System and method of determining cable characteristics

• US 5,128,619 A
• Filed: 09/05/1991
• Issued: 07/07/1992
• Est. Priority Date: 04/03/1989
• Status: Expired due to Fees

• Current Assignee: ROLM Co. (Siemens AG)
• Original Assignee: Harry L. Cochrane, John T. Chapman, Roger A. Bjork, Timothy L. Wilson
• Inventors: Chapman, John T., Wilson, Timothy L., Cochrane, Harry L., Bjork, Roger A.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Regan, Maura K.
• Application Number:
  US07/759,044
• Time in Patent Office: 306 Days
• Field of Search: 324/533, 324/532, 324/534, 379/6, 379/24, 379/26, 379/30, 379/32
• US Class Current: 324/533
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04M 3/30 for subscriber's lines , for the local loop
• CPC Class Codes: H04M 3/306 for frequencies above the voice frequency, e.g. xDSL line qualification test methods, test equipment and test arrangements for subscriber lines using xDSL modems H04M3/304; systems modifying transmission characteristics according to link quality H04L1/0001; monitoring and/or testing of line transmission systems H04B3/46

Abstract

A method of and system for automatically determining length, attenuation, impedance and existence of bridge taps on installed communication cable having access to only one end of the cable. A waveform, which includes incident and reflected pulses, is analyzed to determine the presence of significant pulses. The presence of only one positive significant pulse indicates the absence of any discontinuities and facilitates the calculation of a signal-to-noise ratio which determines whether the cable will support the operation of digital communication thereon. The presence of more than one positive significant pulse or a negative pulse indicates the presence of at least one fault on the cable which prevents the operation of digital communication on the cable.

Claims

1. A system for determining whether a communication cable will support digital communications thereon, said system includes:

means for transmitting a pulse over said communications cable;

means for detecting responsive to said transmitted pulse at least one pulse reflected from said communication cable;

means for derivative characteristics of said at least one reflected pulse, the derivative characteristics including a first derivative, a second derivative, and a third derivative; and

means for analyzing said at least one reflected pulse and its derivative characteristics to determine whether said communication cable will support digital communications thereon, said analysis being performed from one end of said communication cable.

2. The system as recited in claim 1 further includes means for determining whether said detected at least one reflected pulse is significant.

3. The system as recited in claim 2 wherein said analyzing means includes means for determining the number of significant pulses detected.

4. The system as recited in claim 3 further includes means for calculating impedance characteristics of said communication cable.

6. The system as recited in claim 3 wherein one negative significant or more than one positive significant pulse was detected and further includes means for determining a location of a fault which exists on the communication cable which is indicated by a starting point of said negative significant pulse or a starting point of a first of said more than one positive significant pulse.

5. A system for determine whether a communication cable will support digital communications thereon, said system includes:

means for transmitting a pulse over said communications cable;

means for detecting responsive to said transmitted pulse at least one pulse reflected from said communication cable;

means for deriving derivative characteristics of said at least one reflected pulse;

means for calculating impedance characteristics of said communication cable;

means for analyzing said at least one reflected pulse and its derivative characteristics to determine whether said communication cable will support digital communications thereon, said analysis being performed from one end of said communication cable; and

means for determining whether said detected at least one reflected pulse is significant;

wherein said analyzing means includes means for determining the number of significant pulses detected; and

wherein only one positive significant pulse was detected and further includes;

means for determining a length of said communication cable;

means for calculating attenuation characteristics of said communication cable; and

means, responsive to the length, the impedance and the attenuation of said cable, for calculating a signal-to-noise ratio for said communication cable.

7. A method of determining whether a communication cable will support digital communications thereon, said method includes the steps of:

transmitting a pulse over said communications cable;

detecting responsive to said transmitted pulse at least one pulse reflected from said communication cable;

deriving derivative characteristics of said at least one reflected pulse, the derivative characteristics including a first derivative, a second derivative, and a third derivative; and

analyzing said at least one reflected pulse and its derivative characteristics to determine whether said communications thereon, said analysis being performed from one end of said communication cable.

8. The method as recited in claim 7 further includes the step of determining whether said detected at least one reflected pulse is significant.

9. The method as recited in claim 8 wherein said step of analyzing includes the step of determining the number of significant pulses detected.

10. The method as recited in claim 9 further includes the step of calculating impedance characteristics of said communication cable.

12. The method as recited in claim 9 wherein one negative significant or more than one positive significant pulse was detected and further includes the step of determining a location of a fault which exists on the communication cable which is indicated by a starting point of said negative significant pulse or a starting point of a first of said positive significant pulse.

11. A method of determining whether a communication cable will support digital communications thereon, said method includes the steps of:

transmitting a pulse over said communications cable;

detecting responsive to said transmitted pulse at least one pulse reflected from said communication cable;

deriving derivative characteristics of said at least one reflected pulse;

analyzing said at least one reflected pulse and its derivative characteristics to determine whether said communication cable will support digital communications thereon, said analysis being performed from one end of said communication cable;

determining whether said detected at least one reflected pulse is significant;

wherein said step of analyzing includes the step of determining the number of significant pulses detected; and

calculating impedance characteristics of said communication cable; and

wherein only one positive significant pulse was detected and further includes the steps of;

determining a length of said communication cable;

calculating attenuation characteristics of said communication cable; and

using said length, impedance characteristics, and attenuation characteristics of said communication cable to determine whether said cable will support digital communications by calculating a signal-to-noise ratio for said communication cable.

13. A system for determining whether a communication cable will support digital communications thereon, said system includes:

means for transmitting a pulse over said communication cable;

means for detecting responsive to said transmitted pulse at least one pulse reflected from said communication cable;

means for determining whether said detected at least one reflected pulse is significant;

means for analyzing said at least one reflected pulse to determine the number of significant pulses detected;

means for calculating impedance characteristics of said communication cable;

means for determining a length of said communication cable;

means for calculating attenuation characteristics of said communication cable;

means, responsive to a length, the impedance and the attenuation of said cable, for calculating a signal-to-noise ratio for said communication cable; and

means for analyzing said at least one reflected pulse to determine whether said communication cable will support digital communications thereon, said analyzing being performed from one end of said communication cable.

14. A method of determining whether a communication cable will support digital communications thereon, said method includes the steps of:

transmitting a pulse over said communication cable;

detecting responsive to said transmitted pulse at least one pulse reflected from said communication cable;

determining whether said detected at least one reflected pulse is significant;

analyzing said at least one reflected pulse to determine the number of significant pulses detected;

calculating impedance characteristics of said communication cable;

determining a length of said communication cable;

calculating attenuation characteristics of said communication cable;

using said length, impedance characteristics, and attenuation characteristics of said communication cable to calculate a signal-to-noise ratio for said communication cable; and

analyzing said at least one reflected pulse to determine whether said communication cable will support digital communications thereon, said analysis being performed from one end of said communication cable.