Battery charger control circuit for telephone transmission systems

• US 3,968,333 A
• Filed: 09/18/1973
• Issued: 07/06/1976
• Est. Priority Date: 09/18/1973
• Status: Expired due to Term

• Current Assignee: Superior Continental Corporation
• Original Assignee: Superior Continental Corporation
• Inventors: Simokat, Frank L., Baker, LeRoy S.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/398,448
• Time in Patent Office: 1,022 Days
• Field of Search: 179/2.5 R, 179/16 A, 179/16 AA, 179/26, 179/81 R, 179/175.3 R, 179/175.2 R, 179/175.2 C, 320/2
• US Class Current: 379/413
• CPC Class Codes: H04M 19/08 with current supply sources at the substations generating ringing current H04M19/04

Abstract

A telephone transmission system in which a telephone transmission line connects a central office d.c. power source to a battery charging control circuit to apply an input voltage to the control circuit, in which a battery charger connects a rechargeable battery to said control circuit to draw battery charging current from the transmission line under the control of the control circuit, in which the control circuit is rendered effective by a lowering of the input voltage to at least a predetermined value to effectively disconnect the battery charger and the battery from the transmission line for a period that exceeds the interval in which the input voltage is lowered.

Claims

1. A method of temporarily electrically disconnecting a rechargeable, equipment-powering battery from a plural conductor transmission line in a telephone transmission circuit in which a telephone is electrically connected by said line to a central office, and in which said battery is located remotely from the central office and is normally electrically connected to said line when said line is idle to be recharged by current fed down said line from a d.c. power source which is located at said central office, said method comprising the steps of electrically disconnecting said battery from said line and charging a capacitor either upon transferring said telephone from its on-hook condition to its off-hook condition or upon disconnecting said line from said source, and utilizing the charge stored on said capacitor to temporarily delay the reconnection of said battery to said line following establishment of a condition in which said telephone is in its on-hook condition and said line is electrically connected to a selected power source.

2. A method of temporarily electrically disconnecting a rechargeable, equipment-powering battery from a plural conductor transmission line in a telephone transmission circuit in which a telephone is electrically connected by said line to a central office, in which said battery is electrically connected to said line remotely from said central office, in which a d.c. power supply source is electrically connected to said line at said central office to develop an applied voltage for charging said battery when said telephone is in its on-hook condition, and in which said applied voltage decreases from an idle line value which exists when said telephone is in its on-hook condition and said line is idle to a predetermined value when said telephone is transferred to its off-hook condition to close its hookswitch, said method comprising the steps of electrically disconnecting said battery from said line when said applied voltage decreases to at least said predetermined value, charging a capacitor, and utilizing the charge stored on said capacitor to temporarily delay the reconnection of said battery to said line for a predetermined time period following restoration of the decreased voltage to said idle line value, said predetermined period being longer than the duration of each dialing pulse which transmitted by said line from said telephone to said central office.

3. A method of temporarily electrically disconnecting a rechargeable, equipment-powering battery from a plural conductor transmission line in a telephone transmission circuit in which a telephone is electrically connected by said line to a central office, and in which said battery is located remotely from said central office and is normally electrically connected to said line when said line is idle to be recharged by current fed down said line from a d.c. power source which is located at said central office, said method comprising the steps of electrically disconnecting said battery from said line and charging a capacitor either when said telephone is transferred from its on-hook condition to its off-hook condition or when said line is electrically disconnected from said source, and utilizing the charge stored on said capacitor to temporarily delay the reconnection of said battery to said line for a predetermined time period following the establishment of a condition in which said telephone is in its on-hook condition and said line is electrically connected to a selected power source.

4. A method of temporarily disconnecting a rechargeable, equipment-powering battery from a plural conductor transmission line in a telephone transmission circuit in which a telephone is electrically connected by said line to a central office, in which a central office d.c. power supply source is electrically connected to said line to apply a voltage across the conductors of said line, and in which said battery is located remotely from said central office and is normally electrically connected to said line when said line is idle to be charged by current which is fed down said line from said central office d.c. power source, said method comprising the steps of charging a first capacitor during the period when said line is idle and electrically connected to said power source, effectively disconnecting said battery from said line and transferring a portion of the charge on said first capacitor to charge a second capacitor when said telephone is transferred to its off-hook condition or when said line is electrically disconnected from said power source, and utilizing the charge stored on said second capacitor to temporarily delay the reconnection of said battery to said line for a predetermined time period following the establishment of a condition in which said telephone is in its on-hook condition and said line is electrically connected to a selected power source.

5. A method of temporarily electrically disconnecting a rechargeable, equipment-powering battery from a plural conductor transmission line in a telephone transmission circuit in which a telephone is electrically connected by said line to a central office, in which a central office d.c. power supply source is electrically connected to said line to apply a voltage across the conductors of said line, and in which said battery is located remotely from said central office and is normally electrically connected to said line when said line is idle to be charged by current which is fed down said line from said central office d.c. power source, said method comprising the steps of feeding current from said source to store a charge on a first capacitor during the period when said line is idle and electrically connected to said power source, effectively electrically disconnecting said battery from said line and transferring a portion of the charge on said first capacitor to charge a second capacitor when said telephone is transferred to its off-hook condition or when said line is electrically disconnected from said power source, and utilizing the charge stored on said second capacitor to temporarily delay the reconnection of said battery to said line for a predetermined time period following the occurrence of a condition in which said telephone is in its on-hook condition and said line is connected either to said central office d.c. power source or to a power source in line insulation testing equipment.

6. A method of temporarily electrically disconnecting a rechargeable, equipment-powering battery from a plural conductor transmission line in a telephone transmission circuit in which a telephone is electrically connected by said line to a central office, in which a central office d.c. power supply source is electrically connected to said line to apply a voltage across the conductors of said line, and in which said battery is located remotely from said central office and is normally electrically connected to said line when said line is idle to be charged by current which is fed down said line from said central office d.c. power source, said method comprising the steps of feeding current from said source to store a charge on a first capacitor during the idle line period when said telephone is in its on-hook condition and said line is electrically connected to said source, effectively electrically disconnecting said battery from said line and transferring a portion of the stored charge to charge a second capacitor when the voltage along said line decreases by at least a pre-selected amount from an idle line value which is present when said telephone is in its on-hook condition and said line is electrically connected to said source, and utilizing the charge stored on said second capacitor to temporarily delay the reconnection of said battery to said line for a predetermined time period following restoration of the decreased voltage to at least a pre-selected value.

7. A method of effecting electrical connections for conducting a line insulation test on a plural conductor transmission line in a telephone transmission system having a central office d.c. power source which is normally electrically connected to said line, and a rechargeable battery which is normally electrically connected to said line remotely from a central office to draw battery-charging current from said source when said line is idle, said method comprising the steps of electrically disconnecting said line from said central office d.c. power source, thereafter electrically connecting said line to line insulation testing equipment, effectively electrically disconnecting said battery from said line substantially at the time when said line is electrically disconnected from said central office d.c. power source, charging a capacitor during the break time when said line is connected neither to said central office d.c. power source nor to said test equipment, and utilizing the charge stored on said capacitor during the break time to temporarily delay the reconnection of said battery to said line following the connection of said line to said test equipment.

8. A method of effecting electrical connections for conducting a line insulation test on a plural conductor transmission line in a telephone transmission system having a telephone connected by said line to a central office, a central office d.c. power source which is normally electrically connected to said line, and a rechargeable battery which is normally electrically connected to said line remotely from a central office to draw battery-charging current from said source when said line is idle, said method comprising the steps of storing a charge on a first capacitor during the period when said telephone is in its on-hook condition and said central office d.c. power source is electrically connected to said line, electrically disconnecting said line from said central office d.c. power source, thereafter electrically connecting said line to line insulating testing equipment, effectively electrically disconnecting said battery from said line substantially at the time when said line is electrically disconnected from said central office d.c. power source, transferring a portion of the charge stored on said first capacitor to charge a second capacitor during the break time when said line is connected neither to central centrall office d.c. power source nor to said test equipment, and utilizing the charge stored on said second capacitor during the break time to temporarily delay the reconnection of said battery to said line following the connection of said line to said test equipment.

9. A telephone transmission system comprising a transmission line, a telephone electrically connected by said line to a central office, a d.c. power source located at said central office and electrically connected to said line to provide a supply of direct current to said line, an equipment-powering, rechargeable battery, and means electrically connecting said battery to said line remotely from said central office and comprising a disconnect control circuit normally conditioned when said line is idle to pass direct durrent which is fed down said line from said source for recharging said battery, said telephone having the effect upon being transferred from its on-hook condition to its off-hook condition to decrease the transmission line voltage which is applied to said control circuit from an idle line value to a predetermined value, and said control circuit comprising a capacitor, means for accumulating a charge on said capacitor when said line is idle, circuit means responsive to a decrease in the applied transmission line voltage to said predetermined value or momentarily to zero to complete a discharging circuit for discharging said capacitor and to stop the flow of battery charging current from said line, and said circuit means including means rendered effective by the discharging of said capacitor to temporarily keep battery charging current from being drawn from said line for a pre-selected time interval which is independent of the charging time constant for said capacitor and which starts with the restoration of said applied transmission line voltage to a value greater than said predetermined value.

10. In a telephone transmission system, a two-conductor transmission line, a telephone connected by said line to a central office, and a central source of d.c. power electrically connected across the conductors of said line to apply a d.c. voltage across said conductors, a rechargeable battery located remotely from said central office for powering equipment which is also remote from said central office, a battery charger connected to said battery for charging said battery, and a battery charger control circuit connected between said line and said charger and comprising a rectifier having a pair of output terminals, means connecting said rectifier to said line to provide a d.c. voltage across the rectifier output terminals, said rectifier being effective to maintain the voltage at one of its output terminals substantially constant with respect to ground, a semiconductor device having first and second terminals and a control terminal for controlling flow of current between said first and second terminals, said first terminal being connected to said one of said rectifier output terminals, and said charger being connected between said second terminal and the other of said rectifier output terminals, means connecting said control terminal to said other of said rectifier output terminals to condition said device in a conducting state in which it provides for the flow of current through said first and second terminals to power said charger when said telephone is in its on-hook condition and said source is connected across said conductors, and circuit means connected to said semiconductor device and rendered effective by the transfer of said telephone from its on-hook condition to its off-hook condition to temporarily switch said semiconductor device to a non-conductive state, said semiconductor device being effective in its non-conducting state to substantially terminate the flow of current between said first and second terminals.

11. The telephone transmission system defined in claim 10 wherein said semiconductor device is a transistor.

12. In a telephone transmission system, a two-conductor transmission line, a telephone connected by said line to a central office, and a central office source of d.c. power connected across the conductors of said line to apply a d.c. voltage across said conductors, a rechargeable battery located remotely from said central office for powering equipment which is also remote from said central office, a battery charger connected to said battery for charging said battery, and a battery charger control circuit connected between said line and said charger and comprising a rectifier having a pair of output terminals, means connecting said rectifier to said line to provide a d.c. voltage across said output terminals of said rectifier, said rectifier being effective to maintain the voltage at one of its output terminals substantially constant with respect to ground, a first transistor having first, second, and third terminals, said first terminal being connected to said one of said rectifier output terminals, and said charger being connected to said second terminal and to the other of said rectifier output terminals, means connecting said third terminal to the other of said rectifier output terminals to bias said first transistor into a conducting state that supplies current to said charger when said telephone is in its on-hook condition and said source is connected across said conductors, a second transistor connected to said first transistor, said second transistor being effective in its conducting state to switch said first transistor to its non-conducting state, said first transistor being effective in its non-conducting state to substantially terminate the flow of current to said charger, and circuit means rendered effective by the transfer of said telephone from its on-hook condition to its off-hook condition to switch said second transistor to its conducting state, said circuit means also being rendered effective by the transfer of said telephone back to its on-hook condition to switch said second transistor to its non-conducting state following a preselected time delay after said telephone is returned to its on-hook condition.

13. In combination with a battery charger, a battery charger control circuit for connecting said battery charger to a transmission line in a telephone transmission circuit for drawing current from a central office d.c. power to power said battery charger when a telephone, which is connected by said line to said central office, is in its on-hook condition, said battery charger control circuit comprising a rectifier having a pair of output terminals, means adapted to connect said rectifier to said line to provide a d.c. voltage across the output terminals of said rectifier, said rectifier being effective to maintain the voltage at one of its output terminals substantially constant with respect to ground, a semiconductor device having first and second terminals and a control terminal, said first terminal being connected to said one of said rectifier output terminals, and said charger being connected to said second terminal and to the other of said rectifier output terminals, means connecting said control terminal to said other of said rectifier terminals for conditioning said semiconductor device to supply current to said charger, and further means connected to said control terminal and rendered effective by the transfer of said telephone to its off-hook condition to substantially temporarily terminate the flow of current between said first and second terminals for a time period that exceeds the interval during which said telephone is in its off-hook condition.

14. The combination defined in claim 13, wherein said semiconductor device is a transistor.

15. In combination with a battery charger, a battery charger control circuit for connecting said battery charger to a transmission line in a telephone transmission circuit for drawing current from a central office d.c. power source to power said battery charger when a telephone, which is connected to said transmission line is in its on-hook condition, said battery charger control circuit comprising a rectifier having a pair of output terminals, means for connecting said rectifier to said line to provide a d.c. voltage across the output terminals of said rectifier, said rectifier being effective to maintain the voltage at one of its output terminals substantially constant with respect to ground, a first transistor having first, second and third terminals, asaid first terminal being connected to said one of said rectifier output terminals, and said charger being connected to said second terminal and to the other of said rectifier output terminals, means connecting said third terminal to said other of said rectifier output terminals for biasing said first transistor into a conducting state which feeds current to said charger, a second transistor connected to said first transistor, said second transistor being effective in its conducting state to condition said first transistor to substantially terminate the supply of current to said charger, and circuit means connected to said rectifier and said second transistor and responsive to the transfer of said telephone to its off-hook condition to temporarily switch and second transistor to its conducting state for a period that exceeds the interval during which said telephone is in its off-hook condition.

16. In a telephone transmission system, a plural conductor transmission line, a central office d.c. source of power electrically connected across the conductors of said line to apply a voltage across said conductors, a rechargeable, equipment-powering battery located remotely from said central office, a control circuit for electrically connecting said battery to said line to draw battery-charging current from said source, line testing equipment, and means for electrically disconnecting said line from said source and for connecting said line to said testing equipment after said line a certain break time after the disconnection of said line from said source, said control circuit comprising a capacitor, means for charging said capacitor during the break time in which said line is disconnected from both said source and said test equipment, and means for utilizing the charge stored on said capacitor to temporarily prevent battery charging current from being drawn from said line for a predetermined time following the connection of said line to said test equipment.

17. The telephone transmission defined in claim 16 wherein said means for charging said capacitor comprises a further capacitor and means for charging said further capacitor when said line is idle and electrically connected to said source.

18. The telephone trasmission system defined in claim 16 wherein said test equipment provides for the line insulation testing of said transmission line.

19. In a battery disconnect control circuit for electrically connecting a rechargeable, equipment-powering battery to a plural conductor transmission line which electrically connects a telephone to a central office and which is electrically connected to a d.c. power source at the central office, said battery disconnect control circuit comprising a capacitor, circuit means controlled by the applied voltage on said line for passing current which is fed down said line from said source to charge said battery when said line is idle, said circuit means being responsive to a decrease in said voltage to a pre-selected magnitude or zero to prevent battery charging current from being drawn from said line and to charge said capacitor, and switching means forming a part of said circuit means and conditioned by the charge on said capacitor to continue to temporarily prevent battery charging current from being drawn from said line for a predetermined interval after said voltage is restored to a value which is greater than said pre-selected magnitude.

20. In a telephone transmission system, a plural conductor transmission line for connecting a telephone to a central office, a central office source of d.c. power electrically connected across the conductors of said line to apply voltage across said conductors, a rechargeable equipment-powering battery located remotely from said central office, and a control circuit, said conductors being connected to said control circuit remotely from said central office to apply an input voltage across said control circuit, said control circuit comprising first switching means which is effective in a first condition to connect said battery to said line to draw battery charging current from said line and which is effective in a second condition to effectively disconnect said battery from said line, first and second capacitors, means for charging said first capacitor during the period when said telephone is in its on-hook condition, second switching means responsive to a lowering of said input voltage that is caused by the transfer of said telephone to its off-hook condition or by the disconnection of said line from said source to complete a circuit for switching said first switching means to said second condition and for transferring a portion of the charge stored on said first capacitor to charge said second capacitor, said second switching means being further responsive to the restoration of the lowered input voltage to at least a pre-selected value to effectively open the circuit that it completed in response to the lowering of said input voltage, and means for applying the charge on said second capacitor to temporarily delay the transfer of said first switching means back to said first condition following the restoration of said input voltage to at least said preselected value.

21. In a telephone transmission system having a transmission line, a telephone connected by said line to a central office, a central office source of d.c. power electrically connected to said line, and a rechareable, equipment-powering battery located remotely from said central office, a disconnect control circit, said battery being electrically connected through said control circuit to said line to draw battery-charging current from said source when said line is idle and electrically connected to said source, and said control circuit being responsive to the transfer of said telephone from its on-hook condition to its off-hook condition to prevent battery charging current from being drawn from said line, said control circuit comprising a capacitor, means for charging said capacitor upon transferring said telephone from its on-hook condition to its off-hook condition, and means utilizing the charge on said capacitor to prevent battery charging current from being drawn from said line for a predetermined time interval following return of said telephone to its on-hook condition.

22. In a telephone transmission system having a transmission line, a telephone connected by said line to a central office, a central office source of d.c. power electrically connected to said line, and a rechargeable equipment-powering battery located remotely from said central office, a disconnect control circuit, said battery being electrically connected through said control circuit to said line to draw battery-charging current from said source when said line is idle, and said control circuit being responsive to the transfer of said telephone from its on-hook condition to its off-hook condition to electrically disconnect said battery from said line, said control circit comprising first and second capacitors, means for charging said first capacitor when said line is idle, means for transferring at least a portion of the charge stored on said first capacitor to charge said second capacitor in response to the transfer of said telephone from its on-hook condition to its off-hook condition, and means utilizing the charge stored on said second capacitor to temporarily delay the reconnection of said battery to said line for a predetermined time period following the restoration of said line to its idle condition by returning said telephone to its on-hook condition.