connected first terminal means and said first latchable switching networks, current threshold means for establishing a current threshold for latched conduction through said first latchable switching networks, means for connecting said threshold means to said first latchable switchIng networks, means for diverting latching current away from said first latchable switching networks and means for connecting said latching current diverting means to said first latchable switching networks and to said booster source means.

Claim 21

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster circuits each having first and second terminal means, each booster circuit including a first latchable switching network for initiating and terminating flow of current from the first to the second terminal means thereof and a second switching network for initiating the flow of current from the second to the first terminal means thereof, means for connecting the second terminal means of one booster circuit to one central office terminal, means for connecting the second terminal means of another booster circuit to one subscriber line terminal, means for connecting the first terminal means of said one booster circuit to the first terminal mpans of said another booster circuit, booster source means, means for connecting said booster source means between said connected first terminal means and said first latchable switching networks, current threshold means for establishing a current threshold for latched conduction through said first latchable switching networks, means for connecting said threshold means to said first latchable switchIng networks, means for diverting latching current away from said first latchable switching networks and means for connecting said latching current diverting means to said first latchable switching networks and to said booster source means.

Claim 22

A voltage boosting circuit as set forth in claim 14 including capacitance means, means for connecting said capacitance means between the first and second terminal means of respective booster circuits and means for connecting said capacitance means to respective second switching networks.

Claim 23

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first and second terminal means for dispostion in series with a transmission line, first latchable switching means for initiating and terminating the flow of current in a first direction in the transmission line, said first latchable switching means including power circuit means and control circuit means, second switching means for initiating the flow of current in a second direction in the transmission line, said second switching means including power circuit means and control circuit means, means for connecting the power circuit means of said switching means between said first and second terminal means, means for energizing the control circuit means of or first and second switching means when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means between said terminal means through the power circuit means of said first latchable switching means, current threshold means for establishing a current threshold for latching conduction through said first latchable switching means, means for connecting said current threshold means to said first latchable switching means, means for diverting latching current away from the power circuit means of said first latchable switching means and means for connecting said latching current diverting means to said first latchable switching means and to said booster source means.

Claim 24

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first and second terminal means for dispostion in series with a transmission line, first latchable switching means for initiating and terminating the flow of current in a first direction in the transmission line, said first latchable switching means including power circuit means and control circuit means, second switching means for initiating the flow of current in a second direction in the transmission line, said second switching means including power circuit means and control circuit means, means for connecting the power circuit means of said switching means between said first and second terminal means, means for energizing the control circuit means of or first and second switching means when the central office battery is connected to the transmission line with respective first or second polarities, booster source means, means for connecting said booster source means between said terminal means through the power circuit means of said first latchable switching means, current threshold means for establishing a current threshold for latching conduction through said first latchable switching means, means for connecting said current threshold means to said first latchable switching means, means for diverting latching current away from the power circuit means of said first latchable switching means and means for connecting said latching current diverting means to said first latchable switching means and to said booster source means.

Claim 25

A voltage boosting circuit as set forth in claim 16 including capacitance means, means for connecting said capacitance means to said booster source means through the power circuit means of said first latchable switching means, means for connecting said capacitance means to the control circuit means of said second switching means and means for connecting said capacitance means across the power circuit means of said second switching means.

Claim 26

A voltage boosting circuit as set forth in claim 16 in which said means for connecting the central office battery to the control circuit means of said switching means includes trigger current conducting means and means for connecting said trigger current conducting means between said first and second terminal means through the control circuit means of said switching means.

Claim 27

A voltage boosting circuit as set forth in claim 16 in which said means for connecting the central office battery to the control circuit means of said switching means includes trigger current conducting means and means for connecting said trigger current conducting means across the transmission line through the control circuit means of said switching means.

Claim 28

A voltage boosting circuit as set forth in claim 16 in which each of said booster source means comprises an a-c to d-c converter having an output voltage which decreases as the current flowing therethrough increases.

Claim 29

In a circuit for increasing and decreasing the d-c operating voltage of a communicaTions transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said trAnsmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first and second terminal means for disposition between a central office battery and a transmission line, first switching means for controlling the flow of current from said first to said second terminal means, second switching means for controlling the flow of current from said second to said first terminal means, booster source means, means for connecting said booster source means between said terminal means through said first switching means, means for initiating conduction through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, said first switching means including: triggering means having a power circuit and a control circuit, latching means having a power circuit and a control circuit, said latching means comprising means for controlling the flow of latching the magnitude of current through the control circuit of said triggering means in accordance with the magnitude of the transmission line current entering said first terminal means, said triggering means comprising means for controlling the flow of current through the control circuit of said latching means in accordance with the magnitude of the latching current flowing through the control circuit of said triggering means, threshold means for setting a current threshold for conduction through said latching means, means for connecting said threshold means to said latching means, means for diverting latching current away from the control circuit of said triggering means in accordance with current in the transmission line, means for connecting said diverting means to the control circuit of said triggering means and means for connecting said latching means and said triggering means to each other.

Claim 30

In a circuit for increasing and decreasing the d-c operating voltage of a communicaTions transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said trAnsmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, first and second terminal means for disposition between a central office battery and a transmission line, first switching means for controlling the flow of current from said first to said second terminal means, second switching means for controlling the flow of current from said second to said first terminal means, booster source means, means for connecting said booster source means between said terminal means through said first switching means, means for initiating conduction through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, said first switching means including: triggering means having a power circuit and a control circuit, latching means having a power circuit and a control circuit, said latching means comprising means for controlling the flow of latching the magnitude of current through the control circuit of said triggering means in accordance with the magnitude of the transmission line current entering said first terminal means, said triggering means comprising means for controlling the flow of current through the control circuit of said latching means in accordance with the magnitude of the latching current flowing through the control circuit of said triggering means, threshold means for setting a current threshold for conduction through said latching means, means for connecting said threshold means to said latching means, means for diverting latching current away from the control circuit of said triggering means in accordance with current in the transmission line, means for connecting said diverting means to the control circuit of said triggering means and means for connecting said latching means and said triggering means to each other.

Claim 31

A voltage boosting circuit as set forth in claim 21 including capacitance means, means for connecting said booster source means to said capacitance means through said first switching means, means for connecting said capacitance means across said second switching means and means for connecting said capacitance means to said second swithcing means to initiate conduction through said second switching means on switching off of said first switching means.

Claim 32

In a circuit for increasing and descreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, bridge circuit means having a-c terminal means and d-c terminal means, means for connecting said a-c terminal means in series with a transmission line, booster source means, means for connecting said booster source means across said d-c terminal means, said bridge circuit means including a switching network in each arm, means for connecting the central office battery to said switching networks to initiate conduction through the switching networks in one pair of arms of said bridge circuit means for one polarity of the central office battery and to initiate conduction through the switching networks in a different pair of arms of said bridge means for the other polarity of the central office battery, current threshold means for setting a current threshold for conduction through at least one of said switching networks, means for connecting said current threshold means to at least one of said switching networks, current diverting means for controling the magnitude of current flow through the current threshold means of those switching networks having current threshold means in accordance with the magnitude of current in the transmission line and means for connecting said current controlling means to said booster source means and to said at lEast one of said switching networks.

Claim 33

In a circuit for increasing and descreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, bridge circuit means having a-c terminal means and d-c terminal means, means for connecting said a-c terminal means in series with a transmission line, booster source means, means for connecting said booster source means across said d-c terminal means, said bridge circuit means including a switching network in each arm, means for connecting the central office battery to said switching networks to initiate conduction through the switching networks in one pair of arms of said bridge circuit means for one polarity of the central office battery and to initiate conduction through the switching networks in a different pair of arms of said bridge means for the other polarity of the central office battery, current threshold means for setting a current threshold for conduction through at least one of said switching networks, means for connecting said current threshold means to at least one of said switching networks, current diverting means for controling the magnitude of current flow through the current threshold means of those switching networks having current threshold means in accordance with the magnitude of current in the transmission line and means for connecting said current controlling means to said booster source means and to said at lEast one of said switching networks.

Claim 34

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of bridge circuit means each having a-c terminal means and d-c terminal means, means for connecting the a-c terminal means of one of said bridge circuit means in series with one side of a transmission line, means for connecting the a-c terminal means of another of said bridge circuit means in series with the other side of a transmission line, booster source means, means for connecting said booster source means across the d-c terminal means of respective bridge circuit means, each of said bridge circuit means including a switching network in each arm means for connecting the central office battery to said bridge circuit means to inititate conduction through the switching networks in one pair of arms for one polarity of the central office battery and to initiate conduction through the switching networks in a different pair of arms for the other polarity of the central office battery, current threshold means for setting a current threshold for conduction through at least one of the switching networks in each of said bridge circuit means, means for connecting said current threshold means to at least one of the switching networks in each of said bridge circuit means, current diverting means for controlling the magnitude of current flow through the current threshold means of those switching networks having current threshold means in accordance with the magnitude of current in the transmission line and means for connecting said current diverting means to said booster source means and to those switching networks having current threshold means.

Claim 35

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of bridge circuit means each having a-c terminal means and d-c terminal means, means for connecting the a-c terminal means of one of said bridge circuit means in series with one side of a transmission line, means for connecting the a-c terminal means of another of said bridge circuit means in series with the other side of a transmission line, booster source means, means for connecting said booster source means across the d-c terminal means of respective bridge circuit means, each of said bridge circuit means including a switching network in each arm means for connecting the central office battery to said bridge circuit means to inititate conduction through the switching networks in one pair of arms for one polarity of the central office battery and to initiate conduction through the switching networks in a different pair of arms for the other polarity of the central office battery, current threshold means for setting a current threshold for conduction through at least one of the switching networks in each of said bridge circuit means, means for connecting said current threshold means to at least one of the switching networks in each of said bridge circuit means, current diverting means for controlling the magnitude of current flow through the current threshold means of those switching networks having current threshold means in accordance with the magnitude of current in the transmission line and means for connecting said current diverting means to said booster source means and to those switching networks having current threshold means.

Claim 36

A voltage boosting circuit as set forth in claim 24 in which the current threshold for conduction through one of said bridge circuit means is different from the current threshold for conduction through the other of said bridge circuit means.

Claim 37

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster sources, first switching means for connecting one of said booster sources in series-aiding relationship to the central office battery when current in the transmission line flows in one direction, second switching means for connecting another of said booster sources in series-aiding relationship to the central office battery when current in the transmission line flows in the other direction, means for connecting said switching means in series with the transmission line, means for connecting said switching means to said booster sources, means for initiating conduction through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, means for turning off one of said switching means in accordance with the magnitude of current in the transmission line and means for connecting said turn-off means to said one switching means.

Claim 38

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, a plurality of booster sources, first switching means for connecting one of said booster sources in series-aiding relationship to the central office battery when current in the transmission line flows in one direction, second switching means for connecting another of said booster sources in series-aiding relationship to the central office battery when current in the transmission line flows in the other direction, means for connecting said switching means in series with the transmission line, means for connecting said switching means to said booster sources, means for initiating conduction through said first or second switching means when the central office battery is connected to the transmission line with respective first or second polarities, means for turning off one of said switching means in accordance with the magnitude of current in the transmission line and means for connecting said turn-off means to said one switching means.

Claim 39

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, booster source means, latchable switching means for connecting saId booster source means in series-aiding relationship to the central office battery, means for connecting said latchable switching means in series with the transmission line, means for connecting said latchable switching means in series with said booster source means, means for initiating conduction through said switching means when the central office battery is connected to the transmission line with a predetermined polarity, current responsive means for initiating latched conduction through said latchable switching means when the current in the transmission line rises above a preselected value greater than the leakage current value of the transmission line and for terminating such latched conduction when the current in the transmission line drops below said preselected value, and means for connecting said current responsive means to said latchable switching means.

Claim 40

In a circuit for increasing and decreasing the d-c operating voltage of a communications transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system, to receive a substantially fixed d-c operating voltage, in combination, booster source means, latchable switching means for connecting saId booster source means in series-aiding relationship to the central office battery, means for connecting said latchable switching means in series with the transmission line, means for connecting said latchable switching means in series with said booster source means, means for initiating conduction through said switching means when the central office battery is connected to the transmission line with a predetermined polarity, current responsive means for initiating latched conduction through said latchable switching means when the current in the transmission line rises above a preselected value greater than the leakage current value of the transmission line and for terminating such latched conduction when the current in the transmission line drops below said preselected value, and means for connecting said current responsive means to said latchable switching means.

Claim 41

In a circuit for increasing and decreasing the d-c operating voltage of a communcations transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system to receive a substantially fixed d-c operating voltage, in combination, booster source means, latchable switching means for connecting said booster source means in series-aiding relationship to the central office battery, means for connecting said latchable switching means in series with the transmission line and in series with said booster source means, first means for establishing latched conduction through said switching means when the central office battery is connected to the transmission line with a predetermined polarity and the transmission line current exceeds a preselected value greater than the leakage current of the transmission line, second means for terminating latched conduction through said switching means when the current in the transmission line drops below said preselected value, and means for connecting said first and second means to said switching means and to the transmission line.

Claim 42

In a circuit for increasing and decreasing the d-c operating voltage of a communcations transmission line in a telephone system or the like in accordance with the magnitude of current flow through the transmission line, said transmission line being connected to a central office battery of the telephone system to receive a substantially fixed d-c operating voltage, in combination, booster source means, latchable switching means for connecting said booster source means in series-aiding relationship to the central office battery, means for connecting said latchable switching means in series with the transmission line and in series with said booster source means, first means for establishing latched conduction through said switching means when the central office battery is connected to the transmission line with a predetermined polarity and the transmission line current exceeds a preselected value greater than the leakage current of the transmission line, second means for terminating latched conduction through said switching means when the current in the transmission line drops below said preselected value, and means for connecting said first and second means to said switching means and to the transmission line.