FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to telecommunications equipment. More particularly, the present invention relates to systems for monitoring digital equipment.  
         BACKGROUND OF THE INVENTION  
         [0002]    A digital cross-connect system (DSX) provides a location for interconnecting two digital transmission paths. The apparatus for a DSX is located in one or more frames, or bays, usually in a telephone service provider&#39;s central office. The DSX apparatus also provides jack access to the transmission paths.  
           [0003]    DSX jacks are well known and typically include a plurality of bores sized for receiving plugs. A plurality of switches are provided adjacent the bores for contacting the plugs. The jacks are electrically connected to digital transmission lines, and are also electrically connected to a plurality of termination members used to cross-connect the jacks. By inserting plugs within the bores of the jacks, signals transmitted through the jacks can be interrupted or monitored.  
           [0004]    [0004]FIG. 1 schematically illustrates a DSX system that is an example of the type found at a telephone service provider&#39;s central office. The DSX system is shown including three DSX jacks  10   a ,  10   b  and  10   c.  Each DSX jack  10   a ,  10   b  and  10   c  is connected to a specific piece of digital equipment. For example, jack  10   a  is shown connected to digital switch  12 , jack  10   b  is shown connected to office repeater  14   a , and jack  10   c  is shown connected to office repeater  14   b . Each piece of digital equipment has a point at which a digital signal can enter, as well as a point at which the digital signal can exit. The jacks  10   a ,  10   b  and  10   c  each include OUT termination pins  16  and IN termination pins  18 . The DSX jacks  10   a ,  10   b  and  10   c  are connected to their corresponding pieces of digital equipment by connecting the OUT termination pins  16  to the signals exiting the equipment (i.e., going toward the DSX system) and the IN termination pins  18  to the signals entering the equipment (i.e., going away from the DSX system).  
           [0005]    Referring still to FIG. 1, jacks  10   a  and  10   b  are “cross-connected” to one another by semi-permanent connections. A “semi-permanent” connection is a connection that is more permanent than the connections provided by typical patch cords equipped with tip-and-ring plugs. Example semi-permanent connectors include co-axial connectors, wire wrap connectors, RJ-45 type connectors and insulation displacement connectors. The semi-permanent connections extend between cross-connect fields  19  of the jacks  10   a  and  10   b . For example, wires  20  connect OUT cross-connect pins of jack  10   a  to IN cross-connect pins of jack  10   b . Similarly, wires  21  connect IN cross-connect pins of jack  10   a  to OUT cross-connect pins of jack  10   b . The jacks  10   a  and  10   b  are preferably normally closed. Thus, in the absence of a plug inserted within either of the jacks  10   a  and  10   b , an interconnection is provided through the jacks  10   a  and  10   b  and between digital switch  12  and office repeater  14   a.    
           [0006]    The semi-permanent connection between the digital switch  12  and the office repeater  14   a  can be interrupted for diagnostic purposes by inserting patch cord plugs within the IN or OUT ports of the jacks  10   a  and  10   b . Likewise, patch cords can be used to interrupt the semi-permanent connection between the jacks  10   a  and  10   b  to provide connections with other pieces of digital equipment. For example, the digital switch  12  can be disconnected from the office repeater  14   a  and connected to the office repeater  14   b  through the use of patch cords  23 . The patch cords  23  include plugs that are inserted within the IN and OUT ports of the jack  10   a  and the IN and OUT ports of the jack  10   c . By inserting the plugs within the IN and OUT ports of the jack  10   a , the normally closed contacts are opened, thereby breaking the electrical connection with the office repeater  14   a  and initiating an electrical connection with office repeater  14   b.    
         SUMMARY OF THE INVENTION  
         [0007]    The present invention relates to devices for facilitating monitoring telecommunications signals.  
           [0008]    A variety of aspects of the invention are set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. The aspects of the invention relate to individual features as well as combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a schematic diagram of a prior art DSX system;  
         [0010]    [0010]FIG. 2 is a front perspective view of a monitor unit that is an embodiment of the present invention;  
         [0011]    [0011]FIG. 3 is a front view of the monitor unit of FIG. 2;  
         [0012]    [0012]FIG. 4 is a rear view of the monitor unit of FIG. 2;  
         [0013]    [0013]FIG. 5 is a side view of the monitor unit of FIG. 2;  
         [0014]    [0014]FIG. 6 is a circuit schematic for the monitor unit of FIG. 2; and  
         [0015]    [0015]FIG. 7 is a circuit schematic illustrating an example use for the monitor unit of FIG. 2. 
     
    
     DETAILED DESCRIPTION  
       [0016]    Reference will now be made in detail to exemplary aspects of the present invention that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
       a. General Description of Example Embodiment  
       [0017]    FIGS.  2 - 5  illustrate a monitor unit  30  that is an embodiment of the present invention. The monitor unit  30  includes a chassis  32  having a front side  31  (shown in FIG. 3) and a back side  33  (shown in FIG. 4). The monitor unit  30  also includes multiple rows of monitor jacks  34  that are accessible from the front side  31  of the chassis  32 . First and second groups  35 ,  37  of front connectors  38  (e.g., wire termination posts) are positioned on opposite sides of the monitor jacks  34 . The front connectors  38  allow the monitor unit  30  to be electrically coupled to other DSX jacks (such as jacks  501 ,  503  shown in FIG. 7) by semi-permanent connections. The monitor unit  30  also includes a plurality of rear connectors  40  (e.g., co-axial connectors) that are accessible from the back side  33  of the chassis  32 . The rear connectors  40  allow the monitor unit  30  to be electrically coupled to equipment  43  (see FIG. 7) such as testing or performance monitoring equipment.  
         [0018]    In use of the monitoring unit  30 , signals from a DSX circuit desired to be monitored (e.g., the circuit defined by jacks  501 ,  503  of FIG. 7) are input to the monitoring unit  30  through the front connectors  38 . From the front connectors  38 , the signals are carried through the chassis  32  to the rear connectors  40 . From the rear connectors  40 , the signals are carried to test/monitoring equipment such as the equipment  43  of FIG. 7. To perform dual monitoring of a signal, a tip-and-ring plug can be inserted into a corresponding one of the monitor jacks  34 . By inserting the plug in the jack  34 , a portion of the signal can be temporarily patched (e.g., by a patch cord) to additional test/monitoring equipment such as test equipment  45  shown in FIG. 7. Dual monitoring is particularly useful for performing different types of tests on a signal, or for test verification.  
         [0019]    In one particular application, the monitoring unit  30  is used in combination with DSX circuitry that lacks integral semi-permanent performance monitoring circuitry. By electrically coupling the cross-connect contacts of a DSX circuit desired to be monitored to the front connectors  38  of the unit  30 , semi-permanent monitoring can be provided (e.g., by equipment  43  shown in FIG. 7). Through monitor jacks  34 , dual monitoring can also be provided (e.g., by test equipment  45  shown in FIG. 7). The dual performance monitoring capability of the unit makes the unit useful for all types of DSX systems.  
       b. Detailed Description of Example Embodiment  
       [0020]    Referring to FIG. 2, the chassis  32  of the monitor unit  30  is shown. The chassis  32  includes top and bottom walls  70 ,  72  interconnected by left and right sidewalls  73 L,  73 R. Top and bottom walls  70 ,  72  and side walls  73 L,  73 R cooperate to define a chamber or housing for containing the jacks  34 . Mounting flanges  74  are mounted on the left and right side walls  73 L,  73 R. The mounting flanges  74  are used to connect the chassis  32  to a conventional telecommunications rack. Adjacent the front side  31  of the chassis  32 , the side walls  73 L,  73 R define access openings  75  for allowing cables to be routed through the side walls to the front connectors  38 . The openings  75  promote cable management by separating groups of cables.  
         [0021]    To conform to conventional international standards, the chassis  32  can have a length of about 19 inches. Alternatively, in accordance with standard United States specifications, the chassis could be configured to have a length of about 23 inches. Of course, other sizes of chassis could also be used.  
         [0022]    Referring to FIGS. 2 and 3, the front side  31  of the chassis  32  includes a central front plate  80  and two recessed front plates  82  positioned on opposite sides of the central plate  80 . The recessed plates  82  are set back relative to the central plate  80 . The monitor jacks  34  are mounted at the central plate  80 , and the groups  35 ,  37  of front connectors  38  are mounted at the recessed plates  82 .  
         [0023]    Referring to FIG. 2, the chassis  32  includes two dielectric panels  85  that are fastened to the central plate  80 . The panels  85  each define a plurality of vertical rows of openings  87  (e.g., 32 rows as shown in FIG. 3). The jacks  34  are secured to the back sides of the panels  85 . In one non-limiting embodiment, the monitor jacks  34  have a die-cast construction and include plug-receiving sleeves  89  (see FIG. 6) that align with corresponding tip springs  93   a ,  93   b  and ring springs  95   a ,  95   b  (see FIG. 6). To mount the jacks  34  to the panels  85 , the sleeves  89  of the jacks  34  are inserted within the openings  87  of the panels  85 . The jacks  34  are held securely in place by fasteners that engage the backsides of the panels  85 . The openings  87  in the panels  85  align the jacks in a plurality of vertical rows. A tracer lamp  91  is provided for each vertical row of jacks  34 . In a preferred embodiment, each vertical row of jacks  34  includes exclusively monitor jacks. In this embodiment, it will be appreciated that a monitor jack is a jack that does not include switching capabilities such as those present in a normal-through jack. Other embodiments are also contemplated in which other types of jacks (e.g., normal-through jacks) are included. Further, in other embodiments, the jacks could have a readily removable (e.g., snap fit) configuration such as those disclosed in U.S. Pat. No. 6,116,961, which is hereby incorporated by reference.  
         [0024]    The groups  35 ,  37  of front connectors  38  are mounted at the recessed front plates  82  of the chassis  32  and are accessible from the front side of the chassis  32 . As shown in FIGS. 2 and 3, each group  35 ,  37  is arranged in an array having vertical and horizontal rows of front connectors  38 . While the front connectors  38  have been shown as wire termination posts, it will be appreciated that a number of different types of connectors could be used. Representative types of connectors include insulation displacement connectors; co-axial connectors such as BNC connectors, 1.6/5.6 connectors or SMB connectors; or RJ series connectors such as RJ45 connectors, RJ48 connectors or RJ21 connectors. Further, while the front connectors  38  have been shown on opposite sides of the jacks, other configurations could be used. For example, the front connectors  38  could be located above or below the jacks  34 , or could be located only on one side of the jacks  34 .  
         [0025]    The groups  35 ,  37  of front connectors  38  are protected by front doors  100 . The front doors  100  include frames  102  pivotally connected to the chassis  32  at hinges  104 . The hinges  104  allow the doors  100  to be opened to provide enhanced access to the connectors  38 . In FIGS. 2 and 3, the left door is shown in an open position.  
         [0026]    The front doors  100  also include rear panels  106  fixedly connected to the frames  102 , and front panels  108  pivotally connected to the frames  102  at hinges  110 . The hinges  110  allow the front panels  108  to pivot outwardly to expose the front sides of the rear panels  106  (see the right door of FIG. 2). When closed, the front panels  108  snap or nest within the frames  102  (see the left door of FIG. 2). In use, designation information for the front connectors  38  can be recorded on labels placed on the front and back sides of the front panels  108 . Similarly, designation information for the rear connectors  40  can be recorded on labels placed on the rear panels  106 .  
         [0027]    Referring to FIGS. 4 and 5, the back side  33  of the chassis  32  includes a back plate  112 . The rear connectors  40  project rearwardly from the back plate  112 . While the connectors  40  have been shown as 75 ohm, co-axial BNC connectors, it will be appreciated that other types of connectors could also be used. Representative types of connectors include insulation displacement connectors; wire termination posts; other types of co-axial connectors such as 1.6/5.6 connectors or SMB connectors; or RJ series connectors such as RJ45 connectors, RJ48 connectors or RJ21 connectors.  
       c. Circuit Schematic for Example Embodiment  
       [0028]    [0028]FIG. 6 shows a circuit path schematic for the monitor unit  30  of FIGS.  2 - 5 . The circuit paths include front connectors  38   a ,  38   b  electrically connected (e.g., by wires or tracings in a circuit board) to rear connectors  40   a ,  40   b . Inductors  120   a ,  120   b  (i.e., baluns) are positioned between the front connectors  38   a ,  38   b  and the rear connectors  40   a ,  40   b  for converting signals from twisted pair (i.e., balanced signals) to co-axial signals (i.e., unbalanced). Resistors  122   a ,  122   b  are also provided between the front connectors  38   a ,  38   b  and the rear connectors  40   a ,  40   b . The resistors  122   a ,  122   b  provide signal resistance such that monitor level signals are output at the rear connectors  40   a ,  40   b.    
         [0029]    The circuit paths also include monitor jacks  34   a ,  34   b  having tip and ring springs  93   a ,  95   a  that are electrically coupled to the front connectors  38   a ,  38   b  (e.g., by wires or tracings on a circuit board). Resistors  124   a ,  124   b  are provided between the front connectors  38   a ,  38   b  and the monitor jacks  34   a ,  34   b . The resistors  124   a ,  124   b  provide signal resistance such that monitor level signals are output through the monitor jacks  34   a ,  34   b.    
         [0030]    In a preferred embodiment, the resistors  122   a ,  122   b ,  124   a  and  124   b  are adapted to provide an industry standard monitor level signal (e.g., approximately 20 dB for most applications). Of course, the decibel level of the monitor signal can vary depending upon the industry standard that is applicable. In one non-limiting embodiment, the resistors  122   a ,  122   b ,  124   a  and  124   b  each provide a resistance of about 523 ohms.  
         [0031]    Referring still to FIG. 6, each of the monitor jacks  34   a ,  34   b  includes a corresponding tracer lamp ground spring  126   a ,  126   b . The ground springs  126   a ,  126   b  normally do not engage corresponding contact springs  127   a ,  127   b . Contact springs  127   a ,  127   b  are mechanically coupled to monitor springs  95   a ,  95   b  by dielectric spacers  129   a ,  129   b . When a plug is inserted into either of the jacks  34   a ,  34   b , the springs  127   a ,  127   b  are flexed upwardly into contact with their corresponding tracer lamp ground springs  126   a ,  126   b  causing the corresponding tracer lamp  91  to be illuminated. Simultaneously, tracer lamps corresponding to DSX jacks electrically coupled to the monitor jacks  34   a ,  34   b  are also illuminated as described below. It will be appreciated that details regarding the operation of tracer lamp circuitry are well known in the art. A more detailed description of tracer lamp circuitry is provided in U.S. Pat. No. 6,116,961, which was previously incorporated by reference.  
         [0032]    [0032]FIG. 7 shows an example use for the monitoring unit  30 . In FIG. 7, the monitoring unit  30  is being used to provide signal monitoring of signals transferred between two cross-connected DSX jacks  501 ,  503 . The jacks  501 ,  503  are respectively coupled to pieces of telecommunications equipment  41   a ,  41   b  (e.g., digital switches, office repeaters, etc.). Wires  505  cross-connect the jacks  501 ,  503 . The wires  505  are terminated at cross-connect contacts  507 ,  509  (e.g., wire wrap pins) of the jacks  501 ,  503 . The monitoring unit  30  is electrically coupled to the DSX jacks  501 ,  503  by wires  511  terminated at the front connectors  38   a ,  38   b  and at the cross-connect contacts  507 . Portions of signals transferred between the equipment  41   a ,  41   b  through the jacks  501 ,  503  are carried to the monitoring unit  30  by wires  511 . The signals enter the monitoring unit  30  through the front connectors  38   a ,  38   b . From the front connectors  38   a ,  38   b , the signals are carried through resistors  122   a ,  122   b  to the inductors  120   a ,  120   b . At the inductors  120   a ,  120   b , the signals are converted from twisted pair to coaxial. The co-axial signals are output through the rear connectors  40   a ,  40   b . From the rear connectors  40   a ,  40   b , the signals are carried to the test/monitoring equipment  43 . To perform dual monitoring of the signals, tip-and-ring plugs can be inserted into the monitor jacks  34   a ,  34   b . By inserting the plugs in the jacks  34   a ,  34   b , portions of the signals can be temporarily patched (e.g., by a patch cord) to additional test/monitoring equipment  45 .  
         [0033]    When a plug is inserted into either of the jacks  34   a ,  34   b , the corresponding tracer lamp ground spring  126   a ,  126   b  is placed in electrical connection with the tracer lamp circuit of the monitor unit  30  as well as the tracer lamp circuits of the jacks  501 ,  503 . For example, when plugs are inserted within the jacks  34   a ,  34   b , the springs  127   a  and  127   b  are deflected upwardly into contact with ground springs  126   a  and  126   b , respectively. This causes the tracer lamp circuit of the monitoring unit  30  to be grounded and the tracer lamp  91  to be illuminated. Simultaneously, the tracer lamp circuits corresponding to both DSX jacks  501 ,  503  are also grounded causing their tracer lamps  513 ,  515  to also be illuminated. Tracer lamp wires  517  and  519  provide electrical connections between the tracer lamp circuits of the monitoring unit  30  and the two jacks  501 ,  503  such that all three circuits are simultaneously grounded when a plug is inserted into one of the monitor ports of the monitor unit  30 .  
         [0034]    The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.
A performance monitoring access device for a DSX system is disclosed herein. The monitoring device provides connection locations for readily connecting digital equipment to performance monitoring equipment. The monitoring devices allows for dual performance monitoring of digital equipment.