Abstract:
An apparatus and method for crosstalk compensation in a jack of a modular communications connector includes connected to the plug interface contacts proximate the plug/jack interface. The structure configured to allow the current to flow generally orthogonal to the plug interface contact.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 15/220,789, filed Jul. 27, 2016, which is a continuation of U.S. patent application Ser. No. 14/474,479, filed Sep. 2, 2014, which issued as U.S. Pat. No. 9,407,044 on Aug. 2, 2016; which is a continuation of U.S. patent application Ser. No. 12/916,687, which was filed on Nov. 1, 2010, which issued as U.S. Pat. No. 8,826,532 on Sep. 9, 2014; which is a continuation of U.S. patent application Ser. No. 11/833,686, filed Aug. 3, 2007, which issued as U.S. Pat. No. 7,823,281 on Nov. 2, 2010; which is a continuation of U.S. patent application Ser. No. 11/078,816, filed Mar. 11, 2005, which issued as U.S. Pat. No. 7,252,554 on Aug. 7, 2007; which claims the benefit of U.S. Provisional Application Ser. No. 60/558,657, filed Apr. 1, 2004; and U.S. Provisional Application Ser. No. 60/552,995, filed Mar. 12, 2004, which are incorporated herein by reference in their entireties. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to electrical connectors and more particularly relates to modular communication connectors that utilize compensation techniques to reduce net crosstalk generated by the combination of a plug and a jack of a connector assembly. 
       BACKGROUND 
       [0003]    Computer networks, including local area networks (LANs) and wide area networks (WANs), are becoming increasingly prevalent as the number of computers and network devices in the workplace grows. These computer networks utilize data communication cables and electrical connectors to transmit information between various components attached to the network. The electrical connectors are typically configured to include a plug that is connectable to a jack mounted in the wall, or integrated into a panel or other telecommunication equipment. The jack typically includes a housing that holds an array of closely spaced parallel contacts for contacting corresponding conductors of the plug. The contacts of a jack are often mounted onto a printed circuit board. An RJ45 plug and jack connector assembly is one well-known standard connector assembly having closely spaced contacts. 
         [0004]    Over the past several years, advances in computer networking technology have facilitated a corresponding increase in the rate at which data can be transmitted through a network. Conventional connectors have been used to transmit low-frequency data signals without any significant crosstalk problems. However, when such connectors are used to transmit high-frequency data signals, crosstalk generated within the connector increases dramatically. This crosstalk is primarily due to the capacitive and inductive couplings between the closely spaced parallel conductors within the jack and/or the plug. 
         [0005]    A wide variety of improvements have been made in the design of electrical connectors to reduce crosstalk occurring within connectors. One example is disclosed in U.S. Pat. No. 6,305,950, which is commonly assigned to Panduit Corporation. This type of connector uses a particular conductor configuration in conjunction with a multi-layered printed circuit board containing capacitors to achieve a reduction in the crosstalk effect. However, due to the high level of crosstalk occurring in the plug for this connector at very high-frequency signal rates, the tuning effect achievable by the capacitors can still be difficult to accomplish. As such, further improvements in the design of connectors are still needed to address such problems and provide improved crosstalk performance. 
       SUMMARY OF THE INVENTION 
       [0006]    According to one embodiment of the present invention, a communications connector utilizes a flexible printed circuit to provide crosstalk compensation. The flexible printed circuit is in electrical contact with contacts of the communications connector. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0007]      FIG. 1  is an exploded view of an electrical jack according to one embodiment of the present invention; 
           [0008]      FIG. 2  is an exploded view of a contact assembly showing the use of a flexible printed circuit; 
           [0009]      FIG. 3  is a rear perspective view of the contact assembly of  FIG. 2 ; 
           [0010]      FIG. 4  is a side cutaway view of the electrical jack of  FIG. 1 ; 
           [0011]      FIG. 5  is a side cutaway view of an electrical jack according to an alternative embodiment of the present invention; 
           [0012]      FIG. 6  is a plan view of a flexible printed circuit showing zones A-F; 
           [0013]      FIG. 6A  is a detail view of Zone A of the flexible printed circuit of  FIG. 6 ; 
           [0014]      FIG. 6B  is a detail view of Zone B of the flexible printed circuit of  FIG. 6 ; 
           [0015]      FIG. 6C  is a detail view of Zone C of the flexible printed circuit of  FIG. 6 ; 
           [0016]      FIG. 6D  is a detail view of Zone D of the flexible printed circuit of  FIG. 6 ; 
           [0017]      FIG. 6E  is a detail view of Zone E of the flexible printed circuit of  FIG. 6 ; 
           [0018]      FIG. 6F  is a detail view of Zone F of the flexible printed circuit of  FIG. 6 ; 
           [0019]      FIG. 6G  is a plan view of the flexible printed circuit of  FIG. 6 , with sectional lines; 
           [0020]      FIG. 6H  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with a first conductor; 
           [0021]      FIG. 6I  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with a second conductor; 
           [0022]      FIG. 6J  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with a third conductor; 
           [0023]      FIG. 6K  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with a fourth conductor; 
           [0024]      FIG. 6L  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with a fifth conductor; 
           [0025]      FIG. 6M  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with a sixth conductor; 
           [0026]      FIG. 6N  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with a seventh conductor; 
           [0027]      FIG. 6O  is a plan view of the flexible printed circuit of  FIG. 6  showing a conductive trace associated with an eighth conductor; 
           [0028]      FIG. 7  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line A-A of  FIG. 6   g;    
           [0029]      FIG. 8A  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line B-B of  FIG. 6G ; 
           [0030]      FIG. 8B  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line C-C of  FIG. 6G ; 
           [0031]      FIG. 9  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line D-D of  FIG. 6G ; 
           [0032]      FIG. 10A  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line E-E of  FIG. 6G ; 
           [0033]      FIG. 10B  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line F-F of  FIG. 6G ; 
           [0034]      FIG. 11  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line G-G of  FIG. 6G ; 
           [0035]      FIG. 12  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line H-H of  FIG. 6G ; 
           [0036]      FIG. 13  is a sectional view of the flexible printed circuit of  FIG. 6  taken along the line I-I of  FIG. 6G ; 
           [0037]      FIG. 14  is a detail view of the detail J of  FIG. 6G ; 
           [0038]      FIG. 15  is a detail view of the detail K of  FIG. 6G ; 
           [0039]      FIG. 16  is a detail view of the detail L of  FIG. 6G ; 
           [0040]      FIG. 17  is a detail view of the detail M of  FIG. 6G ; 
           [0041]      FIG. 18  is a side cutaway view of an electrical jack according to another alternative embodiment of the present invention; 
           [0042]      FIG. 19  is an exploded view of the electrical jack of  FIG. 18 ; 
           [0043]      FIG. 20  is a detail view of the detail N of  FIG. 19 ; 
           [0044]      FIG. 21  is a perspective view of a contact-and-housing assembly of the electrical jack of  FIG. 18 ; 
           [0045]      FIG. 21A  is a perspective view of an alternate embodiment of a contact-and-housing assembly of the electrical jack of  FIG. 18 ; 
           [0046]      FIG. 22  is a perspective view of the contact-and-housing assembly of the electrical jack of  FIG. 18 ; 
           [0047]      FIG. 23  is a perspective view of IDCs and associated stems according to one embodiment of the present invention; 
           [0048]      FIG. 24  is a top view of IDCs of  FIG. 23 ; 
           [0049]      FIG. 25  is a front view of the IDCs of  FIG. 23 ; 
           [0050]      FIG. 26  is a rear view of the IDCs of  FIG. 23 ; 
           [0051]      FIG. 27  is a side view of the IDCs of  FIG. 23 ; 
           [0052]      FIG. 28  is a detail view of the detail O of  FIG. 27 ; 
           [0053]      FIG. 29  is a detail view of the detail P of  FIG. 27 ; 
           [0054]      FIG. 30  is a sectional view taken along the line Q-Q of  FIG. 27 ; 
           [0055]      FIG. 31  is a plan view of an alternative FPC  200 , which may be used with the jack shown in  FIGS. 33-45 ; 
           [0056]      FIG. 32  is a perspective view of the variable capacitance  250  shown in  FIG. 31 ; 
           [0057]      FIG. 33  is a side cutaway view of the front portion of a jack, showing contact  1  or  8  in a combed position; 
           [0058]      FIG. 34  is a side cutaway view of the front portion of a jack, showing contact  1  or  8  in a solid-plug position; 
           [0059]      FIG. 35  is a side cutaway view of the front portion of a jack, showing contacts  2 ,  4 ,  5 , or  7  in a combed position; 
           [0060]      FIG. 36  is an upper right-hand front exploded perspective view of a jack in accordance with an embodiment of the present invention; 
           [0061]      FIG. 37  is a close-up view showing detail of the front sled with contacts, including spring contacts; 
           [0062]      FIG. 38  is a close-up view showing detail of the rear contact guides; 
           [0063]      FIG. 39  is a lower left-hand rear exploded perspective view of a jack in accordance with an embodiment of the present invention; 
           [0064]      FIG. 40  is a close-up view showing detail of the bottom of the front sled with contacts, including spring contacts; 
           [0065]      FIG. 41  is a first rear perspective view of the housing of a jack in accordance with an embodiment of the present invention; 
           [0066]      FIG. 42  is a second rear perspective view of the housing of a jack in accordance with an embodiment of the present invention; 
           [0067]      FIG. 43  is a perspective view of the contacts, including spring contacts; 
           [0068]      FIG. 44  is a perspective view of a long contact; and 
           [0069]      FIG. 45  is a perspective view of a short contact. 
           [0070]      FIG. 46  is an isometric view of a communication system showing a patch panel capable of using high speed RJ45 jacks of the present invention. 
           [0071]      FIG. 47  is an isometric view of second embodiment of a high speed RJ45 jack of the present invention mated with a plug. 
           [0072]      FIG. 48  is an exploded isometric view of the RJ45 jack of  FIG. 47 . 
           [0073]      FIG. 49  is a rotated isometric view of a front sled assembly to be used in the high speed connector of  FIG. 47 . 
           [0074]      FIG. 50  is an exploded isometric view of the front sled assembly of  FIG. 49 . 
           [0075]      FIG. 51  is a cross-sectional view of the mated plug and jack of  FIG. 47  taken along line  51 - 51 . 
           [0076]      FIG. 52  is an isometric view of the front sled assembly of  FIG. 49  (with the sled being shown as a dashed outline) highlighting the signal paths of the 3-6 split pair. 
           [0077]      FIG. 53  is an isometric view from the bottom of the front sled assembly of  FIG. 52 . 
           [0078]      FIG. 54  is a side view of the front sled assembly of  FIG. 52 . 
           [0079]      FIG. 55  is an isometric view of a contact assembly of a first alternate sled assembly for the high speed RJ45 jack of  FIG. 47 . 
           [0080]      FIG. 56  is a side view of the contact assembly of  FIG. 55 . 
           [0081]      FIG. 57  is an isometric view of a second alternate sled assembly for the high speed RJ45 jack of  FIG. 47 . 
           [0082]      FIG. 58  is the 3-6 split pair contact assembly for the front sled assembly of  FIG. 57  including PICs, PIC cover and flexible PCB. 
           [0083]      FIG. 59  is an exploded isometric view of the 3-6 split pair PIC assembly of  FIG. 13 . 
           [0084]      FIG. 60  is an isometric view of a flexible PCB for use with the split-pair PIC assembly of  FIG. 59 . 
           [0085]      FIG. 61  is an isometric view of a high speed RJ45 jack with a third alternate front sled assembly. 
           [0086]      FIG. 62  is an isometric view of the third alternate sled assembly for the jack of  FIG. 6I . 
           [0087]      FIG. 63  is an isometric view from the bottom of the front sled assembly of  FIG. 62 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0088]    The present invention is directed to methods and apparatus for reducing crosstalk in electrical connectors. The present invention utilizes crosstalk-reduction principles of U.S. Pat. No. 5,997,358 to Adriaenssens et al., which is incorporated herein by reference in its entirety. The present application further incorporates by reference in its entirety commonly-assigned U.S. Provisional Patent Application No. 60/544,050 entitled “Methods and Apparatus for Reducing Crosstalk in Electrical Connectors,” filed Feb. 12, 2004, and commonly-assigned U.S. patent application Ser. No. 11/055,344, entitled “Methods and Apparatus for Reducing Crosstalk in Electrical Connectors,” filed Feb. 10, 2005. 
         [0089]    Turning now to  FIG. 1 , an exploded view of an electrical jack  10  is shown. Contacts  12  are adapted to make physical and electrical contact with contacts of a plug (not shown in  FIG. 1 ) and further to make electrical contact with a flexible printed circuit (FPC)  14 . The contacts  12  are mechanically mounted in a contact sled  16  and the contact-and-sled assembly is adapted for insertion into a main jack housing  18 . 
         [0090]    In the embodiment shown in  FIG. 1 , the FPC  14  has a rigid extension  20  adapted for accepting insulation displacement connectors (IDCs)  22 . According to one embodiment of the present invention, the rigid extension  20  is an integral end portion of the FPC. The IDCs  22  extend through a rear housing  24  and make physical and electrical contact with conductors  26 . In the embodiment of  FIG. 1 , eight conductors  26  are provided in four pairs. A termination cap  28  encloses the connections between the IDCs  22  and the conductors  26 . Other styles of terminations, such as punch-down style terminations, may also be used with the present invention. 
         [0091]    Turning now to  FIG. 2 , an exploded view of a contact assembly shows the connection between the contacts  12  and the FPC  14  at jack contact points  30  of the FPC  14 . The mechanical and electrical connection between the FPC  14  and the contacts  12  is directly under the plug/jack interface  31 . The jack contact points  30  of the FPC  14  are preferably attached to the contacts  12  opposite a plug/jack interface by electrical resistance welding of solder rivets. The jack contacts  12  are relatively short and they do not conduct signal current down their length. The IDCs  22  extend through the rigid extension  20  of the FPC  14  into IDC sockets  32  of the FPC  14 .  FIG. 3  is a back perspective view of the contact assembly of  FIG. 2  showing the jack contact points  30  of the FPC contacting the contacts  12  and further showing the IDCs  22  extending from the rigid extension  20  of the FPC  14 . 
         [0092]    FPCs according to the present invention may be positioned in a variety of ways. For example,  FIGS. 4 and 5  are side cutaway views showing two configurations of an FPC  14  in electrical jacks. In  FIG. 4 , the FPC  14  is placed such that the jack contact points  30  of the FPC  14  bend toward the rear of the electrical jack  10 . This is the configuration shown in  FIG. 1 .  FIG. 5  shows an alternative configuration in which a forward bend  34  is provided in the FPC  14  such that the jack contact points  30  bend toward the front of the alternative electrical jack  36 . In  FIGS. 4 and 5 , the jack contact points  30  of the FPC  14  contact the contacts  12  of the jacks directly under the plug/jack interface  31 . 
         [0093]    Turning now to  FIG. 6 , a plan view of an FPC  114  according to one embodiment of the present invention is shown. Jack contact points  130  include solder rivets  131  for electrical resistance welding to jack contacts. The jack contact points  130  are numbered one through eight to correspond to eight conductors (provided in four pairs), and IDC sockets  132  are numbered correspondingly. Conductive traces  138  are provided on the FPC  114 . The FPC  114  is adapted for use in a “horizontal extension” embodiment of a jack as shown in  FIGS. 18-22 . 
         [0094]    The FPC  114  electrically connects each jack contact to an IDC and it provides compensation for the crosstalk couplings of a specification plug. It utilizes the teachings of U.S. Pat. No. 5,997,358 to provide said compensation. The FPC  114  is divided into zones as shown in  FIG. 6 . 
         [0095]    The critical pair compensation is for conductor pairs  3 , 6  to  4 , 5  as shown in  FIG. 6 . The zone descriptions below pertain to these pairs and the following statements regarding couplings pertain to couplings between these pairs. The regions of Zones A, B, C, D, E, and F are shown in  FIG. 6  with dotted boxes and plan views of the conductive traces in Zones A-F are shown in  FIGS. 6A-6F , respectively. 
         [0096]    Zone A is a transition zone from the connection to the jack contacts  112  (shown in  FIG. 18 ) to the near-end crosstalk (NEXT) compensation zone. 
         [0097]    Zone B is the NEXT compensation zone. 
         [0098]    Zone C is a transition zone from the NEXT compensation zone to the NEXT crosstalk zone. The design objectives of this zone are to make its inductive and capacitive couplings and the length of the circuit paths equal to those of Zone A. 
         [0099]    Zone E is the NEXT crosstalk zone. 
         [0100]    Zone F is a neutral zone which connects the NEXT crosstalk zone to the IDC sockets  32 . 
         [0101]    The magnitude of the total crosstalk coupling of the NEXT crosstalk zone is approximately equal to that of a specification plug. 
         [0102]    The magnitude of the total compensation coupling of the NEXT compensation zone is slightly less than twice the crosstalk coupling of a specification plug plus twice the total coupling of Zone A. 
         [0103]    All the above Zones A-C, E, and F have distributed couplings and no remote couplings. 
         [0104]    The phase angle change between the effective center of couplings of a specification plug and the center of the NEXT compensation zone is approximately equal to the phase angle change between the center of the NEXT crosstalk zone and the NEXT compensation zone. 
         [0105]    The combination of the jack and a specification plug is therefore symmetrical about the center of the NEXT compensation zone. 
         [0106]    The result of the above is that Forward NEXT is equal to Reverse NEXT. 
         [0107]    Since the NEXT compensation zone is connected to the plug/jack interface by short circuit paths in the FPC, the phase angle change between them is minimized and the change in compensation vs. frequency is minimized. 
         [0108]    The total inductive coupling of the NEXT compensation zone is approximately equal to the total inductive couplings of the balance of the circuit path of the jack and a specification plug. The result is a very low FEXT. 
         [0109]    The flexibility of the FPC allows it to be connected to all the jack contacts which do not move exactly in unison when a plug is installed. It also facilitates connection to various orientations of IDCs or to a printed circuit board (PCB). The relatively thin dielectric layer of the FPC as compared to that of a PCB facilitates a high density of inductive and capacitive couplings which facilitates a relatively short NEXT compensation zone. 
         [0110]    The length of the NEXT compensation zone is preferably approximately equal to the length of the NEXT crosstalk zone. The result is that variations in FPC trace width, which tend to be consistent on an individual FPC, change the capacitive coupling of the NEXT compensation zone and the NEXT crosstalk zone by approximately the same magnitude. This minimizes the compensation variation due to trace width variation. 
         [0111]    Zone D is a compensation zone to compensate for the jack contacts. It provides remote capacitive coupling which is connected close to the plug/jack interface. 
         [0112]    The circuit paths for pairs  1 , 2  &amp;  7 , 8  as shown in  FIG. 6  illustrate one way in which compensation between these pair combinations can be attained. The required compensation for these other pairs is much more easily attained than that for pairs  3 , 6  to  4 , 5 . 
         [0113]      FIGS. 6H-6O  respectively show conductive traces associated with conductors  1 - 8 , with traces on an upper level of the FPC  114  shown in solid lines and traces on a lower level of the FPC  114  shown in dashed lines. Vias  117  are conductive routes from the upper level to the lower level of the FPC  114 . The lengths of conductive traces for pairs  3 ,  6  and  4 ,  5  are approximately equal. 
         [0114]    Turning now to  FIG. 7 , a cross-sectional view along the line A-A of  FIG. 6G , shows cross-sections of the jack contact points  130  of the FPC  114 . Similarly,  FIG. 8A  is a cross-sectional view along the line B-B of  FIG. 6G .  FIG. 8B  is a cross-sectional view along the line C-C of  FIG. 6G . 
         [0115]      FIG. 9  is a cross-sectional view along the line D-D of  FIG. 6G . 
         [0116]      FIG. 10A  is a cross-sectional view along the line E-E of  FIG. 6G . 
         [0117]      FIG. 10B  is a cross-sectional view along the line F-F of  FIG. 6G . 
         [0118]      FIG. 11  is a cross-sectional view along the line G-G of  FIG. 6G . 
         [0119]      FIG. 12  is a cross-sectional view along the line H-H of  FIG. 6G . 
         [0120]      FIG. 13  is a cross-sectional view along the line I-I of  FIG. 6G . 
         [0121]    The numbers one through eight associated with the conductive traces in  FIGS. 7-13  show that the referenced conductive traces correspond to the jack contact points  130  of the FPC  114  and, in turn, with the corresponding conductors to which the jack is connected. 
         [0122]      FIGS. 14-17  are, respectively, detail views of detail areas J, K, L, and M of  FIG. 6G . Dimensions shown in  FIGS. 6G and 7-17  are in inches and are provided for illustration of one particular embodiment of the present invention. It is to be understood that embodiments having different dimensions are contemplated as falling within the scope of the present invention. 
         [0123]    Turning now to  FIG. 18 , a cross-sectional view of a jack  110  having a horizontal extension  120  of the FPC  114  is shown. As with the embodiment of  FIG. 1 , the contacts  112  make electrical and mechanical contact with the FPC  114  and the plug-jack interface  131  is disposed directly above the contact between the contacts  112  and the FPC  114 . IDCs  122  are inserted into IDC sockets of the horizontal extension  120  of the FPC  114 . Other styles of terminations, such as punch-down terminations, may also be used with the present invention. 
         [0124]      FIG. 19  is an exploded view of the jack  110 . A main jack housing  118  is adapted to hold a sled  116  with contacts  112  mounted therein. An IDC block assembly  115  is attached to a rear housing  124  and a termination cap  128  is provided at the rear of the jack  110 . The extension  120  of the FPC  114  is disposed horizontally to accept IDCs  122 .  FIG. 20  is a detail view of the detail N of  FIG. 19  showing the FPC  114  making electrical and mechanical contact with the contacts  112  and further showing IDC sockets  132  adapted to connect to IDCs  122 . 
         [0125]      FIGS. 21, 21A, and 22  are perspective views showing the housing  124 , the IDC block assembly  115 , the contacts  112 , and the FPC  114  with its horizontally-oriented rigid extension  120 . In an alternative embodiment, as shown in  FIG. 21A , one or more pairs of IDCs  122  may be provided with crossover stems  123  in the IDC block assembly  115 . 
         [0126]    According to one embodiment of the present invention, illustrated in  FIG. 23 , IDCs  122  are provided with stems  134 , with some stems  134  incorporating crossovers  136 .  FIG. 23  is a perspective view showing IDCs  122   a - h  corresponding, respectively, to first through eighth conductors of a jack. First through eighth stems  134   a - h  correspond respectively to first through eighth IDCs  122   a - h . First and second stems  134   a  and  134   b  cross over each other at a first crossover  136   a , and fourth and fifth stems  134   d  and  134   e  cross over each other at a second crossover  136   b.    
         [0127]      FIG. 24  is a top view of the first, second, seventh, and eighth IDCs  122   a ,  122   b ,  122   g  and  122   h  showing the first crossover  136   a  in the first and second stems  134   a  and  134   b.    
         [0128]      FIG. 25  is a front view of the IDCs  122   a - h  and their associated stems  134   a - h  showing first and second crossovers  136   a  and  136   b .  FIG. 26  is a rear view of the IDCs  122   a - h  showing the features of  FIG. 25 . 
         [0129]      FIG. 27  is a side view of the embodiment of  FIG. 23  showing IDCs and associated stems. The first crossover  136   a  between first and second stems  134   a  and  134   b  is shown.  FIG. 28  is a view of the detail O of  FIG. 27  showing the first crossover  136   a .  FIG. 29  is a view of the detail P of  FIG. 27  showing the third and sixth stems  134   c  and  134   f .  FIG. 30  is a sectional view of the section Q-Q of  FIG. 27 , showing third, fourth, fifth, and sixth IDCs  122   c - f  with their associated stems  134   c - f  and further showing the second crossover  136   b  between the fourth and fifth stems  134   d  and  134   e . Sections of the first, second, seventh, and eighth stems  134   a ,  134   b ,  134   g , and  134   h  are also shown in  FIG. 30 . 
         [0130]      FIG. 31  is a plan view of an alternative FPC  200 , which may be used with the jack shown in  FIGS. 33-45 . Jack contact points  230  include vias (plated through holes)  231  for electrical connection to jack contacts. The jack contact points  230  correspond to eight conductors (provided in four pairs). Only four (conductors  3 ,  4 ,  5 , and  6 ) are shown in  FIG. 31 . Conductive traces  238  are provided on the FPC  200 . The FPC  200  is adapted for use in a “vertical extension” embodiment of a jack as shown in  FIGS. 33-45 . 
         [0131]    The FPC  200  electrically connects each jack contact to an IDC and it provides compensation for the crosstalk couplings of a specification plug. It utilizes the teachings of U.S. Pat. No. 5,997,358 to provide said compensation. The FPC  200  is divided into zones as shown in  FIG. 31 . 
         [0132]    The critical pair compensation is for conductor pairs  3 , 6  to  4 , 5  as shown in  FIG. 31 . The zone descriptions below pertain to these pairs and the following statements regarding couplings pertain to couplings between these pairs. The regions of Zones A, B, C, D, and E are shown in  FIG. 31 . These Zones are identified below, but the functions are described above, with reference to  FIGS. 6-17 . 
         [0133]    Zone A is a transition zone from the connection to the jack contacts to the near-end crosstalk (NEXT) compensation zone. 
         [0134]    Zone B is the NEXT compensation zone. As illustrated, it includes an optional variable capacitance  250  (described below, with reference to  FIG. 32 ). 
         [0135]    Zone C is a transition zone from the NEXT compensation zone to the NEXT crosstalk zone. The design objectives of this zone are to make its inductive and capacitive couplings and the length of the circuit paths equal to those of Zone A. 
         [0136]    Zone E is the NEXT crosstalk zone. 
         [0137]    The traces below Zone E in  FIG. 31  make up a neutral zone that connects the NEXT crosstalk zone (Zone E) to the IDC sockets. 
         [0138]      FIG. 32  is a perspective view of the variable capacitance  250  shown in  FIG. 31 . The variable capacitance  250  provides a capacitive coupling that effectively decreases as frequency increases.  FIG. 32  is an upper perspective view of this portion showing the capacitive plates, with the substrate removed for ease of illustration. In general, the distributed coupling of the compensation zone would be reduced by the magnitude of capacitive change of the remote coupling of variable capacitance  250 . The technology of the variable capacitive coupling is described in U.S. patent application Ser. No. 60/559,846, entitled “Electrical Connector with Improved Crosstalk Compensation,” filed on Apr. 6, 2004 and incorporated herein by reference in its entirety. 
         [0139]      FIGS. 33-45  are various views of an illustrative embodiment of the present invention, in which alternating-length contacts include integral spring clips for connecting to a flexible printed circuit (FPC).  FIGS. 33-35  are side cutaway views of a portion of such a jack.  FIGS. 36 and 39  are exploded perspective views of a complete jack.  FIGS. 37, 38, and 40-42  are detailed perspective views of components of the jack.  FIGS. 43-45  show details of the jack contacts (also known as plug interface contacts). 
         [0140]    The jack  300  includes a housing  302  that includes an integral front comb  304  and “sandwich-style” contact mounts  306  to hold and position a plurality of contacts  308 . The front comb  304  limits the upward travel of the contacts  308 . Each of the contacts  308  has a corresponding rear contact guide  310  into which the contacts  308  may travel upon insertion of a plug (not shown) into the jack  300 . A FPC  312  is electrically and mechanically connected at one end to a printed circuit board (PCB)  314 , which further connects to IDCs  316  that connect to a network cable (not shown). A second end of the FPC  312  is connected to the contacts  308  by a plurality of spring contacts  318 . Each of the spring contacts  318  is preferably s-shaped to securely hold the FPC  312  so that a good electrical connection is maintained between the contacts  308  and the FPC  312 . The jack further includes a bottom mounting plate  320  for mounting a front sled (around which contacts  308  are placed) in the housing  302 . A rear sled  324  mechanically connects the housing (and components housed therein) to a wire cap  326  designed to accept a network cable for placement of individual wires (not shown) in the IDCs  316 . In the particular wire cap  326  shown, a strain relief clip  328  securely holds the network cable in place, lessening strain on the individual wires within the network cable. The particular arrangement of the rear sled  324 , wire cap  326 , and strain relief clip  328  is shown as an example only. Many other designs could also be used, including those for a punch-down jack. 
         [0141]    An advantageous feature of the jack  300  described with reference to  FIGS. 33-45  is the use of contacts  308  having alternating lengths. As shown in  FIGS. 43-45 , half of the contacts  308   a  are longer in length than the other half  308   b . While the spring contacts  318  on each contact  308  are aligned with one another, the lower portions that wrap around the front sled  322  for mounting in the contact mounts  306  substantially alternate from one end of the front sled  322  to the other. The middle two contacts  308  are the only two neighboring contacts  308  that have the same length, in the preferred embodiment. The difference in length between neighboring contacts  308   a  and  308   b  results in the contacts  308   a  and  308   b  being situated at different locations in relation to one another. This, in turn, reduces the capacitive couplings between contact pairs, which reduces crosstalk. To accommodate the different contacts  308   a  and  308   b , the front comb  304  and front sled  322  are designed for both lengths of contacts. 
         [0142]    Another feature of the design of contacts  308  is that those corresponding to wires  1  and  8  (the outside contacts) are both of the longer length. This helps to accommodate both 8-position plugs (in which contacts  1  and  8  make electrical connection with corresponding contacts in the plug) and 6-position plugs (in which contacts  1  and  8  are pushed down by a solid plastic portion that is common on most 6-position plugs). See  FIG. 34  for an illustration of contact  1  or  8  with a 6-position plug inserted. 
         [0143]    The spring contacts  308  provide an alternative FPC connecting mechanism to that described in other embodiments set forth herein (i.e. welding, etc.). During manufacture (or installation) the FPC  312  may be inserted into some or all of the spring contacts  318 . The spring contacts  318  provide a holding force that pinches the FPC to hold it in place to allow a good electrical connection. 
         [0144]    The disclosed invention provides an electrical connector employing crosstalk-reduction techniques. It should be noted that the above-described and illustrated embodiments and preferred embodiments of the invention are not an exhaustive listing of the forms such the invention might take; rather, they serve as exemplary and illustrative embodiments of the invention as presently understood. By way of example, and without limitation, the jack  110  of  FIGS. 18-22  may be manufactured with a forward bend in the FPC  114 , similar to the forward bend  34  shown in  FIG. 5 . 
         [0145]    One advantage of the present invention is that by having the signal perpetuate generally orthogonal to the plug interface contacts through the flexible printed circuit board, a shorter distance to compensation is enabled. 
         [0146]    Another embodiment is an RJ45 network jack in which the plug interface contact (PIC) interface for contacts  3  and  6  is formed using a thin layer of contact material that is electrically insulated and wrapped over conductive mechanical spring contact that is connected to contact  6  and  3  respectively. The spring contact support at PIC position  3  is electrically connected to PIC interface  6  and spring contact support at position  6  is electrically connected to PIC interface  3 . The PIC interface connection to spring contact is made such that it does not interfere with the plug mating. Reduced PIC interface thickness at position  3  and  6  reduces 2-3, 3-4, 5-6 and 6-7 crosstalk. PIC position  3  and  6  supports having connected to position  6  and  3  respectively, provides crosstalk compensation 2-6, 4-6, 3-5, and 3-7 close to the plug/jack mating interface. 
         [0147]      FIG. 46  illustrates a communication system  430  which includes patch panel  432  with jacks  434  and corresponding plugs  436 . Respective cables  440  are terminated to jacks  434 , and respective cables  438  are terminated to plugs  436 . Once a plug  436  mates with a jack  434 , data can flow in both directions through these connectors. Although communication system  430  is illustrated as a patch panel in  FIG. 46 , alternatively it can be other active or passive equipment. Examples of passive equipment can be, but are not limited to, modular patch panels, punch-down patch panels, coupler patch panels, wall jacks, etc. Examples of active equipment can be, but are not limited to, Ethernet switches, routers, servers, physical layer management systems, and power-over-Ethernet equipment as can be found in data centers and or telecommunications rooms; security devices (cameras and other sensors, etc.) and door access equipment; and telephones, computers, fax machines, printers, and other peripherals as can be found in workstation areas. Communication system  30  can further include cabinets, racks, cable management, and overhead routing systems, and other such equipment. 
         [0148]      FIG. 47  illustrates network jack  434  mated with RJ45 plug  436 . Note that in  FIG. 2  the orientation of network jack  434  and RJ45 plug  436  is rotated 180° about the central axis of cable  440  as compared to the orientation from  FIG. 46 . 
         [0149]    Referring now to  FIG. 48 , network jack  434  includes front housing  442 , front sled assembly  460 , PCB  444 , insulation displacement contact (IDC) support  446 , IDCs  448 , rear housing  450 , and wire cap  452 . Jack  434  can additionally include an alien crosstalk reducing foil as described in U.S. Pat. No. 8,167,661 which is herein incorporated by reference in its entirety. 
         [0150]      FIG. 49  is a rotated isometric view of front sled assembly  460 . It includes PICs  468   1  through  468   8 , PIC covers  462   3  and  462   6 , insulator  466 , and sled  470 . The subscript numbers of PICs and PIC covers represent RJ45 pin positions as defined by ANSI/TIA-568-C.2. PIC covers  462   3  and  462   6  interface with plug contacts electrically. PICs  468   6  and  468   3  provide mechanical support at PIC positions  462   3  and  462   6 , respectively. Insulator  466  electrically isolates PIC covers  462   3  and  462   6  from PICs  468   6  and  468   3 , respectively. PIC cover  462   3  electrically connects to PIC  468   3  at location  474 . PIC Cover  462   6  electrically connects to PIC  468   6  at location  472 . 
         [0151]      FIG. 50  is an exploded view of sled assembly  460  with PICs  468 , PIC covers  462 , insulator  466 , and sled  470 . 
         [0152]      FIG. 51  is a cross-sectional view of a mated plug  436  and jack  434  taken about section line “ 51 - 51 ” in  FIG. 47 . It illustrates plug contact  540 , PIC  468 , and PIC cover  462  in a mated position. Insulator  466  electrically isolates PIC cover  462  from PIC  468  at contact positions  3  and  6 . 
         [0153]      FIG. 52  is an isometric view of sled assembly  460  showing signal path  480  (bold dashed line) for contact position  6  and signal path  482  (bold dotted line) for contact position  3  from plug mating point shown by line  484 . Sled  470  is shown as a dashed outline for reference. For contact position  3 , PIC cover  462   3  electrically connects to plug contact  3  and to PIC  468   3  at location  474 . PIC cover  462   3  is mechanically connected to (but electrically insulated from) PIC  468   6 . PIC  468   6  provides spring force to PIC Cover  462   3  at the plug contact interface. PIC  468   6  is located between PIC  468   2  and  468   4  and provides compensating crosstalk coupling 2-6 and 4-6. The relatively small cross section of PIC cover  462   3  reduces 2-3 and 3-4 crosstalk due to its coupling with  468   2  and  468   4 . Similarly, for contact position  6 , PIC cover  462   6  electrically connects to plug contact  6  and to PIC  468   6  at location  472 . PIC cover  462   6  is mechanically connected to (but electrically insulated from) PIC  468   3 . PIC  468   3  provides spring force to PIC Cover  462   6  at the plug contact interface. PIC  468   3  is located between PIC  468   7  and  468   5  and provides compensating crosstalk coupling 3-7 and 3-5. The relatively small cross section of PIC cover  462   6  reduces 5-6 and 6-7 crosstalk due to its coupling with  468   5  and  468   7 . In addition, PIC cover  462   3  coupling with PIC  468   6  and PIC cover  462   6  coupling with PIC  468   3  helps to offset the impedance mismatch due to the 3-6 pair split, resulting in improved return loss performance. 
         [0154]      FIG. 53 . is an isometric view of sled assembly  460  looking from the bottom. It shows contact  468   3  and  468   6  with tuning lengths  494 ,  496  and  490 ,  492  respectively. Tuning length can be optimized in width and/or length to have desired compensation coupling. 
         [0155]      FIG. 54  illustrates sled assembly  460  in side view. 
         [0156]    Insulator  466  can be a nonconductive label applied with adhesive and/or heat or other insulating coatings including but not limited to polymer and conformal coatings. 
         [0157]    In a second embodiment of the present invention, an alternate sled assembly  500  (shown in  FIGS. 55 and 56 ) PIC covers  512   3  and  512   6  extend under PICS  468   4  and  468   5  to be electrically connected on bottom face of the PIC  468   3  and  468   6 , respectively. PIC cover  512   3  is connected at location  514  and PIC cover  512   6  is connected at  516 . 
         [0158]    In a third embodiment of the present invention, an alternate sled assembly  580  (shown in  FIGS. 57 to 60 ) contains PIC covers  582   3  and  582   6  that are electrically isolated from supporting PICs  518   4  by flexible PCB  588 . Flexible PCB trace  590  ( FIG. 60 ) connects PIC cover  582   6  to PIC  584   6  electrically at contact points  592  and  594  respectively. Flexible PCB trace  596  connects PIC cover  582   3  to PIC  584   3  electrically at contact points  600  and  598  respectively. Traces  590  and  596  are covered with insulating cover lay between lines  602  and  604 . Flexible PCB allows PIC cover and PIC connection path to be brought closer to the plug/jack mating interface. 
         [0159]    In a fourth embodiment (shown in  FIGS. 61 to 63 ) jack  550  includes sled assembly  552  with sled  554 , PICs  556 , PIC covers  558  and insulator  560 . In this embodiment PIC covers  558  interface plug contacts at positions  1 ,  2 ,  4 ,  5 ,  7  and  8 . PIC covers  558   1 ,  158   2 ,  558   4 ,  558   5 ,  558   7 ,  558   8  are mechanically supported but electrically isolated from PICs  556   2 ,  556   1 ,  556   5 ,  556   4 ,  556   8  and  556   7  respectively to provide spring force. PIC cover  558   1  connects to PIC  556   1  at  562 , PIC cover  558   2  connects to PIC  556   2  at  564 , PIC cover  558   4  connects to PIC  556   4  at  566 , PIC cover  558   5  connects to PIC  556   5  at  568 , PIC cover  558   7  connects to PIC  556   7  at  570 , PIC cover  558   8  connects to PIC  556   8  at  572 . PICs  556   3  and  556   6  position relative to  556   1 ,  556   4 ,  556   5  and  556   7  provide compensating coupling 1-3, 3-5, 4-6 and 6-8 while reducing PIC crosstalk coupling 2-3, 3-4, 5-6 and 6-7. 
         [0160]    While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing without departing from the spirit and scope of the invention as described.