Method and apparatus for analyzing resistive faults on telephones cables

• US 5,606,592 A
• Filed: 05/02/1995
• Issued: 02/25/1997
• Est. Priority Date: 06/16/1993
• Status: Expired due to Term

• Current Assignee: Greenlee Textron Incorporated (Emerson Electric Company)
• Original Assignee: Industrial Technology Inc. (Textron Inc)
• Inventors: Galloway, George G., Siglinger, Paul R.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): Shankar, Vijay
• Application Number:
  US08/432,667
• Time in Patent Office: 665 Days
• Field of Search: 379/5, 379/21, 379/22, 379/24, 379/26, 379/27, 379/30, 379/1, 379/6, 379/20, 379/34, 324/52, 324/60, 324/509, 324/512, 324/522, 324/523, 324/527, 324/519, 324/111, 324/429, 324/433, 324/616, 324/713
• US Class Current: 379/30
• CPC Class Codes: H04M 1/24 Arrangements for testing
• CPC Class Codes: H04M 1/74 with means for reducing interference; with means for reducing effects due to line faults
• CPC Class Codes: H04M 3/30 for subscriber's lines , for the local loop

Abstract

Resistive faults are analyzed on a conductor in a telephone line by first charging the conductor to an initial voltage. The conductor is allowed to float for a finite amount of time, allowing some of the charge on the conductor to leak through any resistive fault. Then, the voltage of the conductor is measured and compared to the initial voltage. Loss of voltage indicates a resistive fault. This information can be used to provide an indication of the accuracy of a capacitance measurement and can be used to correct the capacitance measurement to account for the error due to the resistive fault.

Claims

1. A method of analyzing a resistive fault on a telephone conductor, comprising the steps of:

a) charging said telephone conductor to an initial charge, said step of charging said telephone conductor to an initial charge further comprises the step of charging said telephone conductor to an initial voltage;

b) after charging said telephone conductor to said initial charge, discontinuing the charging of said telephone conductor and floating said telephone conductor without a load for an amount of time; and

c) at the end of said amount of time, determining if any charge has leaked from said telephone conductor, wherein the leakage of charge from said telephone conductor indicates the presence of a resistive fault on said telephone conductor;

d) said step of determining if any charge has leaked from said telephone conductor further comprises the steps of determining the charge on said telephone conductor at the end of said amount of time and comparing said determined charge to said initial charge;

e) said step of determining the charge on said telephone conductor further comprises the step of determining the voltage on said telephone conductor; and

f) said step of comparing said determined charge to said initial charge further comprises the step of comparing said determined voltage to said initial voltage.

2. The method of claim 1 further comprising the steps of:

a) comparing said determined voltage to a threshold voltage; and

b) if said determined voltage is smaller than said threshold voltage, then providing an indication of error.

3. The method of claim 1 further comprising the step of determining the amount of error from said initial and said determined charges.

4. The method of claim 3 further comprising the steps of:

a) measuring a capacitance of said telephone conductor by measuring the current needed to either charge said telephone conductor to said initial voltage or discharge said telephone conductor from said initial voltage; and

b) correcting said capacitance measurement using said determined amount of error.

5. A method of analyzing a resistive fault on a telephone conductor, comprising the steps of:

a) charging said telephone conductor to an initial charge;

b) after charging said telephone conductor to said initial charge, discontinuing the charging of said telephone conductor and floating said telephone conductor without a load for an amount of

c) at the end of said amount of time, determining if any charge has leaked from said telephone conductor, wherein the leakage of charge from said telephone conductor indicates the presence of a resistive fault on said telephone conductor;

d) said step of determining if any charge has leaked from said telephone conductor further comprises the steps of;

i) determining the amount of charge that has leaked from said telephone conductor;

ii) comparing said amount of charge that has leaked from said telephone conductor to a threshold amount; and

iii) if said amount of charge that has leaked from said telephone conductor is larger than said threshold amount, then providing an indication of error.

6. A method of measuring capacitance of a telephone conductor, comprising the steps of:

a) charging said telephone conductor to an initial charge;

b) floating said charged telephone conductor for an amount of time, said telephone conductor being unconnected to a load or a charging source while said telephone conductor is floating;

c) alter said amount of time has passed, determining if any charge has leaked from said telephone conductor, wherein if any charge has leaked from said telephone conductor, then said telephone conductor has a resistive fault;

d) changing the charge on said telephone conductor;

e) integrating the change in charge on said telephone conductor so as determine said capacitance of said telephone conductor;

f) if in step c), charge had leaked from said telephone conductor, then correcting said determined capacitance to compensate for said resistive fault.