Foreign potential checker

• US 4,006,319 A
• Filed: 01/22/1976
• Issued: 02/01/1977
• Est. Priority Date: 01/22/1976
• Status: Expired due to Term

• Current Assignee: AG Communication Systems Corp. (Nokia Corporation)
• Original Assignee: GTE Automatic Electric Laboratories Incorporated
• Inventors: Gartner, Todd H.
• Primary Examiner(s): Olms, Douglas W.
• Application Number:
  US05/651,310
• Time in Patent Office: 376 Days
• Field of Search: 179/175.3 R, 179/175, 324/62, 324/111
• US Class Current: 379/24
• CPC Class Codes: H04B 3/46 Monitoring; Testing

Abstract

The disclosure relates to a monitoring system and method for determining the magnitude of the equivalent voltage source impedance and the magnitude of the equivalent voltage source voltage on a telephone line and switching network of a telephone system. The monitoring system measures the Thevenin source voltage and source impedance to ground on the line by applying two independent voltage conditions to the line and senses the resulting steady state voltages thereby produced in a sensing resistor. The magnitudes of the sensed steady state voltage are thereafter utilized for obtaining the Thevenin source voltage and source impedance magnitudes.

Claims

1. In a telephone system of the type having telephone lines and a switching network, wherein operating voltage sources are maintained on the lines to support telephone communication and wherein each line and the network combine to form an equivalent voltage source and an equivalent voltage source impedance, a monitoring system for indicating the magnitude of the real part of the equivalent voltage source impedance comprising:

a voltage source coupled to a selected one of the lines and operable for providing a constant voltage in opposition to the equivalent source voltage;

voltage sensing means coupled to the side of said voltage source opposite the selected line;

control means for activating and causing said voltage source to provide said constant voltage for a predetermined period of time sufficient to cause a first steady state voltage to appear at said voltage sensing means and for deactivating said voltage source at the end of said predetermined period of time to cause a second steady state voltage to appear at said voltage sensing means;

subtracting means coupled to said sensing means for determining the difference between the magnitudes of said first and second steady state voltages; and

indicating means coupled to said subtracting means for providing an output voltage which is inversely related to said difference determined by said subtracting means and directly related to the real part of said equivalent source impedance for providing a direct indication of the magnitude of the real part of said equivalent source impedance.

2. In a telephone system of the type having telephone lines and a switching network, wherein operating voltage sources are maintained on the lines to support telephone communication and wherein each line and the network combine to form an equivalent voltage source and an equivalent voltage source impedance, a monitoring system for indicating the magnitude of the equivalent voltage source comprising:

a voltage source coupled to a selected one of the lines and selectively operable for providing a constant voltage in opposition to the equivalent source voltage;

voltage sensing means coupled to the side of said voltage source opposite the selected line;

control means for activating and causing said voltage source to provide said constant voltage for a predetermined period of time sufficient to cause a first steady state voltage to appear at said voltage sensing means and for deactivating said voltage source at the end of said predetermined period of time to cause a second steady state voltage to appear at said voltage sensing means;

subtracting means coupled to said sensing means for determining the difference between the magnitudes of said first and second steady state voltages; and

ratio determining means coupled to said voltage sensing means and to said substracting means for determining the ratio of said second steady state voltage to the difference between the magnitudes of said first and second steady state voltages and for providing an output voltage which is directly related to said ratio to thereby provide a direct indication of the magnitude of said equivalent source voltage.

3. In a telephone system of the type having telephone lines and a switching network, wherein operating voltage sources are maintained on the lines to support telephone communication and wherein each line and the network combine to form an equivalent voltage source and an equivalent voltage source impedance, a monitoring system for indicating the magnitudes of the real part of the equivalent voltage source voltage comprising:

a voltage source coupled to a selected one of the lines and operable for providing a constant voltage in opposition to the equivalent source voltage;

voltage sensing means coupled to the side of said voltage source opposite the selected line;

control means for activating and causing said voltage source to provide said constant voltage for a predetermined period of time sufficient to cause a first steady state voltage to appear at said voltage sensing means and for deactivating said voltage source at the end of said predetermined period of time to cause a second steady state voltage to appear at said voltage sensing means;

subtracting means coupled to said sensing means for determining the difference between the magnitudes of said first and second steady state voltages;

ratio determining means coupled to said voltage sensing means and to said subtracting means for determining the ratio of said second steady state voltage to the difference between the magnitudes of said first and second steady state voltages and for providing an output voltage which is directly related to said ratio to thereby provide a direct indication of the magnitude of said equivalent source voltage; and

indicating means also coupled to said subtracting means for providing an output voltage which is inversely related to said difference determined by said subtracting means and directly related to the real part of said equivalent source impedance for providing a direct indication of the magnitude of the real part of said equivalent source impedance.

4. A monitoring system in accordance with claim 3 further comprising switch means coupled between the line to be monitored and said voltage source and also coupled to said control means, and wherein said control means further comprises means for enabling said switch means prior to the activation of said voltage source to thereby connect said voltage source to said line.

5. A monitoring system in accordance with claim 3 wherein said subtracting means comprises a difference amplifier.

6. A monitoring system in accordance with claim 3 wherein said indicating means comprises a reciprocal function module.

7. A monitoring system in accordance with claim 6 wherein said ratio determining means comprises a reciprocal function module coupled to said subtracting means and a multiplication module having a first input coupled to said reciprocal function module and a second input coupled to said sensing means whereby said multiplication module multiplies the reciprocal of said difference voltage by said second steady state voltage to derive said output voltage which is a direct indication of the magnitude of said equivalent source voltage.

8. In a telephone system of the type having telephone lines and a switching network, wherein operating voltage sources are maintained on the lines to support telephone communication and wherein each line and the network combine to form an equivalent voltage source and an equivalent voltage source impedance, a monitoring system for indicating the magnitude range out of a plurality of possible ranges in which the magnitude of the real part of the equivalent voltage source impedance lies comprising:

a voltage source coupled to a selected one of the lines and operable for providing a constant voltage in opposition to the equivalent source voltage;

voltage sensing means coupled to the side of said voltage source opposite the selected line;

control means for activating and causing said voltage source to provide said constant voltage for a predetermined period of time sufficient to cause a first steady state voltage to appear at said voltage sensing means and for deactivating said voltage source at the end of said predetermined period of time to cause a second steady state voltage to appear at said voltage sensing means;

subtracting means coupled to said sensing means for determining the difference between the magnitudes of said first and second steady state voltages and having an output for providing a difference voltage responsive thereto;

a plurality of comparators and a like plurality of reference voltage sources, each said comparator including a reference input, a given respective one of said reference inputs being coupled to a given responsive one of said reference voltage sources to thereby establish the possible plurality of ranges, each of said comparators additionally having another input coupled to said output of said subtracting means, whereby those comparators which are coupled to a reference potential which is less than said difference voltage will provide a first signal and those comparators which are coupled to a reference potential which is greater than said difference voltage will provide a second signal to thereby define the range in which the real part of the equivalent voltage source impedance lies; and

indicating means coupled to said comparators and responsive to said first and second signals for providing a discrete indication of the range in which the magnitude of the real part of the equivalent source impedance lies.

9. In a telephone system of the type having telephone lines and a switching network, wherein operating voltage sources are maintained on the lines to support telephone communication and wherein each line and the network combine to form an equivalent voltage source and an equivalent voltage source impedance, a monitoring system for indicating the magnitude range out of a plurality of possible ranges in which the magnitude of the equivalent voltage source voltage lies comprising:

a voltage source coupled to a selected one of the lines and operable for providing a constant voltage in opposition to the equivalent source voltage;

voltage sensing means coupled to the side of said voltage source opposite the selected line;

control means for activating and causing said voltage source to provide said constant voltage for a predetermined period of time sufficient to cuase a first steady state voltage to appear at said voltage sensing means and for deactivating said voltage source at the end of said predetermined period of time to cause a second steady state voltage to appear at said voltage sensing means;

subtracting means coupled to said sensing means for determining the difference between the magnitudes of said first and second steady state voltages and having an output for providing a difference voltage responsive thereto;

a plurality of comparators, each said comparator having a first input and a second input, each said first input being coupled to said subtracting means output for receiving said difference voltage;

a like plurality of voltage dividers coupled to said sensing means for receiving said second steady state voltage and having an output for providing a predetermined portion of said second steady state voltage as a reference potential, each said divider output providing a different reference potential to thereby establish said ranges, and each respective given one of said divider outputs being coupled to a given respective one of said second inputs of said comparators, whereby with said first inputs being coupled to said difference voltage and with each said second input being coupled to a different reference potential, the ratio of the second steady state voltage to the difference voltage which is directly related to the magnitude of the equivalent voltage source voltage may be determined such that those comparators having a reference potential which is less than said difference voltage will provide a first signal and those comparators which have a reference potential which is greater than said difference voltage will provide a second signal to thereby define the range in which the equivalent voltage source voltage magnitude lies; and

indicating means coupled to said comparators and responsive to said first and second signals for providing a discrete indication of the range in which the equivalent voltage source voltage magnitude lies.

10. In a telephone system of the type having telephone lines and a switching network, wherein operating voltage sources are maintained on the lines to support telephone communication and wherein each line and the network combine to form an equivalent voltage source and an equivalent voltage source impedance, a monitoring system for indicating the magnitude range out of a plurality of possible ranges in which the magnitudes of the real part of the equivalent voltage source impedance and equivalent voltage source voltage lie comprising:

a voltage source coupled to a selected one of the lines and operable for providing a constant voltage in opposition to the equivalent source of voltage;

voltage sensing means coupled to the side of said voltage source opposite the selected line;

control means for activating and causing said voltage source to provide said constant voltage for a predetermined period of time sufficient to cause a first steady state voltage to appear at said voltage sensing means and for deactivating said voltage source at the end of said predetermined period of time to cause a second steady state voltage to appear at said voltage sensing means;

subtracting means coupled to said sensing means for determining the difference between the magnitudes of said first and second steady state voltages and having an output for providing a difference voltage responsive thereto;

a first plurality of comparators and a like first plurality of reference voltage sources, each said comparator of said first plurality including a reference input, a given respective one of said reference inputs being coupled to a given respective one of said reference voltage sources to thereby establish the possible plurality of ranges in which the magnitude of the real part of the equivalent voltage source impedance lies, each of said comparators additionally having another input coupled to said output of said subtracting means, whereby those comparators which are coupled to a reference potential which is less than said difference voltage will provide a first signal and those comparators which are coupled to a reference potential which is greater than said difference voltage will provide a second signal to thereby define the range in which the magnitude of the real part of the equivalent voltage source impedance lies;

a second plurality of comparators, each said comparator of said second plurality having a first input and a second input, each said first input being coupled to said subtracting means output for receiving said difference voltage;

a like second plurality of voltage dividers coupled to said sensing means for receiving said second steady state voltage and having an output for providing a predetermined portion of said second steady state voltage as second reference potentials, each said divider output providing a different second reference potential to thereby establish said ranges in which the magnitude of the equivalent voltage source voltage lies, and each respective given one of said divider outputs being coupled to a given respective one of said second inputs of said second plurality of comparators, whereby with said first inputs being coupled to said difference voltage and with each said second input of said second comparator coupled to a different second reference potential, the ratio of the second steady state voltage to the difference voltage which is directly related to the magnitude of the equivalent voltage source voltage may be determined such that those comparators of the second plurality having a second reference potential which is less than said difference voltage will provide a third signal and those comparators of said second plurality which have a second reference potential which is greater than said difference voltage will provide a fourth signal to thereby define the range in which the real part of the equivalent voltage source voltage magnitude lies; and

indicating means coupled to said first plurality of comparators and to said second plurality of said comparators and responsive to said first, second, third and fourth signals for providing a discrete indication of the ranges in which the magnitudes of the equivalent source impedance and the equivalent voltage source voltage lie.

11. A monitoring system in accordance with claim 10 further comprising switch means coupled between the line to be monitored and said voltage source and also coupled to said control means, and wherein said control means further comprises means for enabling said switch means prior to the activation of said voltage source to thereby connect said voltage source to said line.

12. A monitoring system in accordance with claim 10 wherein said subtracting means comprises a difference amplifier.

13. A monitoring system in accordance with claim 10 further comprising a sample and hold circuit coupled to said sensing means and to said subtracting means for temporarily storing said first steady state voltage wherein said sample and hold circuit is also coupled to said control means, and wherein said control means includes strobe means for causing said sample and hold circuit to transfer said first steady state voltage to said subtracting means.

14. A method of monitoring and indicating the magnitudes of the real part of the equivalent voltage source impedance and the equivalent voltage source voltage in a telephone system of the type having telephone lines and a switching network, wherein operating voltage sources are maintained on the lines to support telephone communication and wherein each line and the network combine to form an equivalent voltage source and an equivalent voltage source impedance, the method comprising the steps of:

applying a constant voltage to a selected line in opposition to the equivalent source voltage for a predetermined period of time sufficient to cause a first steady state voltage to appear on the line,

sensing the magnitude of said first steady state voltage,

terminating the application of the constant voltage until a second steady state voltage appears on the line,

sensing the magnitude of said second steady state voltage;

subtracting the magnitude of said first steady state voltage from the magnitude of said second steady state voltage to thereby provide a difference;

determining the ratio between the magnitude of said second steady voltage to the magnitude of said difference to thereby provide a direct indication of the magnitude of the equivalent voltage source voltage, and

determining the reciprocal of the magnitude of said difference to provide a direct indication of the magnitude of the real part of the equivalent voltage source impedance.

15. A method in accordance with claim 14 wherein said reciprocal of said difference is determined by generating a difference voltage having a magnitude equal to the difference between the magnitude of said first and second steady voltages and thereafter comparing said difference voltage to a plurality of reference voltages to thereby provide an indication as to in which range the magnitude of the real part of the equivalent source impedance lies out of a predetermined plurality of ranges established by said reference voltages.

16. A method in accordance with claim 14 wherein said ratio is determined by generating a difference voltage having a magnitude equal to the difference between the magnitudes of said first and second steady voltages and thereafter comparing said difference voltage to a plurality of predetermined portions of said second steady voltage to thereby provide an indication as to in which range said ratio lies out of a predetermined plurality of ranges established by said plurality of second steady state voltage portions.