Voltage booster circuit having test-through characteristics

Claim 2

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, means for increasing the conduction through said variable conducting means as the current through said line current indicating means increases above a predetermined value, threshold means for preventing conduction through said variable conducting means when the current through said line current indicating means is less than said predetermined value, timedelay means for introducing a time-delay between changes in the current through said current indicating means and resultant changes in the conduction of said variable conducting means and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 3

A voltage booster circuit as set forth in claim 1 including ground terminal means, voltage responsive means for overriding said time-delay means when the voltage between said ground terminal means and said one conductor of the subscriber line assumes a predetermined polarity and means for connecting said voltage responsive means to said ground terminal means and to said one conductor of the subscriber line.

Claim 4

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, first and second boost voltage supply means, first and second variable conducting means, means for connecting respective boost voltage supply means between said terminal means through respective variable conducting means, means for increasing the conduction through said first or second variable conducting means, respectively, as the current through said line current indicating means increases above respective positive or negative predetermined values, threshold means for preventing conduction through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values, time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 5

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, first and second boost voltage supply means, first and second variable conducting means, means for connecting respective boost voltage supply means between said terminal means through respective variable conducting means, means for increasing the conduction through said first or second variable conducting means, respectively, as the current through said line current indicating means increases above respective positive or negative predetermined values, threshold means for preventing conduction through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values, time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 6

A voltage booster circuit as set forth in claim 3 including ground terminal means, voltage responsive means for overriding said time-delay means when the voltage between said ground terminal means and said one conductor of the subscriber line assumes a predetermined polarity and means for connecting said voltage responsive means to said ground terminal means and to said one conductor of the subscriber line.

Claim 7

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the central office and subscriber terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: first and second boost voltage supply means, first and second variable conducting means, means for connecting respective boost voltage supply means between said terminal means through respective variable conducting means, line current indicating means, means for connecting said indicating means to the subscriber line, means for increasing the conduction through said first or second variable conducting means, respectively, as the current through said line current indicating means increases above respective positive or negative predetermined values, threshold means for preventing conduction through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values, time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 8

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the central office and subscriber terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: first and second boost voltage supply means, first and second variable conducting means, means for connecting respective boost voltage supply means between said terminal means through respective variable conducting means, line current indicating means, means for connecting said indicating means to the subscriber line, means for increasing the conduction through said first or second variable conducting means, respectively, as the current through said line current indicating means increases above respective positive or negative predetermined values, threshold means for preventing conduction through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values, time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 9

A voltage booster circuit as set forth in claim 5 in which each voltage booster network includes ground terminal means, voltage responsive means for overriding said time-delay means when the voltage between said ground terminal means and the respective one of the conductors of the subscriber line assumes a predetermined polarity and means for connecting said voltage responsive means to said ground terminal means and to the respective one of the conductors of the subscriber line.

Claim 10

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means fOr connecting the central office and subscriber terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: line current indicating means, means for connecting said line current indicating means to the subscriber line, a boost voltage supply, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means when current flows through said line current indicating means in one direction, means for conducting subscriber line current between said terminal means when current flows through said line current indicating means in the other direction, means for increasing the conduction through said variable conducting means in accordance with increases in the current through said line current indicating means in said one direction when the latter current is greater than a predetermined value, threshold means for preventing conduction through said variable conducting means when the instantaneous value of the flow of current through said line current indicating means in said one direction is less than said predetermined value, time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said current indicating means and resultant changes in the conduction of said variable conducting means and means for conducting current between said line terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 11

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means fOr connecting the central office and subscriber terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: line current indicating means, means for connecting said line current indicating means to the subscriber line, a boost voltage supply, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means when current flows through said line current indicating means in one direction, means for conducting subscriber line current between said terminal means when current flows through said line current indicating means in the other direction, means for increasing the conduction through said variable conducting means in accordance with increases in the current through said line current indicating means in said one direction when the latter current is greater than a predetermined value, threshold means for preventing conduction through said variable conducting means when the instantaneous value of the flow of current through said line current indicating means in said one direction is less than said predetermined value, time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said current indicating means and resultant changes in the conduction of said variable conducting means and means for conducting current between said line terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 12

A voltage booster circuit as set forth in claim 7 in which each voltage booster network includes ground terminal means, voltage responsive means for overriding said time-delay means when the voltage between said ground terminal means and the respective one of the conductors of the subscriber line assumes a predetermined polarity and means for connecting said voltage responsive means to said ground terminal means and to the respective one of the conductors of the subscriber line.

Claim 13

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, control means for decreasing the voltage across said variable conducting means in accordance with increases in the current through said line current indicating means when the latter current is greater than a first predetermined value and for maintaining a substantially fixed voltage across said variable conducting means when the current through said line current indicating means exceeds a second predetermined value, means for connecting said control means to said line current indicating means and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said first predetermined value.

Claim 14

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, control means for decreasing the voltage across said variable conducting means in accordance with increases in the current through said line current indicating means when the latter current is greater than a first predetermined value and for maintaining a substantially fixed voltage across said variable conducting means when the current through said line current indicating means exceeds a second predetermined value, means for connecting said control means to said line current indicating means and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said first predetermined value.

Claim 15

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, means for establishing a first, predetermined value of positive resistance between said terminal means when the current through the subscriber line is between zero and a first positive value, means for establishing a first, predetermined value of negative resistance between said line terminal means when the current through the subscriber line is between said first positive value and a second positive value, means for establishing a predetermined positive voltage betWeen said terminal means when the current through the subscriber line is greater than said second positive value, means for establishing a second, predetermined value of positive resistance between said terminal means when the current through the subscriber line is between zero and a first negative value, means for establishing a second, predetermined value of negative resistance between said terminal means when the current through the subscriber line is between said first negative value and a second negative value and means for establishing a predetermined negative voltage between said terminal means when the current through the subscriber line is greater then said second negative value.

Claim 16

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, means for establishing a first, predetermined value of positive resistance between said terminal means when the current through the subscriber line is between zero and a first positive value, means for establishing a first, predetermined value of negative resistance between said line terminal means when the current through the subscriber line is between said first positive value and a second positive value, means for establishing a predetermined positive voltage betWeen said terminal means when the current through the subscriber line is greater than said second positive value, means for establishing a second, predetermined value of positive resistance between said terminal means when the current through the subscriber line is between zero and a first negative value, means for establishing a second, predetermined value of negative resistance between said terminal means when the current through the subscriber line is between said first negative value and a second negative value and means for establishing a predetermined negative voltage between said terminal means when the current through the subscriber line is greater then said second negative value.

Claim 17

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, means for establishing a predetermined positive resistance between said terminal means when the current through the subscriber line in one direction is between zero and a first value, means for establishing a predetermined negative resistance between said terminal means when the current through the subscriber line in said one direction is between said first value and a second value, means for establishing a predetermined positive voltage between said terminal means when the current through the subscriber line in said one direction is greater than said second value, and means for establishing a second predetermined positive resistance between said terminal means when the current through the subscriber line flows in the other direction.

Claim 18

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, means for establishing a predetermined positive resistance between said terminal means when the current through the subscriber line in one direction is between zero and a first value, means for establishing a predetermined negative resistance between said terminal means when the current through the subscriber line in said one direction is between said first value and a second value, means for establishing a predetermined positive voltage between said terminal means when the current through the subscriber line in said one direction is greater than said second value, and means for establishing a second predetermined positive resistance between said terminal means when the current through the subscriber line flows in the other direction.

Claim 19

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, amplifying means having input means and output means, means for connecting said boost voltage supply means between said terminal means through the output means of said amplifying means, means for connecting the input means of said amplifying means to said line current indicating means, said amplifying means serving to increase the voltage between said terminal means in accordance with increases in the current through said line current indicating means when the latter current is greater than a predetermined value, threshold means for preventing conduction through said output means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 20

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, amplifying means having input means and output means, means for connecting said boost voltage supply means between said terminal means through the output means of said amplifying means, means for connecting the input means of said amplifying means to said line current indicating means, said amplifying means serving to increase the voltage between said terminal means in accordance with increases in the current through said line current indicating means when the latter current is greater than a predetermined value, threshold means for preventing conduction through said output means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 21

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, positive and negative boost voltage supply means, amplifying means having input means and first and second output means, means for connecting said positive and negative boost voltage supply means between said terminal means through respective first and second output means of said amplifying means, means for connecting the input means of said amplifying means to said line current indicating means, said amplifying means serving to increase the flow of current through said first or second output means, respectively, in accordance with increases in the current through said line current indicating means when the latter current is greater than respective positive or negative pRedetermined values, threshold means for preventing current flow through said first and second output means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 22

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, positive and negative boost voltage supply means, amplifying means having input means and first and second output means, means for connecting said positive and negative boost voltage supply means between said terminal means through respective first and second output means of said amplifying means, means for connecting the input means of said amplifying means to said line current indicating means, said amplifying means serving to increase the flow of current through said first or second output means, respectively, in accordance with increases in the current through said line current indicating means when the latter current is greater than respective positive or negative pRedetermined values, threshold means for preventing current flow through said first and second output means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 23

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the central office and subscriber terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: positive and negative boost voltage supply means, amplifying means having input means and first and second output means, means for connecting said positive and negative boost voltage supply means between said terminal means through respective first and second output means of said amplifying means, line current indicating means, means for connecting said line current indicating means to the subscriber line, said amplifying means serving to increase the flow of current through said first or second output means, respectively, in accordance with increases in the current through said line current indicating means when the latter current increases above respective positive or negative predetermined values, means for connecting the input means of said amplifying means to said line current indicating means, threshold means for preventing current flow through said first and second output means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 24

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the central office and subscriber terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: positive and negative boost voltage supply means, amplifying means having input means and first and second output means, means for connecting said positive and negative boost voltage supply means between said terminal means through respective first and second output means of said amplifying means, line current indicating means, means for connecting said line current indicating means to the subscriber line, said amplifying means serving to increase the flow of current through said first or second output means, respectively, in accordance with increases in the current through said line current indicating means when the latter current increases above respective positive or negative predetermined values, means for connecting the input means of said amplifying means to said line current indicating means, threshold means for preventing current flow through said first and second output means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 25

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: line current indicating means, means for connecting said line current indicating means to the subscriber line, a boost voltage supply, amplifying means having input means and output means, means for connecting said boost voltage supply between said terminal means through the output means of said amplifying means, said amplifying means serving to increase the flow of current through said output means in accordance with increases in the flow of current through said line current indicating means in one direction when the latter current is greater than a predetermined value, means for conducting current between said terminal means when current flows through said line current indicating means in the other direction, means for connecting the input means of said amplifying means to said line current indicating means, threshold means for preventing current flow through said output means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 26

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: line current indicating means, means for connecting said line current indicating means to the subscriber line, a boost voltage supply, amplifying means having input means and output means, means for connecting said boost voltage supply between said terminal means through the output means of said amplifying means, said amplifying means serving to increase the flow of current through said output means in accordance with increases in the flow of current through said line current indicating means in one direction when the latter current is greater than a predetermined value, means for conducting current between said terminal means when current flows through said line current indicating means in the other direction, means for connecting the input means of said amplifying means to said line current indicating means, threshold means for preventing current flow through said output means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 27

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting meAns, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, amplifying means for increasing the flow of current through said variable conducting means as the current through said line current indicating means increases above a predetermined value, said amplifying means having input means and output means, means for connecting the output means of said amplifying means to said varible conducting means, means for connecting the input means of said amplifying means to said line current indicating means, threshold means for preventing current from flowing through said variable conducting means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 28

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting meAns, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, amplifying means for increasing the flow of current through said variable conducting means as the current through said line current indicating means increases above a predetermined value, said amplifying means having input means and output means, means for connecting the output means of said amplifying means to said varible conducting means, means for connecting the input means of said amplifying means to said line current indicating means, threshold means for preventing current from flowing through said variable conducting means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 29

A voltage booster circuit as set forth in claim 16 in which said variable conducting means includes a control transistor having a power circuit and a control circuit, a line current carrying transistor having a power circuit and a control circuit, means for connecting the power circuit of said line current carrying transistor to said terminal means and said boost voltage supply means and means for connecting the power circuit of said control transistor to the control circuit of said line current carrying transistor.

Claim 30

A voltage booster circuit as set forth in claim 17 including resistance means and means for connecting said resistance means to said boost voltage supply means and to said transistors.

Claim 31

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, first and second boost voltage supply means, first and second variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, amplifying means for increasing the flow of current through said first or second variable conducting means, respectively, as the current through said line curent indicating means increases above respective positive or negative predetermined values, means for connecting said amplifying means to said line current indicating means and to said variable conducting means, threshold means for preventing current flow through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 32

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, first and second boost voltage supply means, first and second variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, amplifying means for increasing the flow of current through said first or second variable conducting means, respectively, as the current through said line curent indicating means increases above respective positive or negative predetermined values, means for connecting said amplifying means to said line current indicating means and to said variable conducting means, threshold means for preventing current flow through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 33

A voltage booster circuit as set forth in claim 19 in which each variable conducting means includes a control transistor having a power circuit and a control circuit, a line current carrying transistor having a power circuit and a control circuit, means for connecting the power circuit of said line current carrying transistor to said terminal means and said boost voltage supply means and means for connecting the power circuit of said control transistor to the control circuit of said line current carrying transistor.

Claim 34

A voltage booster circuit as set forth in claim 20 including resistance means and means for connecting said resistance means to said boost voltage supply means and to said transistors.

Claim 35

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the terminal means of each booster nEtwork in series with a respective conductor of a subscriber line, each voltage booster network including: first and second boost voltage supply means, first and second variable conducting means, means for connecting said boost voltage supply means between said terminal means through respective variable conducting means, line current indicating means, means for connecting said line current indicating means to the subscriber line, amplifying means for increasing the flow of current through said first or second variable conducting means, respectively, as the current through said line current indicating means increases above respective positive or negative predetermined values, means for connecting said amplifying means to said line current indicating means and to said variable conducting means, threshold means for preventing current flow through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 36

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the terminal means of each booster nEtwork in series with a respective conductor of a subscriber line, each voltage booster network including: first and second boost voltage supply means, first and second variable conducting means, means for connecting said boost voltage supply means between said terminal means through respective variable conducting means, line current indicating means, means for connecting said line current indicating means to the subscriber line, amplifying means for increasing the flow of current through said first or second variable conducting means, respectively, as the current through said line current indicating means increases above respective positive or negative predetermined values, means for connecting said amplifying means to said line current indicating means and to said variable conducting means, threshold means for preventing current flow through said first and second variable conducting means when the current through said line current indicating means is between said positive and negative predetermined values and means for conducting current between said terminal means when the flow of current through said line current indicating means is between said positive and negative predetermined values.

Claim 37

A voltage boosting circuit as set forth in claim 22 in which the variable conducting means of each booster network includes a control transistor having a power circuit and a control circuit, a line current carrying transistor having a power circuit and a control circuit, means for connecting the power circuit of said line current carrying transistor to said terminal means and said boost voltage supply means, and means for connecting the power circuit of said control transistor to the control circuit of said line current carrying transistor.

Claim 38

A voltage booster circuit as set forth in claim 23 in which each booster network includes resistance means and means for connecting said resistance means to said boost voltage supply means and to said transistors.

Claim 39

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: line current indicating means, means for connecting said line current indicating means to the subscriber line, a boost voltage supply, variable conducting means, means for connecting said boost voltage supply between said terminal means through said variable conducting means when current flows through said line current indicating means in one direction, means for conducting current between said terminal means when current flows through said line current indicating means in the other direction, amplifying means for increasing the flow of current through said variable conducting means in accordance with increases in the current through said line current indicating means in said one direction when the latter current is greater than a predetermined value, means for connecting said amplifying means to said line current indicating means and to said variable conducting means, threshold means for preventing current flow through said variable conducting means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 40

A voltage booster circuit having a test-through characteristic, said voltage booster circuit including, in combination, a plurality of voltage booster networks each having central office terminal means and subscriber terminal means, means for connecting the terminal means of each booster network in series with a respective conductor of a subscriber line, each voltage booster network including: line current indicating means, means for connecting said line current indicating means to the subscriber line, a boost voltage supply, variable conducting means, means for connecting said boost voltage supply between said terminal means through said variable conducting means when current flows through said line current indicating means in one direction, means for conducting current between said terminal means when current flows through said line current indicating means in the other direction, amplifying means for increasing the flow of current through said variable conducting means in accordance with increases in the current through said line current indicating means in said one direction when the latter current is greater than a predetermined value, means for connecting said amplifying means to said line current indicating means and to said variable conducting means, threshold means for preventing current flow through said variable conducting means when the current through said line current indicating means is less than said predetermined value and means for conducting current between said terminal means when the flow of current through said line current indicating means is less than said predetermined value.

Claim 41

A voltage boosting circuit as set forth in claim 25 in which the variable conducting means of each booster network includes a control transistor having a power circuit and a control circuit, a line current carrying transistor having a power circuit and a control circuit, means for connecting the power circuit of said line current carrying transistor to said terminal means and said boost voltage supply and means for cOnnecting the power circuit of said control transistor to the control circuit of said line current carrying transistor.

Claim 42

A voltage boosting circuit as set forth in claim 26 in which each booster network includes resistance means and means for connecting said resistance means to said boost voltage supply and to said transistors.

Claim 43

In a voltage booster circuit, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, control means for increasing the conduction through said variable conducting means in accordance with increases in the current through said line current indicating means and time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means.

Claim 44

In a voltage booster circuit, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, control means for increasing the conduction through said variable conducting means in accordance with increases in the current through said line current indicating means and time-delay means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means.

Claim 45

In a voltage booster circuit, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, control means for increasing the conduction through said variable conducting means in accordance with increases in the current through said line current indicating means, coupling means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means and means for connecting said coupling means between said line current indicating means and said control means.

Claim 46

In a voltage booster circuit, in combination, central office terminal means, subscriber terminal means, means for connecting said terminal means in series with one conductor of a subscriber line, line current indicating means, means for connecting said line current indicating means to the subscriber line, boost voltage supply means, variable conducting means, means for connecting said boost voltage supply means between said terminal means through said variable conducting means, control means for increasing the conduction through said variable conducting means in accordance with increases in the current through said line current indicating means, coupling means for introducing a time-delay between changes in the magnitude or direction of the current through said line current indicating means and resultant changes in the conduction of said variable conducting means and means for connecting said coupling means between said line current indicating means and said control means.