Abstract:
A cost-effective technique for inserting a switching module into a line pair of a local telecommunications network is disclosed. In particular, the illustrative embodiment does not replace a punch-down block at a cross-connect, but rather inserts the switching module between the modular connectors that are usually co-located with the punch-down block and that connect the cable pairs to the punch-down block. In other words, the illustrative embodiment provides for a technician to disconnect a pair of modular connectors and to insert a switching module between them, wherein the switching modules inputs and outputs are provided via modular connectors.

Description:
FIELD OF THE INVENTION 
   The present invention relates to telecommunications in general and, more particularly, to an apparatus and method to improve the reliability of, and provide efficient maintenance for, telephone outside plant. 
   BACKGROUND OF THE INVENTION 
     FIG. 1  depicts a schematic diagram of local telecommunication network  100  in the prior art, in which the network provides telecommunication service to a number of subscribers that are situated within a geographic region. The core of local telecommunication network  100  is central office  101 , which comprises at least one switch. The switch or switches at central office  101  connect subscribers in a given area to the public switched telephone network. The public switched telephone network is not actually part of any local network, but is a collection of switches and specific paths called “trunks” that connect the switches. Typically, the switch at central office  101  is connected to the rest of local telecommunication network  100  through a main distributing frame (abbreviated MDF) to large-capacity cable forming the first transmission facility, commonly referred to as F 1  cable, at the exchange end of what is known as the local loop. 
   Typically, F 1  cable  111  contains 1200 cable pairs. The wire pairs, or line pairs, are made of copper and are twisted to minimize crosstalk. F 1  cable  111  is connected to cross-connect  103 - 1 . As defined in Newton&#39;s Telecom Dictionary, 17 th  Edition, a “cross-connect” is defined as a connection scheme between cabling runs, subsystems, and equipment using patch cords or jumpers that attach to connecting hardware on each end. At cross-connect  103 - 1 , those 1200 pairs are separated into smaller units, with two cables containing 500 pairs each, represented by cable  112  and  113 , and two other cables containing 100 pairs each, represented by cable  114  and  115 . F 2  cable  115  is connected to cross-connect  103 - 2 . At cross-connect  103 - 2 , those 100 pairs are separated into smaller units, with one cable containing 75 pairs, represented by cable  116 , and one other cable containing 25 pairs, represented by cable  117 . The final run, F 3  cable  117 , is connected to cross-connect  103 - 3 . In other local networks, possibly different numbers of cross-connects and cables are used. It is common for facilities numbering as high as F 8  to be used, even though illustrative local telecommunication network  100  uses only F 1  through F 3 . 
   Also constituting local telecommunication network  100  are telephone  104 - 1  through  104 - 25 , served by line pairs connected to cross-connect  103 - 3 . A cross-connect, such as cross-connect  103 - 3 , that is used to split out line pairs for individual telephones is also referred to as a drop service terminal or, simply, a service terminal. The telephone terminals are at the subscriber end of the local loop. A specific loop path spanning local telecommunication network  100  serves each subscriber. 
   Note that cable  112 ,  113 ,  114 , and  116  are connected to other cross-connects not shown in  FIG. 1 . It is possible that each active line pair within each of cable  112 ,  113 ,  114 , and  116  terminates eventually at a telephone terminal at the subscriber end of the particular local loop served by the cable. 
   The segment of a local loop between the central office and the first outside plant node, that node being represented in  FIG. 1  by cross-connect  103 - 1 , can comprise a physical pair of wires or can comprise a virtual feeder pair in the form of a digital loop carrier (DLC) time slot. Similarly, just as F 1  cable  111  can use virtual pairs, subsequent distribution legs (i.e., F 2  cable  115  and F 3  cable  117 ) can, use virtual pairs as well. The segments of local loop extending beyond cross-connect  103 - 1  are generally called distribution pairs. The last segment of local loop before each of telephone  104 - 1  through  104 - 25  is called a drop pair, or simply a drop. 
   Differing terms are sometimes used to describe cross-connects, such as feeder-distribution interface (FDI), remote terminal, and serving terminal, depending on where the cross-connect is situated in the local loop and the format of the signal the cross-connect handles. In all cases, cross-connects are the same in that they are demarcation points at which one transmission segment ends and another begins. Furthermore, at a most fundamental, conceptual level, cross-connects are the same. Such a logical extension of concepts should also be extended to varying arrangements in which the virtual feeder or distribution (for example, in the form of a digital loop carrier or a fiber) may be used not only for the F 1  cable, but for any facility or leg of a subscriber loop. 
   An efficient process of maintenance for local loops depends on the ability to test subscriber lines at any time without dispatching technicians. Typically the biggest source of expense is the labor cost associated with dispatching into the field to manually make cross-connections in the FDIs and remote and serving terminals. Worse yet, the work typically performed for a new line or maintenance change in the local loop plant requires line rearrangements. For a significant number of those rearrangements, errors will almost inevitably occur, either in the rearrangement itself or in one or more administrative database entries made due to those changes. Error creation introduces even more expense to correct the errors. 
   Regardless of the subscriber service, the ability to test at the time a customer calls to report a trouble or at any time is crucial for efficient maintenance. These tests must be performed quickly and ideally without dispatching a field technician. Speed is important so that at least some common problems can be diagnosed (and ideally repaired) while the subscriber is on the phone with a repair service agent. For example, a common problem occurs when a subscriber leaves his phone off-hook. This can occur when a subscriber with two phones connected to one line leaves one phone off-hook during a conversation to pick up his other phone and forgets to hang up the phone used originally. After some time of sounding the receiver off-hook signal, the serving central office times out and essentially disconnects the subscriber&#39;s line. When the subscriber later tries to make a call using the second phone that was properly hung up, unaware that the first line is still off-hook, the phone line is perceived as broken. This subscriber might then call customer service complaining that he is unable make a call. Test equipment currently in common use (e.g., the Mechanized Loop Test, or MLT, provided by Lucent Technologies to Bell operating companies, etc.) can detect the receiver-off-hook condition and the repair agent can remind the subscriber to check his other phone lines, knowing that receiver-off-hook is likely the problem. On such a call, no technician is dispatched; indeed, even the process of recording this trouble call can be skipped, although it is likely recorded for statistical purposes. As the preceding description shows, this trouble call is efficiently handled because test equipment, which is sophisticated enough to detect the receiver-off-hook condition, can be switched onto any subscriber&#39;s line quickly and run tests while the subscriber is talking with a customer service agent. Such efficiency is vital to modern telephone system operations; service would no longer be affordable if such capabilities were unavailable. 
   Issues such as the one described above concern both testing (particularly centralized testing) and maintenance, as these two activities are inextricably intertwined within many telephone company operations. 
   Often, the problem the subscriber is having with her phone service is not as straightforward as, for example, a phone line being off-hook. There is occasionally something wrong with the local loop between the central office and the subscriber&#39;s telephone. While there are some repairs that can be effected remotely, usually the technician has to diagnose the problem, determine where along the line the problem is, and repair the problem (e.g., a physical break in the line, etc.). If the problem turns out to be a broken line, the technician can mend the actual break in the wire or can reconfigure the local loop so that the subscriber is assigned a new physical line. Ideally, only the specific segment between cross-connects or splices to where the problem has been localized is swapped out. 
   One issue with swapping out a line, for testing or re-provisioning purposes, is that the technician has to visit at least two places along the local loop for the subscriber. One place is the cross-connect or splice on the exchange side of the impairment, and the other place is the cross-connect or splice on the subscriber side of the impairment. The technician typically has to access a manual cross-connect box, depicted in  FIG. 2  of the prior art. This box typically comprises mechanical connecting terminals called punchdown blocks. Line pairs on the exchange side are mechanically connected to one set of punchdown blocks, whereas line pairs on the subscriber side are mechanically connected to a second set of punchdown blocks. Each exchange-side line pair is then connected to the corresponding subscriber-side line pair by a jumper wire pair running from one punchdown block to the other. There is a plurality of exchange-side line pairs and a plurality of subscriber-side line pairs terminating at the box. Note that there are typically more line pairs provisioned through manual cross-connect panel  201  than are presently in use. The additional line pairs allow for growth and, in the example, for swapping out when needed. Furthermore, the number of exchange-side line pairs (i.e.,  211 - 1  through  211 -M) and subscriber-side line pairs (i.e.,  212 - 1  through  212 -N) can be different from each other (i.e., M and N can have different values). 
   Manual cross-connect boxes are relatively inexpensive because they are passive devices requiring no power source. They are easy to use, requiring relatively little training on the part of the technician. Furthermore, the practice of using jumper wires to connect one punchdown block to another significantly reduces confusion as different line pair combinations get rewired over time. 
   Disadvantageously, manual cross-connect boxes cannot be reconfigured remotely, requiring trips by the technician to each cross-connect that has to be reconfigured. Because of this inconvenience, tests and provisioning that ordinarily would be tried are possibly infeasible. Furthermore, a problem with reconfiguring manual cross-connect panel  201  is the possibility of technician error. Typically, there are dozens, if not hundreds, of line pairs at a cross-connect. Even though the wires are color-coded, it is possible that the technician swaps in the wrong wire pair or does not make a solid, durable splice. Again, consider that when swapping in a new line pair, the technician has a chance to make an error in two places: at the exchange-side of the impairment and at the subscriber-side of the impairment. 
     FIG. 3  depicts automated cross-connect matrix  301  of the prior art, which joins a plurality of exchange-side line pairs (i.e.,  311 - 1  through  311 -M) and a plurality of subscriber-side line pairs (i.e.,  312 - 1  through  312 -N). Sanford et. al. in U.S. Pat. No. 5,912,960 teach an apparatus and method that can be used to make an automated cross-connect. As in the case of manual cross-connect panel  201 , there are typically more line pairs provisioned through automated cross-connect matrix  301  than are presently in use. The additional line pairs allow for growth and, in the example, for swapping out when needed. Furthermore, the number of exchange-side line pairs and subscriber-side line pairs can be different from each other (i.e., M and N can have different values). 
   Automated cross-connect matrix  301  represents an improvement over manual cross-connect  201 , in that most reconfigurations can be performed without a technician having to make a trip or two to the local loop. Automated cross-connect matrix  301  is controlled from presumably a convenient location (e.g., the serving central office, etc.), so a swapping of one line pair for another can be performed conveniently in less time, probably with fewer errors and at lower labor cost. 
   However, automated cross-connect matrix  301  has some disadvantages. As a new cross-connect serving a new group of subscribers (e.g., new housing development, new office park, etc.), automated cross-connect matrix  301  can represent a significant initial investment cost. The cross-connect can conceivably join any exchange-side line pair with any subscriber-side line pair, requiring a relay or switch for each pair combination, making automated cross-connect matrix  301  more expensive than manual cross-connect panel  201 . As a, replacement cross-connect to an existing manual cross-connect, installing automated cross-connect matrix  301  can result in significant downtime. Line pairs serving subscribers have to be disconnected from the existing cross-connect, the existing cross-connect has to be removed, the new cross-connect has to be installed, and the line pairs have to be reconnected into the new cross-connect. Finally, it is often sufficient to automate a portion of the line pairs at a cross-connect, such that installing automated cross-connect matrix  301  would be excessive for serving the actual need. 
   There exists a need for a practical automating of re-mapping the pair connectivity of some or all of the line pairs within a local telecommunication network. Specifically, a need exists for the convenience, speed, reduced likelihood of errors associated with automating line pairs at a cross-connect in a local loop without the expense, downtime, and lack of scalability of the automated solutions in the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention provides a cost-effective technique for inserting a switching module into a line pair of a local telecommunications network. In particular, the illustrative embodiment does not replace a punch-down block at a cross-connect, but rather inserts the switching module between the ubiquitous modular connectors that are usually co-located with the punch-down block and that connect the cable pairs to the punch-down block. In other words, the illustrative embodiment provides for a technician to disconnect a pair of modular connectors and to insert a switching module between them, wherein the switching modules inputs and outputs are provided via modular connectors. 
   This augments the cross-connect and overall local telecommunication network by providing a technician convenience, speed, and reduced likelihood of errors in reconfiguring line pairs within the local telecommunication network. 
   A plurality of switching modules can be introduced at a manual cross-connect to introduce a more scalable and more economical switching capability than is typically achieved by swapping out the manual cross-connect for an automated cross-connect. The present invention allows the network planner to decide to augment one pair unit, some pair units, or all pair units present at a cross-connect. 
   The illustrative embodiment of the present invention comprises: a first N-pair modular connector for joining a first plurality of line pairs to a corresponding plurality of exchange-side line pairs; a second N-pair modular connector for joining a second plurality of line pairs to a corresponding plurality of subscriber-side line pairs; a controller responsive to a first control signal received through said first plurality of line pairs for establishing switching configurations; and a switch for configuring a specified line pair within said first plurality of line pairs relative to another specified line pair within said second plurality of line pairs based on stimuli from said controller, wherein said first N-pair modular connector mates with at least one of an MS-squared connector, a 710 connector, and a single-side mechanical copper connector, and N is a positive integer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts a block diagram of local telecommunication network  100  in accordance with the prior art. 
       FIG. 2  depicts a block diagram of a manual cross-connect in accordance with the prior art. 
       FIG. 3  depicts a block diagram of an automated cross-connect in accordance with the prior art. 
       FIG. 4  depicts a block diagram of a cross-connect with pair unit connectors. 
       FIG. 5  depicts a block diagram of the first illustrative embodiment of the present invention. 
       FIG. 6  depicts a block diagram of switch housing  501 -j, as shown in  FIG. 5 , in accordance with the first illustrative embodiment of the present invention. 
       FIG. 7A  depicts a block diagram of switch  601 , as shown in  FIG. 6 , in accordance with the first mode of operation of the present invention. 
       FIG. 7B  depicts a block diagram of switch  601 , as shown in  FIG. 6 , in accordance with the second mode of operation of the present invention. 
       FIG. 7C  depicts a block diagram of switch  601 , as shown in  FIG. 6 , in accordance with the third mode of operation of the present invention. 
       FIG. 8  depicts a block diagram of the second illustrative embodiment of the present invention. 
       FIG. 9  depicts a block diagram of switch housing  801 -j, as shown in  FIG. 8 , in accordance with the second illustrative embodiment of the present invention. 
       FIG. 10  depicts a block diagram of switch  901 , as shown in  FIG. 9 , in accordance with the fourth mode of operation of the present invention. 
       FIG. 11  depicts a block diagram of loop segment  1100  in accordance with the third illustrative embodiment of the present invention. 
       FIG. 12  depicts a block diagram of loop segment  1200  in accordance with the fourth illustrative embodiment of the present invention. 
       FIG. 13  depicts a flowchart of the tasks related to installing switching module  500 -j, as shown in  FIG. 5 . 
   

   DETAILED DESCRIPTION 
     FIG. 4  depicts a block diagram of the salient components of cross-connect  400  in accordance with the illustrative embodiment. When cross-connect  400  is outdoors, it typically comprises a cabinet (not shown) that is used to house equipment that joins a plurality of exchange-side line pairs to a plurality of subscriber-side line pairs. In contrast, when cross-connect  400  is indoors, it often does not comprise a cabinet, but appears on a wall within a wiring closet in a building. 
   In either case, cross-connect  400  also comprises connection media, in this case cross-connect panel  401 , which in turn comprises one or more punch-down blocks and jumper wires. It is well-known to those skilled in the art how to make and use cross-connect  400 . Although a manual cross-connect is shown in  FIG. 4 , it will be clear to those skilled in the art, after reading this specification, that cross-connect  400  can also comprise an automated cross-connect. 
   In accordance with the illustrative embodiment, there are more line pairs provisioned through cross-connect  400  than are intended to be immediately in use. The additional line pairs allow for growth and for swapping out defective line pairs when necessary. Furthermore, it will be clear to those skilled in the art that the number of exchange-side line pairs and the number of subscriber-side line pairs can be different. 
   The line pairs terminating at a cross-connect are grouped together hierarchically. A clustering of individual line pairs forms a pair unit. There are 25 line pairs per pair unit. It will be clear to those skilled in the art, however, how to make and use pair units comprising a different number of line pairs than 25. For example, other common groupings are 5 line pairs per pair unit and 10 line pairs per pair unit. Pair unit  411 -j, for j=1 to P, exists on the exchange-side of cross-connect cabinet  401 . Pair unit  412 -k, for k=1 to Q, exists on the subscriber-side of cross-connect cabinet  401 . It will be clear to those skilled in the art how to configure cross-connect  400  with a different number of pair units on the exchange side than on the subscriber side (i.e., P can, but does not necessarily need to equal Q). 
   Cross-connect panel  401  is the means by which an exchange-side pair is joined to a subscriber-side pair. As shown in  FIG. 4 , pair unit  411 - 1  is connected by cross-connect cabinet  401  to pair unit  412 - 2 . Similarly, pair unit  411 - 2  is connected by cross-connect  401  to pair unit  412 -Q, and pair unit  411 -P is connected by cross-connect  401  to pair unit  412 - 1 . All active line pairs on the exchange side are wired to active line pairs on the subscriber side. 
   Pair unit  411 -j is electrically connected within cross-connect  400  to pair unit connector  402 - 2 -j and to cross-connect panel,  401 , for j=1 to P. Each pair unit connector  402 - 2 -j, in turn, is attached to pair unit connector  402 - 1 -j, which is electrically connected to a corresponding exchange-side pair unit. 
   On the subscriber side, pair unit  412 -k is electrically connected within cross-connect  400  to pair unit connector  403 - 1 -k and to cross-connect panel  401 , for j=1 to Q. Each pair unit connector  403 - 1 -k, in turn, is attached to pair unit connector  403 - 2 -k, which is electrically connected to a corresponding subscriber-side pair unit. 
   In the example of a 25-pair pair unit, each of connector  402 - 1 -j,  402 - 2 -j,  403 - 1 -k, and  403 - 2 -k is generically referred to as a 25-pair modular connector. There are a few connector types that have become the industry standards. One type is the Dynatel 710 (pronounced “Dynatel seven-ten”), also known as 710, designed by Dynatel. A second type is the MS 2  (pronounced “MS-squared”), also known as MS2, made by 3M Corporation. A third type is the single-side mechanical copper connector, made by AMP and Scotchlok. A modular connector pair (e.g.,  402 - 1 -i and  402 - 2 -i, etc.) comprises a male connector and a female connector that are designed to fit together to form a secure mechanical and electrical connection. The modular connectors are present for pair units within cross-connect cabinet  103 -i. 
     FIG. 5  depicts a block diagram of the salient components of the first illustrative embodiment of the present invention. Switching module  500 -j comprises switch housing  501 -j, connector  502 - 1 -j, and connector  502 - 2 -j. Switch housing  501 -j is where the switching function resides, which is electrically connected to connector  502 - 1 -j and  502 - 2 -j in well-known fashion via pair unit  511 -j and  512 -j, respectively, and will be discussed later. Connector  502 - 1 -j is designed to attach to connector  402 - 1 -j in a male/female configuration as described earlier. Connector  502 - 2 -j is designed to attach to connector  402 - 2 -j in a male/female configuration as described earlier. Switching module  500 -j handles a cable pair unit from each of the two sides. It will be clear to those skilled in the art how to make and use suitable connectors, such as the connector models identified earlier. It will be also clear to those skilled in the art that switching module  500 -j can be used on the subscriber side of a cross-connect only, on the exchange side of a cross-connect only, or on both sides of a cross-connect. Furthermore, it will be clear to those skilled in the art that switching module  500 -j can be used for some pair units and not for others associated with cross-connect  400 . 
     FIG. 6  depicts a block diagram of the salient components of switch housing  501 -j, which comprises switch  601  and controller  602 . Line pairs  611 -g, for g=1 to R, constitute pair unit  511 -j. Line pairs  612 -h, for h=1 to S, constitute pair unit  512 -j. Switch  601  serves to establish the correct loop path mapping between exchange-side line pairs  611 -g, for g=1 to R, and line pairs to subscribers  612 -h, for h=1 to S. Although, R and S are equal in the illustrative embodiment, it will be clear to those skilled in the art how to make and use a switch with a different number of lines on each terminating end of the switch (i.e., R≠S). 
   Switch  601  can control all of the line pairs or merely a non-empty, proper subset of the line pairs. Switch  601  can provide connectivity between exchange-side line pairs and subscriber-side line pairs in every combination, or switch  601  can provide a non-exhaustive set of connectivity, depending on what the particular application requires. Switch  601  can be built based on micro-electromechanical system (i.e., MEMS) technology or other technology. It will be clear to those skilled in the art how to make and use switch  601 , controlled by controller  602 . 
   Controller  602  accepts control signals from the technician or from technician-controlled operations, administration, maintenance, and provisioning (OAM&amp;P) equipment. The control signals are used to properly configure switch  601  via path  613 . The technician and OAM&amp;P equipment can be situated at a convenient, centralized location within or near local telecommunication network  100  (e.g., near central office  101 , etc.). The OAM&amp;P equipment can send control signals along a dedicated line pair (e.g.,  611 - 1 , etc.) that controller  602  knows is used for control signaling. Controller  602  is configured to monitor via path  614  the control signal traffic on the dedicated control signaling line pair. It will be clear to those skilled in the art how to create and use control signaling to be used by controller  602 . It will be also clear to those skilled in the art how to provision a specific line pair or pairs to be used for carrying control signals and how to monitor for control signals. Alternatively, controller  602  can receive control signals from a dedicated path other than line pair  611 -g. Path  615  represents a dedicated path for control signaling. Path  615  can be implemented with an interface such as RS-232. It will be clear to those skilled in the art how to make and use a separate path for carrying control signals. 
   Controller  602  can also pass control signals further along local telecommunication network  100 . This is necessary if the control signal intercepted by controller  602  is not intended for switch  601 . Another scenario is where controller  602  needs to coordinate an action with one or more additional switching modules. The control signal can be passed along via path  616  using a line pair dedicated for control signaling purposes (e.g., line pair  612 - 1 , etc.). Alternatively, the control signal can be passed along a separate control path, depicted in  FIG. 6  as path  617 . It will be also clear to those skilled in the art how to provision a specific line pair or pairs to be used for forwarding control signals. It will be clear to those skilled in the art how to make and use a separate control path for passing control signals. 
   Switch  601  and Controller  602  are nominally line-powered by one or more line pairs on the exchange side based on −48V DC  voltage from central office  101 . It will be clear to those skilled in the art how to line-power switch  601  and controller  602 . Alternatively, switch  601  and controller  602  can draw power from a power supply local to host cross-connect  400 . It will be clear to those skilled in the art how to power switch  601  and controller  602  locally. 
     FIG. 7A  depicts the first mode of operation of the present invention. In the drawing, switch  601  initially has established a connection as shown by the dashed line between exchange-side line pair  611 - 1  and subscriber-side line pair  612 - 1 . Upon receiving a command within a control signal, switch  601  reconfigures to connect line pair  611 - 1  to  612 - 2 . This can apply to a situation where a technician has determined that line pair  612 - 1  is faulty and that  612 - 2  will be the line pair associated with the subscriber going forward. 
     FIG. 7B  depicts the second mode of operation of the present invention. In the drawing, switch  601  initially has established a connection as shown by the dashed line between exchange-side line pair  611 - 1  and subscriber-side line pair  612 - 1 . Upon receiving a command within a control signal, switch  601  opens the connection, essentially leaving line pair  611 - 1  not connected to anything (i.e., open-circuited). This can apply to a situation where a technician suspects that line pair  612 - 1  is short-circuited to itself. If the measured impedance on line  611 - 1  changes from a low or zero value to the correct open circuit value, this test will confirm or strongly suggest that line pair  612 - 1  is shorted. 
     FIG. 7C  depicts the third mode of operation of the present invention. In the drawing, switch  601  initially has established a connection as shown by the dashed line between exchange-side line pair  611 - 1  and subscriber-side line pair  612 - 1 . Upon receiving a command within a control signal, switch  601  crosses the connection from exchange-side line pair  611 - 1  back to another exchange-side line pair, line pair  611 -R. Such a reconfiguring is useful for testing the overall characteristics of line pair  611 - 1  all the way back to the test equipment (e.g., equipment at central office  101 , etc.). 
     FIG. 8  depicts the second illustrative embodiment of the present invention. Switching module  800 -j comprises switch housing  801 -j, connector  802 - 1 -j, connector  802 - 2 -j, and connector  802 - 3 -j. Switch housing  801 -j is where the switching function resides, which is electrically connected to connector  802 - 1 -j,  802 - 2 -j, and  802 - 3 -j in well-known fashion via pair unit  811 -j,  812 -j, and  813 -j, respectively, and will be discussed later. Connector  802 - 1 -j is designed to attach to connector  402 - 1 -j. Connector  802 - 2 -j is designed to attach to connector  402 - 2 -j. Connector  802 - 3 -j is designed to attach to connector  821 -j, which is associated with a technician-defined or network planner-defined auxiliary path (i.e., the “auxiliary side”) in local telecommunication network  100 . Switching module  800 -j handles a cable pair unit from each of the three paths. It will be clear to those skilled in the art how to make and use suitable connectors, such as the connector models identified earlier. It will be also clear to those skilled in the art that switching module  800 -j can be used on the subscriber side of a cross-connect only, on the exchange side of a cross-connect only, or on both sides of a cross-connect. Furthermore, it will be clear to those skilled in the art that switching module  800 -j can be used for some pair units and not for others associated with cross-connect  400 . 
     FIG. 9  depicts switch housing  801 -j comprising switch  901  and controller  902 . Line pairs  911 -g, for g=1 to R, constitute pair unit  811 -j. Line pairs  912 -h, for h=1 to S, constitute pair unit  812 -j. Line pairs  913 -l, for l=1 to T, constitute pair unit  813 -j. Switch  901  serves to establish the correct loop path mapping between exchange-side line pairs  911 -g, for g=1 to R, and line pairs to subscribers  912 -h, for h=1 to S. Furthermore, switch  901  provides connectivity between the third pair unit comprising line pairs  913 -l, for l=1 to T, and the first two line pair units. Although R, S, and T are equal in the illustrative embodiment, it will be clear to those skilled in the art how to make and use a switch with a different number of lines on each terminating end of the switch (i.e., R≠S≠T). Switch  901  can control all of the line pairs or merely a non-empty, proper subset of the line pairs. Switch  901  can provide connectivity between exchange-side line pairs and subscriber-side line pairs and auxiliary-side line pairs in every combination, or switch  901  can provide a non-exhaustive set of connectivity, depending on what the particular application requires. Switch  901  can be built based on micro-electromechanical system (i.e., MEMS) technology or other technology. It will be clear to those skilled in the art how to make and use switch  901 , controlled by controller  902 . 
   Controller  902  accepts control signals from the technician or from technician-controlled operations, administration, maintenance, and provisioning (OAM&amp;P) equipment. The control signals are used to properly configure switch  901  via path  914 . The technician and OAM&amp;P equipment are presumably situated at a convenient, centralized location within or near local telecommunication network  100  (e.g., near central office  101 , etc.). The OAM&amp;P equipment can send control signals along a dedicated line pair (e.g.,  911 - 1 , etc.) that controller  902  knows is used for control signaling. Controller  902  is configured to monitor via path  915  the control signal traffic on the dedicated control signaling line pair. It will be clear to those skilled in the art how to create and use control signaling to be used by controller  902 . It will be also clear to those skilled in the art how to provision a specific line pair or pairs to be used for carrying control signals and how to monitor for control signals. Alternatively, controller  902  can receive control signals from a dedicated path other than line pair  911 -g. Path  916  represents a dedicated path for control signaling. Path  916  can be implemented with an interface such as RS-232. It will be clear to those skilled in the art how to make and use a separate path for carrying control signals. 
   Controller  902  can also pass control signals further along local telecommunication network  100 . This is necessary if the control signal intercepted by controller  902  is not intended for switch  901 . Another scenario is where controller  902  needs to coordinate an action with one or more additional switching modules. The control signal can be passed along via path  917  using an exchange side line pair dedicated for control signaling purposes (e.g., line pair  912 - 1 , etc.) or via path  918  using an auxiliary-side line pair dedicated for control signaling purposes (e.g., line pair  913 - 1 , etc.). Alternatively, the control signal can be passed along a separate control path, depicted in  FIG. 9  as path  919 . It will be also clear to those skilled in the art how to provision a specific line pair or pairs to be used for forwarding control signals. It will be clear to those skilled in the art how to make and use a separate control path for passing control signals. 
   Switch  901  and Controller  902  are nominally line-powered by one or more line pairs on the exchange side based on −48V DC  voltage from central office  101 . It will be clear to those skilled in the art how to line-power switch  901  and controller  902 . Alternatively, switch  901  and controller  902  can draw power from a power supply local to host cross-connect  400 . It will be clear to those skilled in the art how to power switch  901  and controller  902  locally. 
     FIG. 10  depicts the fourth mode of operation of the present invention. In the drawing, switch  901  initially has established a connection as shown by the dashed line between exchange-side line pair  911 - 1  and subscriber-side line pair  912 - 1 . Upon receiving a command within a control signal, switch  901  reconfigures to connect line pair  911 - 1  to  913 - 2 , an auxiliary-side line pair. This can apply to a situation where it is desirable to bypass line  912 - 1  by using other transmission lines (e.g., testing equipment, cascaded switches, etc.), which will be discussed later. 
     FIG. 11  depicts loop segment  1100  in an illustrative example, in which several switching modules are co-located with a plurality of cross-connects. Specifically, cross-connect  1101  hosts switching module  1102 - 1  and  1102 - 2 . Cross-connect  1103  hosts switching module  1104 - 1  and  1104 - 2 . There are multiple feeder cable runs spanning loop segment  1100 . The first feeder run comprises cable  1111 ,  1112 ,  1113 ,  1114 , and  1115 , and provides a plurality of loop paths. The second feeder run comprises cable  1116 ,  1117 ,  1118 ,  1119 , and  1120 , and provides a plurality of loop paths. The span between cross-connect  1101  and cross-connect  1103  runs through a built up geographic area with other infrastructure present. It is possible that either cable  1113  or cable  1118  might be inadvertently damaged (e.g., by a backhoe digging a hole in the vicinity, etc.) Cable run diversity is typically used to divide up loop paths across multiple cable runs spanning the same area to guard against mishaps such as a cable being damaged. A number of spare line pairs are provided along each run to be activated if need. Therefore, there are loop paths running through cable  1111 ,  1112 ,  1118  (i.e., as opposed to  1113 ),  1114 , and  1115 . Likewise, there are loop paths running through  1116 ,  1117 ,  1113  (i.e., as opposed to  1118 ),  1119 , and  1120 . Cable run diversity is achieved by having the multiple cables between two end points running in different paths between the two end points. 
   In an illustrative example, suppose that cable  1113  is severed by a backhoe. The loop paths previously served by line pairs running through cable  1113  have to be reconfigured to use cable  1118 . Without switching modules in place, a technician would have to manually reconfigure cross-connect  1101  and  1103  to establish loop paths through cable  1118 . However, with switching module  1102 - 1  and  1104 - 1  in place, the reconfiguring of loop paths can be done at a convenient location and in a coordinated fashion, saving time and money, as well as minimizing error. Switch module  1102 - 1  is responsive to a control signal provided by cable  1111  from the provisioning equipment at central office  101 . Switch module  1104 - 1  is responsive to a corresponding control signal provided by cable  1114 . Control signal diversity through the span between cross-connect  1101  and  1103  is achieved by provisioning a line pair through each of cable  1113  and  1118  for control signal purposes. 
   In the event that cable  1118  were cut instead of cable  1113 , switching module  1102 - 2  and  1104 - 2  would be used to reconfigure the loop paths. Switch module  1102 - 2  is responsive to a control signal provided by cable  1116  or by path  1121  from the provisioning equipment at central office  101 . Switch module  1104 - 2  is responsive to a corresponding control signal provided by cable  1119  or by path  1122 . Control signal diversity through the span between cross-connect  1101  and  1103  is achieved by provisioning a line pair through each of cable  1113  and  1118  for control signal purposes. 
     FIG. 12  depicts loop segment  1200  in another illustrative example, in which several switching modules, switching module  1202 - 1 ,  1202 - 2 ,  1202 - 3 , and  1202 - 4  are connected to cross-connect  1201 . The switching modules in the illustrative example have been installed individually over time, although they could have been installed at the same time without making a difference in the illustrative example. At some point in time, presumably when it makes sense to do so economically, operationally, and technically, central switch  1203  can be installed at cross-connect  1201 . Central switch  1203  is networked into the array of switching modules associated with cross-connect  1201 . 
   One purpose of the configuration depicted by  FIG. 12  is to provide switching across pair units, as opposed to within each pair-unit. In an illustrative example, suppose that a line pair associated with exchange-side pair unit  1211 - 1  has to be connected to a line pair associated with subscriber-side pair unit  1212 - 4 . Central switch  1203  sends a control signal via path  1204  to switching module  1202 - 1 . Switching module  1202 - 1  then switches the exchange-side line pair of interest within pair unit  1211 - 1  to an unused pair unit associated with auxiliary-side pair unit  1213 - 1 . 
   Meanwhile, switching module  1202 - 1  sends a corresponding control signal to switching module  1202 - 4  via control path  1221 - 1 ,  1221 - 2 , and  1221 - 3 . Switching module  1202 - 4  then switches the subscriber-side line pair of interest within pair unit  1212 - 4  to an unused pair unit associated with auxiliary-side pair unit  1213 - 4 . 
   Central switch  1203  bridges the two selected auxiliary-side line pairs (i.e., associated with pair units  1213 - 1  and  1213 - 4 ) by establishing a connection between the selected line pairs. It will be clear to those skilled in the art how to make and use central switch  1203  for the purpose of reconfiguring local telecommunication system  100 . Note that central switch  1203  in tandem with a complement of switching modules does not have to provide connectivity across all pair units associated with cross-connect  1201 . Therefore, the configuration depicted in  FIG. 12  addresses the economic and scalability issues associated with upgrading cross-connect  1201 . 
     FIG. 13  depicts a flowchart of the tasks performed when introducing switching module  500 -j to a cross-connect environment. It will be clear to those skilled in the art which of the tasks depicted in  FIG. 13  can be performed simultaneously or in a different order than that depicted in  FIG. 13 . 
   At task  1301 , the installer disconnects the male connector from the female connector of a modular connector pair. The modular connector pair is associated with a one or more line pairs constituting a pair unit that is connected to a cross-connect. 
   At task  1302 , the installer connects the female connector of switching module  500 -j to the male connector of the original modular connector pair. 
   At task  1303 , the installer connects the male connector of switching module  500 -j to the female connector of the original modular connector pair. 
   At task  1304 , the installer configures switching module  500 -j for electrically connecting the line pairs associated with the male connector of the original modular connector pair to line pairs associated with the female connector of the original modular connector pair. Initially, each male connector line pair is electrically connected via switching module  500 -j to the corresponding female connector line pair to which the male connector line pair was originally connected prior to performing task  1301 . However, the technician can immediately reconfigure the line pairs as the technician deems necessary or advantageous. 
   It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.