Abstract:
Methods and apparatuses are disclosed for locating trouble in a telecommunications network. One method communicates signals from a central office along a local loop. The local loop comprises a ring wire and a tip wire. Voltage polarity between the ring wire and the tip wire is reversed, causing a customer&#39;s wiring to be isolated from the local loop. A test of the local loop may then be remotely performed to determine whether trouble exists in the local loop.

Description:
NOTICE OF COPYRIGHT PROTECTION  
         [0001]    A portion of the disclosure of this patent document and its figures contain material subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, but the copyright owner otherwise reserves all copyrights whatsoever.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention generally relates to telecommunications and, more particularly, to maintenance termination units for locating trouble in a telecommunications network.  
           [0004]    2. Description of the Related Art  
           [0005]    Maintenance termination units help locate trouble in a telecommunications network. When trouble is reported, that trouble may lie within the customer&#39;s premises and/or within the local loop serving the customer. Maintenance termination units have been used to help determine whether the trouble lies within the local loop or within the customer&#39;s premises.  
           [0006]    U.S. Pat. No. 4,529,847 to DeBalko (issued Jul. 16, 1985) shows a maintenance termination unit. This maintenance termination unit comprises a pair of “normally open” voltage switches connected between the ring and tip of the local loop (see Column 3, lines 30-33). When this maintenance termination unit is installed at the customer&#39;s premises, the maintenance termination unit produces a distinctive, periodic DC signal (see Column 4, lines 37-50). When a fault lies within the customer&#39;s premises, this distinctive, periodic DC signal is produced regardless of polarity between the ring and the tip (see Column 4, line 63-Column 5, line 1). If trouble lies within the telecommunications network, then the maintenance termination unit produces either a steady signal (a “hard” fault) or a periodic signal (a “light” fault) (see Column 5, lines 1-7). Because this maintenance termination unit utilizes voltage switches, these switches unfortunately cycle between an open position and a closed position when indicating the presence of a fault (see Column 4, lines 46-48). This periodic signal is often confused by test technicians and leads to an inaccurate diagnosis. This constant cycling, between an open position and a closed position, also leaves little time to conduct a test of the local loop.  
           [0007]    Other maintenance termination units have disadvantages. Many of these prior art maintenance termination units utilize custom, integrated circuitry. These integrated circuits are expensive and time-consuming to design and to fabricate. The expense of designing and fabricating these circuits, in fact, is often cost-prohibitive. Even when an integrated circuit is used, the harsh, ambient environment leads to many field failures. When the integrated circuit fails, the entire maintenance termination unit is then wastefully discarded.  
           [0008]    There is, accordingly, a need for an improved maintenance termination unit that is easier to use, less expensive to design and to manufacture, tolerant of ambient conditions, and cheaper to repair or replace in the field.  
         BRIEF SUMMARY OF THE INVENTION  
         [0009]    The aforementioned problems, and other problems, are reduced by an improved maintenance termination unit. This maintenance termination unit quickly, simply, and inexpensively isolates a customer&#39;s premises from a local loop. This invention is inexpensively designed and manufactured, and this invention is easier to repair and to replace. This invention tolerates extreme cold and hot temperatures, and this maintenance termination unit is largely unaffected by higher humidity climates. This maintenance termination unit utilizes a magnet to isolate a customer&#39;s premises from a local loop. The magnet responds to a reversal in polarity on a customer&#39;s telephone line. When polarity is reversed, the magnet acts to isolate the customer&#39;s premises. A test of the telephone line may then be performed.  
           [0010]    One embodiment of this invention describes a method for determining whether trouble is located in a local loop. This method communicates signals from a central office along the local loop. The local loop comprises a ring wire and a tip wire. Voltage polarity between the ring wire and the tip wire is reversed, causing a customer&#39;s wiring to be isolated from the local loop. A test of the local loop may then be remotely performed to determine whether trouble exists in the local loop.  
           [0011]    Another embodiment of this invention also describes a method for determining whether trouble is located in a local loop. This embodiment communicates signals from a central office along a local loop, and the local loop comprises a ring wire and a tip wire. The polarity between the ring wire and the tip wire is reversed. In response to this reversed polarity, a magnet is utilized to isolate a customer&#39;s wiring from the local loop. The magnet may be any type of magnet, such as a permanent magnetic material, a diamagnetic material, a paramagnetic material, and a ferromagnetic material. When the customer&#39;s wiring is isolated from the local loop, a test of the local loop is remotely performed. The reversed polarity causes the customer&#39;s wiring to be isolated from the local loop, and the local loop may be remotely tested to determine if trouble is located in a local loop.  
           [0012]    Yet another embodiment describes a maintenance termination unit for a telecommunications network. The maintenance termination unit comprises terminals for connecting the maintenance termination unit to a ring wire and to a tip wire of a local loop. The maintenance termination unit also comprises a magnet responding to a change in polarity between the ring wire and the tip wire. When the polarity is changed, the maintenance termination unit isolates a customer&#39;s wiring from the local loop, thus allowing a remote test to determine whether trouble exists in the local loop. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0013]    These and other features, aspects, and advantages of this invention are better understood when the following Detailed Description of the Invention is read with reference to the accompanying drawings, wherein:  
         [0014]    [0014]FIGS. 1 and 2 are schematics illustrating one embodiment of this invention;  
         [0015]    FIGS.  3 - 5  are schematics showing another embodiment of this invention;  
         [0016]    [0016]FIG. 6 is a flowchart showing one method of remotely testing a local loop for trouble; and  
         [0017]    [0017]FIG. 7 is a flowchart showing another method of remotely testing a local loop for trouble. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    [0018]FIGS. 1 and 2 are schematics illustrating one embodiment of this invention. A maintenance termination unit  10  is installed between a central office (CO)  12  and a customer&#39;s premise wiring  14 . Signals are communicated from the central office  12 , along a local loop  16 , and to the maintenance termination unit  10 . As FIG. 1 shows, the local loop  16  comprises a ring wire  18  and a tip wire  20 . The ring wire  18  normally has a positive voltage compared to the tip wire  20 . When the ring wire  18  has a positive voltage compared to the tip wire  20 , the maintenance termination unit  10  allows signals to pass to the customer&#39;s premise wiring  14 . Signals, then, are communicated from the central office  12 , along the ring local loop  16 , through the maintenance termination unit  10 , and to the customer&#39;s premise wiring  14 . The customer&#39;s premise wiring then routes the signals to a communication device (not shown) connected to the customer&#39;s premise wiring  14 .  
         [0019]    [0019]FIG. 2 shows the maintenance termination unit  10  can isolate the customer&#39;s premise wiring  14  from the local loop  16 . When a customer reports trouble with their communications service, the trouble may be within the local loop  16  or within the customer&#39;s premise wiring  14 . The maintenance termination unit  10  allows a telecommunication service provider to isolate the customer&#39;s premise wiring  14  from the local loop  16 . When the maintenance termination unit  10  isolate the customer&#39;s premise wiring  14  from the local loop  16 , the telecommunication service provider may then remotely perform a test of the local loop  16 . If no trouble or fault is detected, then the trouble lies within the customer&#39;s premise wiring  14 .  
         [0020]    A reversed polarity condition activates the maintenance termination unit  10 . The ring wire  18 , as mentioned above, normally has a positive voltage compared to the tip wire  20 . When, however, polarity is reversed, this reversed polarity condition causes the maintenance termination unit  10  to isolate the customer&#39;s premise wiring  14  from the local loop  16 . While the maintenance termination unit  10  maintains the customer&#39;s premise wiring  14  isolated from the local loop  16 , the telecommunication service provider remotely performs a test of the local loop  16 . The telecommunication service provider may perform any test, such as a mechanized loop test (MLT), to help determine whether trouble lies within the local loop  16 .  
         [0021]    Polarity may again be switched before performing the test. A reversed polarity condition, as mentioned above, activates the maintenance termination unit  10 . Once the maintenance termination unit  10  isolates the customer&#39;s premise wiring  14  from the local loop  16 , polarity may again be switched. The ring wire  18  would return to a normally positive voltage compared to the tip wire  20 . Even though the ring wire  18  now has a positive voltage, the maintenance termination unit  10  is designed to maintain an isolation between the customer&#39;s premise wiring  14  and the local loop  16 . This isolation is maintained for a predefined length of time, from milliseconds to hours. Preferably, however, this isolation is only maintained for a “test window.” This “test window” is a predefined, finite amount of time, during which time the remote test is performed. The maintenance termination unit  10 , for example, isolates the customer&#39;s premise wiring  14  for a “test window” of not exceeding about a minute, during which time the test is performed. When the test window expires, the maintenance termination unit  10  restores a connection between the local loop  16  and the customer&#39;s premise wiring  14 .  
         [0022]    FIGS.  3 - 5  are schematics showing a second embodiment of this invention. FIGS. 3 and 4 are sectional views of a maintenance termination unit  22  for isolating a customer&#39;s premise wiring from the local loop (shown, respectively, as reference numerals  14  and  16  in FIGS. 1 and 2). FIGS. 3 and 4 are also enlarged views to emphasize the functional characteristics of this maintenance termination unit  22 . The maintenance termination unit  22  comprises a first terminal  24  and a second terminal  26  for connecting to the local loop. The first terminal  24 , for example, connects to the ring wire  18 , and the second terminal  26  connects to the tip wire  20  of the local loop. The maintenance termination unit  22  also comprises a third terminal  28  and a fourth terminal  30  for connecting to the customer&#39;s premise wiring  14 .  
         [0023]    The maintenance termination unit  22  also comprises a magnet  32 . The magnet  32  responds to a change in polarity between the ring wire  18  and the tip wire  20 . The magnet  32  is traditionally understood to have “north pole” at one end  34 . The magnet is also understood to have a “south pole” at another end  36 . Positive charges gather at the north pole  34 , while negative charges gather at the south pole  36 . When the polarity of the ring wire  18  causes negative charges to gather at the first terminal  24 , these negative charges attract the positive charges gathered at the north pole  34  of the magnet  32 . The corresponding polarity of the tip wire  20  causes positive charges to gather at the second terminal  26 , and these positive charges attract the negative charges gathered at the south pole  36 . This attractive force causes the magnet  32  to move.  
         [0024]    The magnet  32 , however, may also be repelled. When the polarity of the ring wire  18  causes positive charges to gather at the first terminal  24 , these positive charges repel the positive charges gathered at the north pole  34  of the magnet  32 . The corresponding polarity of the tip wire  20  causes negative charges to gather at the second terminal  26 , and these negative charges attract the positive charges gathered at the south pole  36 . This repelling force also causes the magnet  32  to move.  
         [0025]    The polarity of the ring wire  18  and the tip wire  20  may then be used to move the magnet  32 . This movement of the magnet  32  is used in this second embodiment to isolate the customer&#39;s premise wiring  14  from the local loop  12 . This movement of the magnet  32  is also used to connect the customer&#39;s premise wiring  14  to the local loop  12 . FIG. 3, for example, shows the polarity of the ring wire  18  causing negative charges to gather at the first terminal  24 . These negative charges attract the positive charges gathered at the north pole  34  of the magnet  32 . The corresponding polarity of the tip wire  20  causes positive charges to gather at the second terminal  26 , and these positive charges attract the negative charges gathered at the south pole  36 . FIG. 3, then, shows that this attractive force causes the magnet  32  to move and connect the first terminal  24 , and thus the ring wire  18 , to the third terminal  28 . This attractive force, likewise, causes the magnet  32  to move and connect the second terminal  26 , and thus the tip wire  20 , to the fourth terminal  30 . The polarity of the ring wire  18  and the tip wire  20 , therefore, causes the maintenance termination unit  22  to connect the local loop to the customer&#39;s premise wiring  14 .  
         [0026]    Polarity is also used to isolate the customer&#39;s premise wiring  14 . FIG. 4 shows the polarity of the ring wire  18  causing positive charges to gather at the first terminal  24 . These positive charges repel the positive charges gathered at the north pole  34  of the magnet  32 . The corresponding polarity of the tip wire  20  causes negative charges to gather at the second terminal  26 , and these negative charges repel the negative charges gathered at the south pole  36 . FIG. 4, then, shows that this repelling force causes the magnet  32  to move and disconnect the first terminal  24 , and thus the ring wire  18 , from the third terminal  28 . This repelling force, likewise, causes the magnet  32  to move and disconnect the second terminal  26 , and thus the tip wire  20 , from the fourth terminal  30 . The polarity of the ring wire  18  and the tip wire  20 , therefore, causes the maintenance termination unit  22  to isolate the local loop to the customer&#39;s premise wiring  14 .  
         [0027]    [0027]FIG. 5 is a schematic showing a means of storing a charge. This means of storing a charge helps maintain an isolation between the customer&#39;s premise wiring  14  and the local loop (shown as reference numeral  16  in FIGS. 1 and 2). A reversed polarity condition, as described above, activates the maintenance termination unit  22 . Once the maintenance termination unit  22  isolates the customer&#39;s premise wiring  14  from the local loop, polarity may again be switched. The ring wire  18  would return to a normally positive voltage compared to the tip wire  20 . Even though the ring wire  18  now has a positive voltage, the means of storing a charge helps maintain the isolation between the customer&#39;s premise wiring  14  and the local loop. The means of storing a charge acts to create a voltage differential between the first terminal  24  and the second terminal  26 . The means of storing a charge may additionally, or alternatively, act to create a voltage differential between the third terminal  28  and the fourth terminal  30 .  
         [0028]    As FIG. 5 shows, the means of storing a charge may be a capacitor  38 . The capacitor  38  is charged when polarity is initially reversed; that is, when polarity changes, thus moving the magnet  32  to isolate the customer&#39;s premises, the capacitor  38  charges while polarity is reversed. When polarity reverts to a conventional +48 volts on the ring wire  18 , the capacitor  38 , as FIG. 5 shows, maintains a voltage differential between the third terminal  28  and the fourth terminal  30 . The capacitor  38  maintains a gathering of positive charges at the third terminal  28 . These positive charges repel the positive charges gathered at the north pole  34  of the magnet  32 . The capacitor  38  also maintains a gathering of negative charges at the fourth terminal  30 , and these negative charges repel the negative charges gathered at the south pole  36 . The capacitor  38 , then, maintains the repelling force that causes the magnet  32  to move and to respectively disconnect terminals  24  and  26  from terminals  28  and  30 .  
         [0029]    The capacitor  38  maintains this isolation for a predefined length of time. The capacitance C of the capacitor  38  can be chosen to maintain a voltage for any amount of time, from milliseconds to hours, according to the well-known equation  
         v        (   t   )       =       1   C            ∫   0   t                    (   x   )                            x     .                                 
 
         [0030]    The capacitor  38 , however, preferably only maintains a voltage for a predefined, finite amount of time, during which time the remote test is performed. The capacitor  38 , for example, preferably maintains a voltage (charge) for an amount of time not exceeding about a minute. This “test window” should be ample time for a remote test of the local loop. When the test window expires, the maintenance termination unit  22  restores a connection between the local loop and the customer&#39;s premise wiring  14 .  
         [0031]    The maintenance termination unit  22  may also utilize an alternating current signal. Although the ring wire  18  usually carries a constant, DC voltage of +48 volts, the quick reversal in polarity creates a time-varying current that allows the capacitor  38  to charge. The reversal in polarity, however, could be accompanied by an alternating current (AC) burst signal. This AC burst signal would be sent along the local loop to the maintenance termination unit  22 . Because the AC burst signal is time-varying, and biased by the reversed 48 volts, the AC burst signal ensures the capacitor  38  is charged. The AC burst signal could precede, or follow, the reversal of polarity. The duration of the AC burst signal, and its peak-to-peak magnitude, are chosen to ensure the capacitor  38  is adequately charged. Once the capacitor  38  is charged, by the reversal of polarity and/or by the AC burst signal, the local loop is remotely tested. Because the customer&#39;s premise wiring  14  is isolated from the local loop, if trouble is detected, that trouble lies within the local loop.  
         [0032]    [0032]FIG. 6 is a flowchart showing one method of remotely testing a local loop for trouble. Signals are communicated from a central office along a local loop (Block  40 ). The local loop comprises a ring wire and a tip wire. Polarity is reversed between the ring wire and the tip wire (Block  42 ). A time-varying signal is sent along the local loop (Block  44 ). A customer&#39;s wiring is isolated from the local loop for a predefined amount of time (Block  46 ), and a test of the local loop is remotely performed (Block  48 ) while the customer&#39;s wiring is separated.  
         [0033]    [0033]FIG. 7 is a flowchart showing another method of remotely testing a local loop for trouble. Signals are communicated from a central office along a local loop (Block  50 ). The local loop comprises a ring wire and a tip wire. Polarity is reversed between the ring wire and the tip wire (Block  52 ). A time-varying AC signal is sent along the local loop (Block  54 ). A magnet is utilized to isolate a customer&#39;s wiring from the local loop for a predefined amount of time (Block  56 ). The reversal in polarity may attract the magnet (Block  58 ) or repel the magnet (Block  60 ). Polarity may be again reversed (Block  62 ), returning the ring wire to a positive voltage compared with the tip wire. A test of the local loop is then remotely performed (Block  64 ) while the customer&#39;s wiring is separated. While the present invention has been described with respect to various features, aspects, and embodiments, those skilled and unskilled in the art will recognize the invention is not so limited. Other variations, modifications, and alternative embodiments may be made without departing from the spirit and scope of the present invention.