Patent Publication Number: US-9893470-B2

Title: Telecommunications cabling system, and electrical connection module shielding interface therefor

Description:
This application is a Continuation of U.S. application Ser. No. 14/368,073, filed 23 Jun. 2014, now U.S. Pat. No. 9,368,917 which is a National Stage Application of PCT/AU2012/001577, filed 20 Dec. 2012, which claims benefit of Serial No. 2011265514, Serial No. 2011265515, and Serial No. 2011265516, filed 23 Dec. 2011 in Australia and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a telecommunications cabling system for use in a telecommunications network. 
     BACKGROUND 
     In the field of telecommunications, wires used to carry the telecommunications signals are susceptible to noise from a variety of sources, including neighbouring wires in the same cable which may introduce near-end crosstalk (NEXT) or far-end crosstalk (FEXT), and nearby cables which may introduce alien crosstalk (AXT). As data transmission rates increase, the effect of this noise on error rates also increases. 
     Various attempts have been made in the past to minimise noise in telecommunications signals. For example, in twisted-pair cabling used in telecommunications networks, adjacent pairs in the cable generally have different twist rates, and the pairs may be individually shielded from electromagnetic interference using foil. The collection of pairs in the cable may be further shielded using a foil screen. This type of cable generally includes a grounding wire, also called a drain wire, to provide a grounding for the cable. 
     Typically, cables of the type described above are used to cross-connect telecommunications equipment at a premises. This may take place via patch panels which may include front and rear connection locations. 
     Another type of cabling system, known in the art as a “patch-by-exception” system, has hardwired cross-connections between connection modules to electrically connect ports of a data or voice switch/router with end user equipment. The connection modules generally include insulation displacement contacts (IDCs) onto which wires of respective twisted-pair cables are terminated to form the cross-connections, and the IDCs may include a spring contact which can be separated to break the connection. This type of connection module is sometimes known as a disconnect module. For example, the spring contacts may receive electrical contact-bearing fingers of a printed-circuit board (PCB) of a patch cord, for example of the type shown in PCT application PCT/EP2007/006369 (WO 2008/119370), the contents of which are hereby incorporated by reference in their entirety. The ends of such a patch cord may be plugged into the disconnect modules at any desired pair of locations in order to divert the data or voice signal from its original hardwired path to a new path between the desired pair of locations, thus creating a patched configuration which is an exception to the original (default) hardwired configuration. 
     It would be desirable to provide a patch-by-exception system with decreased susceptibility to electromagnetic interference, or at least to provide a useful alternative. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides a telecommunications cabling system, including:
         (a) an earthed support; and   (b) at least one connection module mounted to the earthed support, including:
           (i) a housing for a plurality of electrical contact members, the housing having a plurality of recesses to receive wires of at least one shielded cable;   (ii) at least one opening to receive an end of an electrical connector to place electrical contacts at the end of the electrical connector in direct or indirect electrical communication with at least some of the wires; and   (iii) a shielding interface for the connection module;   
           wherein the shielding interface is simultaneously contactable with shielding of the shielded cable, a corresponding shielding interface of the electrical connector, and the earthed support.       

     The shielding interface may be contactable with the earthed support by opposed ends of an electrically conductive member. 
     The at least one connection module may be mounted to the earthed support by a cable management member. The cable management member may include a bracket for the electrically conductive member. 
     In certain embodiments, the electrically conductive member is contactable with the shielding interface by an interference fit. 
     The shielding interface may include at least one conductive clasp to receive the shielding of the at least one shielded cable. The conductive clasp may have a substantially C-shaped cross section. The conductive clasp may have a recess to receive a cable tie to fasten the conductive clasp to the shielded cable. The or each said conductive clasp may extend from an elongate conductive strip or bar. 
     In certain embodiments, the shielding interface includes retaining means for retaining the shielding interface on the housing of the connection module. The retaining means may include one or more fingers configured to bear against the housing. The fingers may be received in grooves of the housing. The retaining means may include one or more apertures shaped to fit corresponding protrusions on the housing. Alternatively, or in addition, the retaining means may include one or more protrusions shaped to fit corresponding apertures in the housing. The one or more apertures and/or the one or more protrusions may be disposed oppositely to the one or more fingers on the shielding interface. 
     In certain embodiments, the housing includes an outer shell to which the shielding interface is attached. At least part of the outer shell may be conductive. In certain embodiments, the outer shell includes a conductive polymer. The conductive polymer may be a metallised polymer. 
     In embodiments with a conductive outer shell, the electrical contact members may be received in an insulating means of the housing to prevent electrical communication between the outer shell and the electrical contact members. The insulating means may include a plurality of insulating members. Each insulating member may include an upper pair of cavities and a lower pair of cavities to receive respective pairs of electrical contact members. The insulating members may have a central axis which is parallel to a long axis of the connection module, the cavities being angled at 45 degrees to the central axis. 
     In certain embodiments, the connection module includes two rows of pairs of insulation displacement contact slots. The electrical contact members may include bifurcated contact arms extending into respective insulation displacement contact slots for electrical connection to the wires of the shielded cable when seated in the insulation displacement contact slots. The or each opening of the housing may be arranged between opposed pairs of slots in said rows of slots, each being shaped to receive the end of an electrical connector. A resilient end of each electrical contact member of an upper row (of the two rows of pairs of insulation displacement contact slots) may in contact with a resilient end of a corresponding electrical contact member of a lower row. 
     In certain embodiments, wire-receiving recesses of the insulating means are accessible via the recesses of the connection module housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings in which: 
         FIG. 1  is a perspective view of an example of a telecommunications cabling system including connection modules mounted to a back-mount frame; 
         FIG. 2  is a partial exploded view of the system of  FIG. 1 ; 
         FIG. 3  is a detail of part of the system of  FIG. 1 ; 
         FIG. 4  is a top plan view of a connection module having a plurality of shielded cables terminated thereon; 
         FIG. 5  is a perspective view of the module of  FIG. 4 ; 
         FIG. 6  is a perspective view of the module of  FIGS. 4 and 5 , prior to termination of the cables; 
         FIG. 7A  is an exploded view of the module of  FIG. 6 ; 
         FIG. 7B  is a detail of part of  FIG. 7A ; 
         FIG. 8A  is a bottom plan view of the module of  FIG. 6 ; 
         FIG. 8B  is a rear plan view of the module of  FIG. 6 ; 
         FIG. 9A  is a rear plan view of an example of a contact carrier for use with the module of  FIG. 6 ; 
         FIG. 9B  is a front plan view of the contact carrier of  FIG. 9A ; 
         FIG. 9C  is a top plan view of the contact carrier; 
         FIGS. 9D and 9E  are front and rear perspective views, respectively, of the contact carrier; 
         FIG. 10A  is a top perspective view of an example of a shielding bar for use with the connection module of  FIG. 6 ; 
         FIG. 10B  is a top plan view of the shielding bar of  FIG. 10A ; 
         FIG. 10C  is a front plan view of the shielding bar; 
         FIG. 10D  is a right-side view of the shielding bar; 
         FIG. 11A  is a top perspective view of an example rear-facing patch plug; 
         FIG. 11B  is an exploded view of the patch plug of  FIG. 11A ; 
         FIG. 11C  is a cross-section through the line A-A of  FIG. 11A ; and 
         FIG. 12  shows a side view of  FIGS. 4 and 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Where the terms “front”, “rear”, “top”, “bottom”, “upper”, “lower” and the like are used below, it will be understood that these are used simply to describe the orientations of various components relative to each other, and are not intended to be construed in an absolute sense. Accordingly, the skilled person will understand that these terms should be interchanged appropriately when the orientation of the system (relative to a user, for example) is changed. 
     Referring to  FIGS. 1 to 3 , there is shown a telecommunications cabling system  10  including an earthed support (backmount frame)  12  to which connection modules  100  are mounted, via respective cable managers  150 . In use, telecommunications cables  50   a  housed in backmount frame  12  can be fed through cable retention members  156  on respective top surfaces of the cable managers  150 , and wires of the cables  50   a  terminated on the connection modules  100  ( FIG. 4 ). 
     With reference to  FIG. 7A , each connection module  100  includes a housing for a plurality of electrical contact members  212 . Each electrical contact member includes an insulation displacement contact (IDC) which is seated inside the housing in a manner which will later be described. The housing includes an outer shell  200  and an inner shell  220  between which electrical contact members  212  are retained. 
     The housing  200 ,  220  has a plurality of recesses  202  ( FIG. 8 ) to receive wires of at least one shielded cable  50   a  for termination of the wires onto the electrical contact members  212 . The housing also includes an opening to receive an end of an electrical connector, for example a front-facing patch plug  300  or a rear-facing patch plug  400 , to place electrical contacts at the end of the patch plug  300  or  400  in electrical communication with at least some of the wires. 
     Returning to  FIGS. 2 and 3 , the system  10  includes a shielding interface  110   a  for each disconnect module  100 . The shielding interface  110   a  is simultaneously contactable with shielding  52   a  of the shielded cable  50   a  ( FIGS. 1, 4 and 5 ), a corresponding shielding interface  500  of the patch plug  400  ( FIGS. 11B, 11C, 12 ), and the earthed support  12 . 
     Advantageously, simultaneous contact between the shielding interface  110   a , shielding of the cable  50   a , the corresponding shielding interface  500  of patch cord  400  and earthed support (backmount frame)  12  provides a common earth throughout the electrical connections of the system  10 , thereby improving the signal-to-noise ratio of the system  10 . 
     With continued reference to  FIGS. 1 to 3 , each cable manager  150  includes a pair of projections  152  (only one of which is shown in the Figures), one at the rear of each of its end panels  151 , which are shaped to sit within apertures  14  in the frame  12 . End panels  151  of the cable manager  150  are preferably resilient panels which can flex to allow the projections  152  to locate within the apertures  14  and hold the cable manager  150  in place on the backmount frame  12 . 
     At the front of each end panel  151 , a hook  154  of a snap-fit mechanism projects forwardly of cable manager  150 . The hooks  154  fit within corresponding recesses  104  ( FIG. 8B ) of the disconnect module  100  to retain the module  100  on the cable manager  150 . 
     The disconnect module  100  can accommodate up to 24 pairs of wires in each row, although it will of course be appreciated that any desired number of pairs can be accommodated in a single module. Thus, for example, the wires of six twisted-pair cables, each including four pairs  50   a . 1  to  50   a . 4  as shown in  FIGS. 4 and 5 , can be terminated on the top row of a module  100 . Accordingly, the cable manager  150  includes six cable retention members  156 , one for each cable. Each cable retention member  156  has a resilient downwardly-arched arm  156   a  located opposite a pair of protrusions  156   b  on the upper surface of the cable manager  150  ( FIG. 2 ). The gap between the arm  156   a  and the protrusions  156   b  is less than the thickness of a cable  50   a , such that the cable  50   a  can be pushed into the gap, thereby deflecting the arm  156   a  upwards and allowing the cable to pass over the protrusions  156   b  such that the cable is retained between arm  156   a  and protrusions  156   b.    
     In the system  10 , a first set of cables  50   a , which may each for example have one end connected to a port of a switch or router, may be passed through an aperture  16  in backmount frame  12 . The wire pairs  50   a . 1  to  50   a . 4  of the first set of cables  50   a  are terminated onto the IDCs of upper rows  107  of a first set of disconnect modules  100 . A second set of cables  50   b  ( FIG. 12 ), which may have their respective ends connected to end user equipment such as computer systems (provided with network interfaces), telephony equipment and the like, may also be passed through the aperture  16 , and the wires of the second set of cables terminated onto the IDCs of upper rows  107  of a second set of disconnect modules  100 . Cross-connects may then be formed by terminating a series of cables between respective lower rows  108  of the first and second sets of disconnect modules  100 . 
     Cable manager  150  may include a plurality of forwardly projecting arms  158 . The arms  158  provide mechanical support for disconnect module  100  along its length, particularly when wires are terminated into IDC slots of the disconnect module  100  as will later be described. 
     Cable manager  150  includes a bracket to receive an electrically conductive member  160 . The electrically conductive member  160  has at one end a finger  164  and at its opposite end two pairs of tines  162 . As best seen in  FIG. 3 , when the cable manager  150  is mounted to the backmount frame  12  and the disconnect module  100 , the finger  164  of shielding member  160  contacts with the backmount frame  12 , and the tines  162  engage with a shielding bar  110  of the disconnect module  100  to form an interference fit. This ensures, when the backmount frame  12  is connected to a protective earth, that the shielding bar  110  is also earthed. 
     Referring now to  FIGS. 6, 7A, 7B, 8A and 8B , there is shown a connection module  100  including an outer shell  200  and an inner shell  220 . Housed between the inner shell  200  and the outer shell  220  are a plurality of electrical contact members  212  which are arranged as an upper row  212   a  and a lower row  212   b . Blades  257   a  of the electrical contact members  212   a  of the upper row are at least partially exposed via recesses  202  ( FIG. 8A ) between adjacent islands  107   a  of an upper row  107  of the module  100 . Similarly, blades  257   b  of the electrical contact members  212   b  of the lower row are at least partially exposed via recesses  202  between adjacent islands  108   a  of a lower row  108  of the module  100 . 
     The outer shell  200  preferably includes an electrically conductive material. For example, the outer shell may be formed of a metal or a metallised polymer, and/or may include a conductive surface coating, for example a metallic coating. The entire outer shell may be electrically conductive, or may be formed of individual electrically conductive portions, which may or may not be separated by non-conductive portions. The electrical conductivity of the outer shell  200  provides shielding against alien crosstalk. 
     Each electrical contact member  212   a ,  212   b  may be received in an insulating means  214  comprising a plurality of insulating members (contact carriers)  900 . As shown in  FIGS. 9A to 9E , each contact carrier  900  includes an upper pair  910  and a lower pair  912  of cavities. Accordingly, the blades  257   a  of upper contact members  212   a  are received in upper cavities  910 , and the blades  257   b  of lower contact members  212   b  are received in lower cavities  912 . 
     The insulating means  214  depicted in the drawings comprises a plurality of individual contact carriers  900 . However, it will also be appreciated that the insulating means can be formed as a unitary component, for example by an injection moulding process. 
     To assemble the module  100 , front ends (blades)  257   a ,  258   b  of electrical contact members  212   a ,  212   b  are inserted into contact carriers  900 . Resilient rear ends  258   a ,  258   b  of the upper  212   a  and lower  212   b  contact members are inserted into recesses  224  of the inner shell  220  such that the rear ends  258   a ,  258   b  are in electrical contact, and outer shell  200  is then placed over the inner shell  220  and contact carriers  900  such that the contact carriers  900  are seated in cavities (not shown) in the outer shell  200 , with a central rib  902  of each contact carrier  900  ( FIG. 9C ) protruding into recesses  202  in the outer shell  200  ( FIG. 8A ). When the module  100  is assembled, wire-receiving recesses  904  of the contact carriers  900  are accessible via the recesses  202  of the outer shell  200 . 
     To assist in retaining the inner shell  220  on the outer shell  200 , resilient tongues  222  are provided on the inner shell  220 . These may engage directly with outer surfaces of the outer shell  200 , or may be disposed so as to engage with protrusions  206  on the outer shell surface. The outer shell  200  may include protrusions  206  on both its upper and lower surfaces (only those protrusions on the upper surface being shown in  FIG. 7A ). 
     The outer shell  200  of module  100  has a plurality of grooves  204  formed on its lower surface to receive fingers of a shielding bar as will later be described. The grooves  204  extend from the rear of outer shell  200 , across the width of the lower surface to the front of the outer shell, and around the front, ending in a flattened portion  205  ( FIG. 6 ) in the lower row  108  of the module  100 . 
     In like fashion, a further plurality of grooves may also be formed on the upper surface of outer shell  200 , in opposed relationship to the grooves  204 , if desired. If so, said grooves may end in flattened portions in the upper row  107  of the module  100 . 
     Turning now to  FIGS. 10A to 10D , there is shown a shielding bar  110   a  for use with the module  100  and system  10 . The shielding bar includes an elongate body in the form of a bar or strip  111  of an electrically conductive material. The elongate strip  111  has projecting from one of its long edges a series of clasps  120   a , each of which is associated with a finger  114  having a hooked end  115 . Fingers  114  are rigid, but may also be made resilient if desired. The elongate strip  111  also has formed therein a series of holes  112  which are shaped and located to fit the protrusions  206  on the surface of the outer shell  200  of the connection module  100 . 
     Each of the clasps  120   a  is substantially C-shaped in cross section and has a conduit  126  which is sized and shaped so as to accommodate a shielded cable  50   a  as shown in  FIGS. 4 and 5 . Each clasp  120   a  includes a pair of ears  122  defining a recess  124  therebetween. The recess  124  is sized to fit a cable tie which is wrapped around the clasp  120   a  in order to secure the clasp  120   a  to the shielding foil  52   a  of the shielded cable  50   a  ( FIGS. 4 and 5 , cable tie not shown) in order to maintain electrical connection between the shielding bar  110   a  and the foil  52   a.    
     To fit the shielding bar  110   a  to the module  100  shown in  FIGS. 7A, 7B and 8A , inner shell  220  is removed (if it has previously been attached to outer shell  200 ). The fingers  114  are seated within grooves  204  on the lower surface of the outer shell  200 , such that hooked ends  115  pass into the space defined between upper row  107  and lower row  108  of the module  100 , and are received in seating regions  205  ( FIG. 6 ). Apertures  112  of the shielding bar are fitted over protrusions  206  on the lower surface of outer shell  200  to further assist in retaining the shielding bar  110   a  on the outer shell  200 . 
     The shielding bar  110   a  shown in  FIGS. 10A to 10D  includes fingers  114  and hooked ends  115  for the purpose of establishing electrical contact with a corresponding shielding member of a patch plug, as will later be described. However, it will be understood that, if the shielding bar is to be used primarily to contact the foil (via clasps  120 ) of a shielded cable  50   a , the fingers  114  may be omitted. A fingerless shielding bar of this type may be affixed to the outer shell  200  of a module  100  by fitting apertures  112  over protrusions  206  on the outer shell surface as previously described. 
     So, for example, if a first shielding bar has been attached by fitting its fingers  114  to grooves  204  in the lower surface of the outer shell  200 , a second, fingerless shielding bar may then be attached to the upper surface of the outer shell  200 . If both the upper and lower surfaces of the outer shell  200  include grooves  204 , then it will be appreciated that a second, fingered, shielding bar  110   b  ( FIG. 12 ) may be attached in similar fashion to the first shielding bar  110   a  as described above. 
     Once the shielding bar or bars  110   a ,  110   b  have been attached to outer shell  200 , inner shell  220  is then re-attached (or attached), the tongues  222  being pushed over the shielding bar (or bars)  110   a ,  110   b  so as to secure the inner shell  220  to both the shielding bar (or bars)  110   a ,  110   b  and the outer shell  200 . 
     With reference now to  FIGS. 11A to 11C , there is shown an electrical connector, in the form of a rear-facing patch plug  400 , for use with the system  10 . 
     The electrical connector  400  includes a connector body having a first member  402  and a second member which is made up of an upper shell  406  and a lower shell  404 . Connector  400  further includes an electrical connector element  408 , an insulation shield  410  and a biasing means  412 , such as a spring. The first member  402  has an opening  414  formed through the member  402  for receiving one or more wires  417   a  from an electric cable  416  (only the very end of which is shown). The connector  400  can be used with any type of electric cable  416 , but in the present example, the cable  416  is a shielded multi-cored cable with wires  417   a  corresponding to one or more twisted pairs  417 . Each twisted pair  417  is surrounded by a metallic foil, and the collection of pairs is surrounded by a shielding foil (in similar fashion to shielding foil  52   a  of cable  50   a , as shown in  FIGS. 1, 4 and 5 ). 
     The first member  402  has latching means formed on an inner surface of the member  402 . The latching means includes one or more resilient latching posts  418   a  and  418   b , each having an enlarged head portion which includes a shoulder that gradually increases the cross-sectional thickness of the head portion in a direction away from the exposed end of the latching post  418   a  and  418   b . The head portion includes a flanged portion formed substantially normal to the length of the latching post  418   a  and  418   b , which defines the transition from the larger cross-sectional thickness of the head portion to a smaller cross-sectional thickness of the latching post  418   a  and  41   b . The latching posts  418   a  and  418   b  on the first member  402  are aligned with a corresponding recess  420  formed in the upper shell  406  of the second member. When the first member  402  and second member  404 ,  406  are coupled together, the head portion of a latching post  418   a  and  418   b  engages within a respective recess  420  in the upper shell  406  so that the resilience of the latching posts  418   a  and  418   b  securely holds the first member  402  and upper shell  406  together. 
     The first member  402  and the upper shell  406  of the second member, when coupled together, define a cavity between the parts  402  and  406 . The upper shell  406  of the second member includes one or more wiring slots  422 , each for receiving the end of a respective wire  417   a  from the cable  416 . The wiring slots  422  are preferably IDC slots with contacts  424  which displace the insulation at the end of a wire within the cavity to establish electrical contact. For example, each contact slot  424  includes a surface made of a conducting material (e.g. copper) for directly contacting and making an electrical connection with the end of a wire (not shown) held in place by a wiring slot  422  of upper shell  406 . The size of each contact slot  424  is sufficiently small to securely grip the end of a wire. 
     The connector element  408  includes one or more fingers  426 , each finger  426  having a contact portion  428  for making electrical contact. The connector element  408  is substantially flat and has conducting paths (not shown) formed on the upper surface  430  and/or the lower surface  432  to provide an electrical connection between each contact slot  424  with a respective contact portion  428  of a finger  426 . The connector element  408  may be a printed circuit board with etched conducting paths on one or both sides  430 ,  432 . In the arrangement shown in  FIG. 11B , the contact slots  424  for receiving wires of a twisted pair are connected by conducting paths to respective contact portions  428  on adjacent fingers  426 . 
     The connector element  408  is made for mating assembly with the upper shell  406 . The connector element  408  includes one or more retaining notches  434   a  and  434   b  that engages with a corresponding retaining recess  436  formed in the upper shell  406  to securely couple the parts  406  and  408  together. 
     The adjustable insulation shield  410  is made of a non-conductive material (e.g. polycarbonate or polyvinylchloride), and has one or more guiding slots  446   a  and  446   b  formed in the shield  410 . In some embodiments, as shown in  FIG. 11B , the guiding slots  446   a  and  446   b  are formed through sidewalls of the shield  410 . In other embodiments, the guiding slots  446   a  and  446   b  may comprise recesses formed on the inner surface of the shield  410  but not formed through the sidewalls of the shield  410 . 
     The guiding slots  446   a  and  446   b  engage with a corresponding guiding protrusion  448   a  and  448   b  formed on the outer surface of the lower shell  404 , so that the shield  410  is able to move by sliding relative to the second member  404 ,  406 , and wherein the movement of the shield  410  is guided by the guiding protrusions  448   a  and  448   b . The guiding protrusions  448   a  and  448   b  are sufficiently long and snugly received in slots  446   a  and  446   b  so as to maintain stability of the shield  410  during movement. 
     The shield  410  is moveable along the length of the second member  404 ,  406  between an extended second position and a retracted first position, such that when the shield  410  returns to the first position, the contact portions  428  of the fingers  426  are exposed for direct contact. When the shield  410  is moved to the second position, the shield covers the contact portions  428  of the fingers  426  to minimise direct contact with the contact portions  428 . 
     The electrical connector  400  includes biasing means  412  that tends to move the shield  410  towards the second position. The biasing means  412  may include a suitable form of compression spring, and may specifically comprise an S-shaped spring as shown in  FIG. 11B . The biasing means  412  is positioned between the shield  410  and the lower shell  404  of the second member, and the biasing means  412 , when compressed, pushes against a boss portion  445  of the lower shell  404  and an inner wall of the shield  410  to bias the shield  410  towards the second position. The S-shaped spring shown in  FIG. 11B  has one end registered with boss portion  445  and has its other end registered with another boss portion (not shown) on shield  410  so that the spring is retained in position during compression and expansion. 
     A u-shaped supporting portion  444  on lower shell  404  is positioned to mate with a complimentary u-shaped slot extending centrally in the direction of contact portions  428  on connector element  408 . When connector  400  is assembled, supporting portion  444  assists in holding connector element  408  in place within the connector body. A keying finger  442  extends from lower shell  404  and aids in ensuring electrical connector  400  is correctly terminated when connecting to a patch panel, for example at connection module  100 . 
     The electrical connector  400  includes, in the first member  402 , a substantially T-shaped slot  460  to receive an upright portion  502  of contact shielding member  500 . The shielding member  500  includes a recessed portion  510 , disposed substantially perpendicular to the upright portion  502 , around which the drain wire and shielding foil of cable  416  are wrapped. 
     As shown in  FIG. 11C , contact shielding member  500  includes an exposed portion  504  which protrudes through an opening in lower shell  404  so as to lie outside the body of the connector  400 . Exposed portion  504  underlies the u-shaped supporting portion  444  of the lower shell  404 . 
     Forward-facing patch plug  300  is configured substantially identically to rear-facing patch plug  400 , except that a cable-receiving aperture of forward-facing plug  300  is located at an end of a first member of the plug  300  which is disposed opposite the contacts of the plug  300 , in contrast to rear-facing plug  400  in which the cable-receiving aperture  414  is disposed adjacent the contacts  428  of the plug  400 . 
     Turning now to  FIG. 12 , the connector  400  is shown terminated at a connection module  100  to which are attached two shielding bars  110   a ,  110   b . Upper shielding bar  110   a  is in electrical contact, via clasp  120   a , with a shielding foil  52   a  of a first shielded cable  50   a  which includes four shielded pairs of wires (only three pairs  50 . 1   a ,  50 . 2   a ,  50 . 3   a  of which are shown) which are terminated onto IDCs of the module  100  as described above. Similarly, lower shielding bar  110   b  is in electrical contact via its clasp  120   b  with a shielding foil  52   b  of a second shielded cable  50   b , which includes four shielded pairs of wires (only three pairs  50 . 1   b ,  50 . 2   b ,  50 . 3   b  of which are shown) which are terminated onto IDCs of the module  100 . 
     Finger  114   b  of shielding bar  110   b  extends around the lower part  108  of module  100  and terminates in hooked portion  115   b  which is seated in a seat  205  of groove  204  ( FIG. 6 ). With the connector  400  inserted, exposed portion  504  aligns and comes into contact with hooked portion  115   b , such that the shielding bar  110   b  is in electrical contact with the contact shielding member  500 , and in turn with the drain wire and shielding foil of the cable  416  of connector  400 . 
     As can be seen from the foregoing discussion, each element of the system  10  includes means for electrically contacting (directly or indirectly) the grounded support means  12  such that a common earth is established throughout the system  10 . In the absence of patch plugs  300 ,  400 , the shielding foils of cables  50   a  (with wires terminated on upper row  107  of module  100 ) and  50   b  (with wires terminated on lower row  108 ) are in contact with respective shielding bars  110   a ,  110   b , which in turn are in contact with the electrically conductive member  160 , which is in turn in contact with the backmount frame  12 . When a patch plug  400  is inserted, contact shielding member  500  (which is in contact with the drain wire and shielding foil of cable  416 ) comes into contact with shielding bar  110   b  (via hooked portion  115   b  as shown in  FIG. 12 ) so that the common earth is maintained. 
     Throughout this specification, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. 
     The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 
     LISTING OF PARTS 
     
         
           10  cabling system 
           12  backmount frame 
           14  apertures of backmount frame (to fit cable manager) 
           16  aperture (to receive cables) 
           50   a  upper shielded cable 
           50 . 1   a - 50 . 4   a  pairs of upper shielded cable 
           50   b  lower shielded cable 
           50 . 1   b - 50 . 4   b  pairs of lower shielded cable 
           52   a  shielding foil of upper cable 
           52   b  shielding foil of lower cable 
           60  label holder 
           100  connection module 
           104  recesses to fit hooks of cable manager 
           107  upper row of connection module 
           107   a  islands of upper row 
           108  lower row of connection module 
           108   a  islands of lower row 
           110   a  upper shielding bar 
           110   b  lower shielding bar 
           111  elongate body of shielding bar 
           112  holes of shielding bar 
           114  fingers of shielding bar 
           115  hooked portions of shielding bar 
           120   a  clasps of upper shielding bar 
           120   b  clasps of lower shielding bar 
           122  ears of clasps 
           124  recess for cable tie 
           126  conduit for shielded cable 
           150  rear cable manager 
           151  end panels of cable manager 
           152  protrusions of cable manager 
           154  hook of snap-fit for cable manager 
           156  cable retention member 
           156   a  arm of cable retention member 
           156   b  protrusions on upper surface of cable manager 
           158  forwardly projecting arms 
           160  electrically conductive member 
           162  tines of electrically conductive member 
           164  finger of electrically conductive member 
           200  inner shell of connection module 
           202  recesses of outer shell 
           204  grooves for fingers of shielding bar 
           205  seat for hooked portion of shielding bar 
           206  protrusions on outer shell surface 
           212  electrical contact members 
           212   a  upper row of electrical contact members 
           212   b  lower row of electrical contact members 
           214  insulating members (contact carriers) 
           220  inner shell 
           222  tongues of inner shell 
           224  contact-receiving recesses of inner shell 
           300  forward-facing patch plug 
           400  rear-facing patch plug 
           402  first member of patch plug 
           404  lower shell of second member 
           406  upper shell of second member 
           408  electrical connector element (PCB) 
           410  insulation shield 
           412  spring 
           414  cable aperture 
           416  cable 
           417  twisted pair of cable 
           417   a  wires of cable 
           418   a ,  418   b  latching posts 
           420  recesses for latching posts 
           422  wiring slots 
           424  contact slots 
           426  contact fingers 
           428  contacts 
           430  first side of PCB 
           432  second side of PCB 
           434   a ,  434   b  retaining notches 
           436  retaining recess 
           442  keying finger 
           444  supporting portion 
           445  boss 
           446   a ,  446   b  guiding slots 
           448   a ,  448   b  guiding protrusions 
           460  T-shaped slot 
           500  contact shielding member 
           502  upright portion of contact shielding member 
           504  exposed portion of contact shielding member 
           510  recessed portion of contact shielding member