Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Testing of subscriber loop or terminal
Reexamination Certificate
2001-02-23
2003-06-03
Kuntz, Curtis (Department: 2643)
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Testing of subscriber loop or terminal
C379S002000, C379S001040
Reexamination Certificate
active
06574311
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to testing of telephone lines using time-domain reflectometry.
2. Description of the Prior Art
A typical telephone subscriber receives telephony services over a pair of copper wires at frequencies below 4 kHz. Recent transmission technology, such as digital subscriber line (DSL), has expanded the possible use of copper wires to enable high speed data transmissions using frequencies up to and beyond 1 MHz. However, installation practices and defects or anomalies in copper wire pairs can limit or distort the transmission carrying capacity thereof. To test for possible problems in copper wire pairs, a single-ended test is desired to avoid or minimize the time and expense of dispatching repair personnel to the far end of a copper wire pair for a dual-ended test.
Time-domain reflectometry (TDR) is a well-known and generally available technique that can be utilized to identify problems associated with copper wire pairs. TDR apparatus and methods are disclosed generally in U.S. Pat. Nos. 5,121,420 to Marr et al.; 5,369,366 to Piesinger; 5,461,318 to Borchertetal.; 5,521,512 to Hulina; 5,530,365 to Lefeldt; and 5,650,728 to Rhein et al.
Traditional TDR techniques, however, have several limitations. Specifically, present TDR techniques include transmitting an electrical pulse down the copper wire pair and measuring the time to receive a return pulse. This return pulse occurs when the transmitted pulse encounters a change in impedance of the copper wire pair due to some discontinuity therein. Common causes of discontinuities in the copper wire pair include: splices where different copper wire pairs are joined together; moisture on or around the copper wire pair; connection of bridged taps to the copper wire pair; or terminations, such as telephones, that may be connected to the copper wire pair.
Conventional TDR is limited by the energy content of the pulse and the frequency dispersion of the pulse as it travels along the length of the copper wire pair and back. These limitations include: technical difficulty in coupling all of the source TDR energy pulses to the copper wire pair; very low return signal levels due to losses associated with round trip pulse transmission along the copper wire pair; “smearing” of return pulses due to multiple reflections in both directions of pulse travel, and a low signal-to-noise ratio (SNR) on a lossy copper wire pair.
It is, therefore, an object of the present invention to provide an apparatus and method for detecting a loop configuration of a telephone line. This loop configuration can include: the length of the telephone line; the position of a bridged tap connected to the telephone line; and/or the length of the bridged tap connected to the telephone line. Still other objects of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.
SUMMARY OF THE INVENTION
Accordingly, we have invented an apparatus for detecting discontinuities of a telephone line. The apparatus includes means for electrically stimulating a telephone line and a return detector for acquiring plural samples of data corresponding to the response of the telephone line to the electrical stimulation during at least one sample interval. A controller stores the plural samples of data and forms therefrom a plurality of windows of sampled data with each window including a unique subset of the plural samples of data. An activity finder receives each of the plurality of windows and outputs a weighting value for each window as a function of at least one of (i) the numerical values of the unique subset of the plural samples of data of the window; (ii) the relative position of the window in the plurality of windows; and (iii) the numerical range of values of the unique subsets of the plural samples of data forming the window. The controller can detect a predetermined event from a subset of the weighting values and can select one of the plurality of windows as a function of one of the weighting values of the subset of weighting values. An event identifier processes the one window and outputs to the controller as a function thereof a first value which is a numerical probability that the one window represents a discontinuity of the telephone line. The event identifier can also output as a function of the one window a second value which is a numerical probability that the one window represents an end-of-line (EOL) of the telephone line.
Preferably, the first value is a bridged tap (BT) value which relates to a position on the telephone line where a BT is connected. The first value can also relate to a position on the telephone line where a load coil is connected; a position on the telephone line where there is a change in the wire gauge of the wire forming the telephone line; and/or a position on the telephone line where there are faults or partially broken leads in the wire forming the telephone line. Preferably, the second value, also known as an EOL value, relates to the EOL of the telephone line. When the first value is a BT value, a BT length identifier processes the one window when the BT value is greater than the EOL value and outputs to the controller as a function of the BT value a BT length value. An EOL locator processes the one window and at least two of the BT value, the EOL value, the BT length value, the one weighting value of the subset of weighting values, the range of numerical values of the unique subset of the plural samples of data, and the relative location of the one window in the plurality of windows and outputs to the controller as a function thereof an EOL length value. When the BT value is greater than the EOL value, the relative position of the one window in the plurality of windows corresponds to a position on the telephone line where the BT is connected. When the EOL value is greater than the BT value, the relative position of the one window in the plurality of windows corresponds to a length of the telephone line.
The electrical stimulation can include a first pulse corresponding to a first section of the telephone line and a second pulse corresponding to a second section of the telephone line which is partially coincident with the first section of the telephone line. The response of the telephone line includes a first waveform corresponding to a response of the telephone line to the first pulse and a second waveform corresponding to a response of the telephone line to the second pulse. A part of the first waveform and a part of the second waveform represent the response of the telephone line where the first section of the telephone line is partially coincident with the second section of the telephone line.
A first subset of the plurality of windows can be associated with the part of the first waveform and a second subset of the plurality of windows can be associated with the part of the second waveform. The activity finder can determine for each window of the first subset of the plurality of windows a first weighting value associated with the first waveform and can determine for each window of the second subset of the plurality of windows a second weighting value associated with the second waveform. Each first weighting value forms with one of the second weighting values a pair of weighting values having their respective windows including samples of data related to the same section of the telephone line.
A BT counter can be included for receiving the weighting values of the plurality of windows and for forming from the received weighting values a first trace which includes weighting values associated with the first waveform and weighting values associated with the second waveform and which excludes for each pair of related first and second weighting values the minimum thereof. The BT counter also forms from the received weighting values a second trace which includes weighting values associated with the first waveform and weighting values associated with the second waveform and which excludes for each
Detka Christopher S.
Nero, Jr. Regis J.
Ross Rebecca Webb
Kuntz Curtis
Taylor Barry W
Tollgrade Communications, Inc.
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