Patent Publication Number: US-7914346-B2

Title: Communications jacks having contact wire configurations that provide crosstalk compensation

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §120 as a continuation-in-part application from U.S. patent application Ser. No. 12/264,498, filed Nov. 4, 2008 now U.S. Pat. No. 7,682,203, the disclosure of which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to communications connectors and, more particularly, to crosstalk compensation in communications jacks. 
     BACKGROUND 
     In an electrical communications system, it is sometimes advantageous to transmit information signals (e.g., video, audio, data) over a pair of conductors (hereinafter “wire pair” or “conductor pair” or “differential pair”) rather than over a single conductor. The conductors may comprise, for example, wires, contacts, wiring board traces, conductive vias, other electrically conductive elements and/or combinations thereof. The signals transmitted on each conductor of the differential pair have equal magnitudes, but opposite phases, and the information signal is embedded as the voltage difference between the signals carried on the two conductors. This transmission technique is generally referred to as “balanced” transmission. 
     When a signal is transmitted over a conductor, electrical noise from external sources such as lightning, electronic equipment and devices, automobile spark plugs, radio stations, etc. may be picked up by the conductor, degrading the quality of the signal carried by the conductor. With balanced transmission techniques, each conductor in a differential pair often picks up approximately the same amount of noise from these external sources. Because approximately an equal amount of noise is added to the signals carried by both conductors of the differential pair, the information signal is typically not disturbed, as the information signal is extracted by taking the difference of the signals carried on the two conductors of the differential pair, and thus the noise signal may be substantially cancelled out by the subtraction process. 
     Many communications systems include a plurality of differential pairs. For example, the typical telephone line includes two differential pairs (i.e., a total of four conductors). Similarly, high speed communications systems that are used to connect computers and/or other processing devices to local area networks and/or to external networks such as the Internet typically include four differential pairs. In such systems, channels are formed by cascading plugs, jacks and cable segments (herein, a “channel” refers to the end-to-end connection for the four differential pairs that connect one end device to another end device). In these channels, when a plug mates with a jack, the proximities and routings of the conductors and contacting structures within the jack and/or plug can produce capacitive and/or inductive couplings. Moreover, in the cable segments of these channels four differential pairs are usually bundled together within a single cable, and thus additional capacitive and/or inductive coupling may occur between the differential pairs in each cable. These capacitive and inductive couplings give rise to another type of noise that is called “crosstalk.” 
     “Crosstalk” in a communication system refers to an unwanted signal that appears on the conductors of an “idle” or “victim” differential pair that is induced by a disturbing differential pair. “Crosstalk” includes both near-end crosstalk, or “NEXT”, which is the crosstalk measured at an input location corresponding to a source at the same location (i.e., crosstalk whose induced voltage signal travels in an opposite direction to that of an originating, disturbing signal in a different path), as well as far-end crosstalk, or “FEXT”, which is the crosstalk measured at the output location corresponding to a source at the input location (i.e., crosstalk whose signal travels in the same direction as the disturbing signal in the different path). Both NEXT and FEXT are undesirable signals that interfere with the information signal. 
     A “disturbing” differential pair may impart two different types of crosstalk onto another differential pair. The nature of the induced voltage determines which of two types of crosstalk is occurring. The first of these two types of crosstalk is referred to as differential-to-differential crosstalk (XTLK DD ). It occurs when the induced voltages from the source differential pair that are imparted on both the conductors of the victim differential pair are unequal. Differential-to-differential crosstalk is measured as the ratio of the induced differential voltage on the victim pair to the source or driven differential voltage on the disturbing pair (typically referenced as 1 volt). Differential voltage is defined as the difference between the voltages on the two conductors of the differential pair, i.e., V diff =(V 1 -V 2 , where V 1  is the voltage on conductor  1  and V 2  is the voltage on conductor  2  of the differential pair. Differential-to-differential crosstalk is typically expressed in decibels (dBs) and can be defined as:
 
 XTLK   DD =20 log(V 1 -V 2 )
 
where V 1  is the induced voltage on conductor  1  of the victim pair and V 2  is the induced voltage on conductor  2  of the victim pair.
 
     The second of the two types of crosstalk is referred to as differential-to-common mode crosstalk (XTLK DC ). Differential-to-common mode crosstalk occurs when the induced voltage is common to both conductors of the victim differential pair, and hence the victim pair can be viewed as being a single conductor. The voltage that is common to both conductors is called the common mode voltage (V CM ) and is expressed as the average voltage on the two conductors of the differential pair, i.e., V CM =(V 1 +V 2 )/2. Differential-to-common mode crosstalk is measured as the ratio of the induced common mode voltage on the victim differential pair to the source or driven differential voltage of the disturbing pair. It is also expressed in dBs as:
 
 XTLK   DC =20 log(( V   1   +V   2 )/2)
 
where V 1  and V 2  are as described above. Note that the voltages V 1  and V 2  can be calculated from the inductive and capacitive coupling parameters between disturbing and victim conductors. Further note that if V 1 =−V 2 , then V CM =0 and differential-to-common mode crosstalk is zero. Under this condition, the circuits are considered balanced. This is a desirable condition to minimize a type of crosstalk known as “alien NEXT” (which is described in more detail herein) in the channel.
 
     A variety of techniques may be used to reduce crosstalk in communications systems such as, for example, tightly twisting the paired conductors (which are typically insulated copper wires) in a cable, whereby different pairs are twisted at different rates that are not harmonically related, so that each conductor in the cable picks up approximately equal amounts of signal energy from the two conductors of each of the other differential pairs included in the cable. If this condition can be maintained, then the crosstalk noise may be significantly reduced, as the conductors of each differential pair carry equal magnitude, but opposite phase signals such that the crosstalk added by the two conductors of a differential pair onto the other conductors in the cable tends to cancel out. 
     While such twisting of the conductors and/or various other known techniques may substantially reduce crosstalk in cables, most communications systems include both cables and communications connectors (i.e., jacks and plugs) that interconnect the cables and/or connect the cables to computer hardware. Unfortunately, the jack and plug configurations that were adopted years ago generally did not maintain the conductors of each differential pair a uniform distance from the conductors of the other differential pairs in the connector hardware. Moreover, in order to maintain backward compatibility with connector hardware that is already in place in existing homes and office buildings, the connector configurations have, for the most part, not been changed. As such, the conductors of each differential pair tend to induce unequal amounts of crosstalk on each of the other conductor pairs in current and pre-existing connectors. As a result, many current connector designs generally introduce some amount of NEXT and FEXT crosstalk. 
     Pursuant to certain industry standards (e.g., the TIA/EIA-568-B.2-1 standard approved Jun. 20, 2002 by the Telecommunications Industry Association), each jack, plug and cable segment in a communications system may include a total of eight conductors  1 - 8  that comprise four differential pairs. By convention, the conductors of each differential pair are often referred to as a “tip” conductor and a “ring” conductor. The industry standards specify that, in at least the connection region where the contacts (blades) of a modular plug mate with the contacts of the modular jack (i.e., the plug-jack mating point), the eight conductors are aligned in a row, with the four differential pairs specified as depicted in  FIG. 1 . As known to those of skill in the art, under the TIA/EIA 568, type B configuration, conductor  5  in  FIG. 1  comprises the tip conductor of pair  1 , conductor  4  comprises the ring conductor of pair  1 , conductor  1  comprises the tip conductor of pair  2 , conductor  2  comprises the ring conductor of pair  2 , conductor  3  comprises the tip conductor of pair  3 , conductor  6  comprises the ring conductor of pair  3 , conductor  7  comprises the tip conductor of pair  4 , and conductor  8  comprises the ring conductor of pair  4 . 
     As shown in  FIG. 1 , in the connection region where the contacts (blades) of a modular plug mate with the contacts of the modular jack, the conductors of the differential pairs are not equidistant from the conductors of the other differential pairs. By way of example, conductor  2  (i.e., the ring conductor of pair  2 ) is closer to conductor  3  (i.e., the tip conductor of pair  3 ) than is conductor  1  (i.e., the tip conductor of pair  2 ) to conductor  3 . Consequently, differential capacitive and/or inductive coupling occurs between the conductors of pairs  2  and  3  that generate both NEXT and FEXT. Similar differential coupling occurs with respect to the other differential pairs in the modular plug and the modular jack. 
     U.S. Pat. No. 5,997,358 to Adriaenssens et al. (hereinafter “the &#39;358 patent”) describes multi-stage schemes for compensating NEXT for a plug-jack combination. The entire contents of the &#39;358 patent are hereby incorporated herein by reference as if set forth fully herein. The connectors described in the &#39;358 patent can reduce the “offending” NEXT that may be induced from the conductors of a first differential pair onto the conductors of a second differential pair in, for example, the contact region where the blades of a modular plug mate with the contacts of a modular jack. Pursuant to the teachings of the &#39;358 patent, a “compensating” crosstalk may be deliberately added, usually in the jack, that reduces or substantially cancels the offending crosstalk at the frequencies of interest. The compensating crosstalk can be designed into the lead frame wires of the jack and/or into a printed wiring board that is electrically connected to the lead frame within the jack. As discussed in the &#39;358 patent, two or more stages of NEXT compensation may be provided, where the magnitude and phase of the compensating crosstalk signal induced by each stage, when combined with the compensating crosstalk signals from the other stages, provide a composite compensating crosstalk signal that substantially cancels the offending crosstalk signal over a frequency range of interest. The multi-stage (i.e., two or more) compensation schemes disclosed in the &#39;358 patent can be more efficient at reducing the NEXT than schemes in which the compensation is added at a single stage, especially when the second and subsequent stages of compensation include a time delay that is selected and/or controlled to account for differences in phase between the offending and compensating crosstalk signals. Efficiency of crosstalk compensation is increased if the first stage or a portion of the first stage design is contained in the lead frame wires. 
     Another type of crosstalk that must be considered is “alien” crosstalk and, in particular, alien NEXT. Alien NEXT is the differential crosstalk that occurs between communication channels. Obviously, physical separation between the jacks of the two channels at issue helps reduce alien crosstalk levels, as may some conventional crosstalk compensation techniques. However, a problem case may be “pair  3 ” of one channel crosstalking to “pair  3 ” of another channel, even if the pair  3  plug and jack wires in each channel are remote from each other and the only coupling occurs between the routed cabling. This form of alien NEXT occurs because of pair-to-pair unbalances that exist in the plug-jack combination, which results in mode conversions from differential NEXT to common mode NEXT and vice versa. In particular, differential-to-common mode crosstalk from pair  3  to both pair  2  and pair  4  can contribute to such mode conversion problems. To reduce this form of alien NEXT, shielded systems containing shielded twisted pairs or foiled twisted pair configurations may be used. However, the inclusion of shields can increase cost of the system. Another approach to reduce or minimize alien NEXT utilizes spatial separation of cables within a channel and/or spatial separation between the jacks in a channel. However, this is typically impractical because bundling of cables and patch cords is common practice due to “real estate” constraints and ease of wire management. 
     SUMMARY 
     Embodiments of the present invention can provide communications jacks that include a housing having a plug aperture that is configured to receive a mating plug that is inserted along a horizontal plug axis. The jacks further include a vertically-oriented wiring board that is mounted substantially normal to the horizontal plug axis. A first contact wire and a second contact wire that form a first differential pair of contact wires are provided, each of which have a fixed portion that is mounted in the vertically-oriented wiring board and a deflectable portion that is at least partially positioned in the plug aperture. A third contact wire and a fourth contact wire are provided that form a second differential pair of contact wires, each of which also have a fixed portion that is mounted in the vertically-oriented wiring board and a deflectable portion that is at least partially positioned in the plug aperture. In these jacks, at least a portion of the first differential pair of contact wires is positioned between the contact wires of the second differential pair of contact wires, and the deflectable portions of the third and fourth contact wires include a crossover. Additionally, the fixed portions of the third and fourth contacts are spaced further apart vertically than are the fixed portions of the first and second contacts. 
     In some embodiments, the jacks may also include a fifth contact wire and a sixth contact wire that form a third differential pair of contact wires, and a seventh contact wire and eighth contact wire that form a fourth differential pair of contact wires. In such embodiments, each of the fifth through eighth contact wires includes a fixed portion that is mounted in the vertically-oriented wiring board and a deflectable portion that is at least partially positioned in the plug aperture. In these embodiments, the third contact wire and the fourth contact wire may each include a second fixed portion that is mounted in the vertically-oriented wiring board. The third contact wire and the fourth contact wire may each include a first longitudinal segment that includes the fixed portion, a second longitudinal segment that includes the second fixed portion, a third longitudinal segment that includes a plug contact region that is configured to make electrical contact with a contact of a mating plug, and a transverse segment that connects the first, second and third longitudinal segments. The transverse segment of the third contact wire may cross the first and second contact wires and at least one of the fifth through eighth contact wires, and the transverse segment of the fourth contact wire may cross the first and second contact wires and at least one of the fifth through eighth contact wires. As a non-limiting example, in certain of these embodiments, the first and second contact wires may be contact wires  4  and  5 , respectively, of a TIA/EIA 568 type B jack, the third and fourth contact wires may be contact wires  3  and  6 , respectively, of a TIA/EIA 568 type B jack, the fifth and sixth contact wires may be contact wires  1  and  2 , respectively, of a TIA/EIA 568 type B jack, and the seventh and eighth contact wires may be contact wires  7  and  8 , respectively, of a TIA/EIA 568 type B jack. 
     In some embodiments, the fixed portions of the second, third, fifth and seventh contact wires and the second fixed portion of the third contact wire may be at least generally aligned in a first row, and the fixed portions of the first, fourth, sixth and eighth contact wires and the second fixed portion of the fourth contact wire may be generally aligned in a second row that is below the first row. The second fixed portion of the third contact wire may be on one end of the first row and the second fixed portion of the fourth contact wire may be on one end of the second row. Additionally, the fixed portion and the second fixed portion of the third contact wire may be mounted above the fixed portions of the second and fifth contact wires, and the fixed portion and the second fixed portion of the fourth contact wire may be mounted below the fixed portions of the first, and eighth contact wires. The third differential pair of contact wires and the fourth differential pair of contact wires may also each include a crossover. 
     In some embodiments, the jack may further include a second wiring board that includes a plurality of contact pads. In such embodiments, the deflectable portion of at least some of the first through eighth contact wires may be configured to make physical and electrical contact with respective contact pads when the mating plug is received within the plug aperture. 
     Pursuant to further embodiments of the present invention, communications jacks are provided that include a housing that has a plug aperture that is configured to receive a mating plug that is inserted along a first axis. The jacks also include a wiring board that is mounted substantially perpendicular to the first axis. The jacks further include first through eighth contact wires, each of which has a termination end that is mounted in the wiring board and a free end that includes a plug contact region. Moreover, the third and sixth contact wires also each include a second termination end that is mounted in the wiring board and a crossover segment that connects the first and second termination ends. In these jacks, the fourth and fifth contact wires form a first differential pair of contact wires, the first and second contact wires form a second differential pair of contact wires, the third and sixth contact wires form a third differential pair of contact wires, and the seventh and eighth contact wires form a fourth differential pair of contact wires. Thus, in certain of these embodiments, the first through eighth contact wires may correspond to the first through eighth contact wires, respectively, of a TIA/EIA 568 type B jack. The plug contact regions of the first through eighth contact wires are arranged in a generally side-by-side relationship in numerical order, and the third contact wire crosses at least the fourth, fifth and sixth contact wires, while the sixth contact wire crosses at least the third, fourth and fifth contact wires. 
     In some embodiments, the crossover segment of the third contact wire may be substantially perpendicular to the first termination end of the third contact wire and to the second termination end of the third contact wire. The termination ends of the first, fifth and seventh contact wires and the first and second termination ends of the third contact wire may be generally aligned in a first row, and the termination ends of the second, fourth and eighth contact wires and the first and second termination ends of the sixth contact wire may be generally aligned in a second row that is vertically spaced apart from the first row. 
     In some embodiments, the surface of the wiring board into which the first through fourth contact wires are mounted may define an x-y plane, and the first termination end of the third contact wire and the first termination end of the sixth contact wire may be spaced apart a first distance in the x-direction and a second distance in the y-direction, and the termination end of the fourth contact wire and the termination end of the fifth contact wire may be spaced apart by a third distance in the x-direction and a fourth distance in the y-direction. The first distance may exceed the third distance and the second distance may exceed the fourth distance. Additionally, the second differential pair of contact wires may include a crossover and the fourth differential pair of contact wires may include a crossover. 
     Pursuant to still further embodiments of the present invention, contact wires that are suitable for use in an RJ-45 communications jack are provided. These contact wires include first and second termination ends, each of which have a press-fit termination, a crossover section that connects the first termination end and the second termination end, and a longitudinal segment that includes a free end and a plug contact region that is configured to make physical and electrical contact with a contact of a mating plug connector, the longitudinal segment extending from the crossover section. In some embodiments, the first termination end, the second termination end and the longitudinal segment may be generally parallel to each other. Additionally, the crossover section may be generally perpendicular to the longitudinal segment. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows the modular jack contact wiring assignments for an 8-position communications jack (T568B) as viewed from the front opening of the jack. 
         FIG. 2  is an exploded perspective view of a communications jack according to embodiments of the present invention. 
         FIG. 3  is an enlarged perspective view of the contact wires of the communications jack of  FIG. 2 . 
         FIG. 4  is an enlarged perspective view of one of the contact wires of the communications jack of  FIG. 2 . 
         FIG. 5  is a cross-sectional view of the contact wires of  FIG. 3  taken along the line  5 - 5  of  FIG. 3 . 
         FIG. 6  is a perspective view of the contact wires of  FIG. 3  that shows how the contact wires mate with a mating plug. 
         FIG. 7  is a plan view of the vertically-oriented wiring board of the communications jack of  FIG. 2 . 
         FIG. 8  is a plan view of the horizontally-oriented wiring board of the communications jack of  FIG. 2 . 
         FIG. 9  is an enlarged perspective view of the contact wires of a communications jack according to further embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is described more particularly hereinafter with reference to the accompanying drawings. The invention is not intended to be limited to the illustrated embodiments; rather, these embodiments are intended to fully and completely disclose the invention to those skilled in this art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     As used herein, the terms “attached” or “connected” can mean either a direct or an indirect attachment or connection between elements. In contrast, the terms “directly attached” and “directly connected” refer to a direct attachment and direct connection, respectively, without any intervening elements. 
     This invention is directed to communications connectors, with a primary example of such being a communications jack that includes a plug aperture that receives a mating plug that is inserted along a plug axis. The communications jacks according to embodiments of the present invention may include contact wires that include a crossover in the pair  3  contact wires (as the contact wires are defined in TIA/EIA 568B). These contact wires are mounted on a wiring board that is mounted normal to the plug axis. The contact wires of pairs  1  and  3  may also include a heightened stagger. This heightened stagger may be used to reverse the polarity of the crosstalk between the contact wires of pairs  1  and  3  just outside the plug contact regions of the contact wires and before the crossover in the pair  3  contact wires. As discussed herein, the communications jacks according to embodiments of the present invention can efficiently compensate differential-to-differential crosstalk between pairs  1  and  3 ; pairs  2  and  3 ; and pairs  3  and  4 , while also providing enhanced differential-to-common mode crosstalk compensation on pair  3  to pair  2  and for pair  3  to pair  4 . As discussed above, the differential-to-common mode crosstalk from pair  3  to pairs  2  and  4  can be the most problematic in terms of mode conversion. Thus, the communications jacks according to certain embodiments of the present invention can provide high levels of differential-to-differential crosstalk compensation while also reducing mode conversion and providing enhanced channel performance. 
       FIGS. 2-8  illustrate a communications jack, designated broadly as  10 , according to certain embodiments of the present invention.  FIG. 2  is an exploded perspective view of the communications jack  10 . As shown in  FIG. 2 , the jack  10  includes a jack frame  11  that includes a plug aperture  18  for receiving a mating plug, a cover  19 , a plurality of contact wires which are broadly designated as  20  (designated individually as  20 - 1  through  20 - 8  in  FIGS. 3-5 ), a first, vertically-oriented wiring board  40 , a second, horizontally-oriented wiring board  70 , a plurality of insulation displacement contacts that are broadly designated as  60 , and an IDC cover (not shown in the figures). 
     The jack frame  11  has a front face  12  that includes the plug aperture  18 . The jack frame  11  further includes side walls  13 ,  14 , a bottom wall  15 , a back wall  16  and a comb structure  17  that define the sides, bottom, rear and top, respectively, of the plug aperture  18 . Note that some or all of the walls  13 - 16  may be partial walls. The plug aperture  18  comprises a cavity that is sized and configured to receive a mating communications plug that is inserted into the plug aperture  18  along the plug axis “P” shown in  FIG. 2 . The plug axis P is normal to the front face  12  of the jack frame  11 . Most typically, communications jacks such as the jack depicted in  FIG. 2  are mounted so that the opening to the plug aperture that receives the mating plug defines a vertical plane. Consequently, the plug axis “P” will most typically be a horizontal axis. However, it will be appreciated that the communications jack may be mounted in different orientations such as, for example, rotated ninety degrees so that the opening to the plug aperture defines a horizontal plane. When the communications jack  10  is mounted in this manner, the horizontally-oriented elements in  FIG. 2  will become vertically-oriented elements and vice versa. Thus, it will be appreciated that herein mins such as “horizontally-oriented” and “vertically-oriented” and the like are used to describe the relative orientation of components of the communications jack with respect to each other, and do not limit the present invention to communications jacks that are mounted in a particular orientation. 
     The cover  19  may generally have an “L” shape. The cover  19  extends across the top of the jack frame  11 , and part of the cover  19  may complete the back wall  16  of the jack frame  11 . The jack frame  11 , the cover  19  and the IDC cover (not shown in the figures) together comprise a housing that defines the plug aperture and protects other of the components of the communications jack  10 . The jack frame  11 , the cover  19  and the IDC cover may be made of a suitable insulative plastic material that meets all applicable standards with respect to, for example, electrical breakdown resistance and flammability. Typical materials include, but are not limited to, polycarbonate, ABS, and blends thereof. The jack frame  11 , the cover  19  and the IDC cover may be conventionally formed and hence will not be described in further detail herein. Those skilled in this art will recognize that a wide variety of other configurations of housings may also be employed in embodiments of the present invention, and that the housing may comprise more or less pieces than the exemplary housing illustrated in  FIG. 2 . 
     The contact wires  20  each comprise a conductive element that is used to make physical and electrical contact with a respective contact on a mating communications plug. Typically, the contact wires  20  comprise spring contact wires that are formed of resilient metals such as spring-tempered phosphor bronze, beryllium copper, or the like. A typical cross section of each contact wire  20  is 0.017 inches wide by 0.010 inches thick. As shown in  FIG. 2 , the contact wires  20  are mounted on the first, vertically-oriented wiring board  40  in cantilever fashion so that the contact wires  20  are cantilevered from the rear of the jack  10  toward the front of the jack  10  and extend into the plug aperture  18 . 
       FIG. 3  is an enlarged perspective view of the contact wires  20 - 1  through  20 - 8  that more clearly illustrates the paths traversed by each contact wire.  FIG. 4  is an enlarged perspective view of contact wire  20 - 3 .  FIG. 5  is a cross-sectional view of the contact wires  20  taken along the line  5 - 5  of  FIG. 3 . The contact wires  20  of jack  10  will now be discussed in greater detail with respect to  FIGS. 3-5 . Note that in  FIGS. 3-5  the contact wires  20  have been rotated 180 degrees from their orientation in  FIG. 2 . 
     Turning first to  FIG. 3 , it can be seen that the contact wires  20  (which are individually labeled in  FIGS. 3-5  as contact wires  20 - 1  through  20 - 8 ) are arranged in differential pairs as defined by TIA 568B. In particular, contact wires  20 - 4 ,  20 - 5  form in a first differential pair (pair  1 ) of contact wires that may be used to carry a first differential signal, contact wires  20 - 1 ,  20 - 2  form a second differential pair (pair  2 ) of contact wires that may be used to carry a second differential signal, contact wires  20 - 3 ,  20 - 6  form a third differential pair (pair  3 ) of contact wires that may be used to carry a third differential signal, and contact wires  20 - 7 ,  20 - 8  form a fourth differential pair (pair  4 ) of contact wires that may be used to carry a fourth differential signal. Thus, communication jack  10  may carry up to four differential signals at a time. As shown in  FIG. 3 , contact wires  20 - 4 ,  20 - 5  are in the center positions in the contact wire array, contact wires  20 - 1 ,  20 - 2  are adjacent to each other and occupy the rightmost two positions (from the vantage point of  FIG. 3 ) in the sequence, and contact wires  20 - 7 ,  20 - 8  are adjacent to each other and occupy the leftmost two positions (from the vantage point of  FIG. 3 ) in the sequence. Contact wires  20 - 3 ,  20 - 6  are positioned so that, in the plug contact regions of the contact wires, these contact wires sandwich contact wires  20 - 4  and  20 - 5  (i.e., contact wires  20 - 4  and  20 - 5  are both positioned between contact wires  20 - 3  and  20 - 6  in the plug contact region of the contact wires). 
     Referring now to  FIGS. 2-4  (and, in particular, to  FIG. 4  in which the regions of each contact wire are illustrated on an enlarged depiction of contact wire  20 - 3 ), each of the contact wires  20  has a deflectable portion  21  that extends into the plug aperture  18  and a fixed portion  25  that is mounted in the vertically-oriented wiring board  40 . The deflectable portion  21  of each contact wire  20  refers to the portion of the contact wire  20  that moves when a mating plug is received within the plug aperture  18  so as to come into physical contact with the contact wires  20 . The deflectable portion  21  of each contact wire  20  includes a plug contact region  22  and a free end portion  23 . The deflectable portion  21  of some of the contact wires  20  further includes a crossover section  24  where the contact wire crosses over and/or under one or more of the other contact wires when the contact wires  20  are viewed from above (i.e., when viewed along the vertical axis “C” in  FIG. 2 ). The crossover sections  24  are located in a crossover region  33  of the array of contact wires  20 . Finally, each contact wire  20  includes a termination end  27  that comprises the portion of the contact that extends from the crossover region  33  to the fixed portion  25  of the contact wire that is mounted in the vertically-oriented wiring board  40 . In the particular embodiment of the present invention depicted in  FIGS. 2-8 , the termination end  27  of each contact wire  20  includes the fixed portion  25  of the contact wire and part of the deflectable portion  21  of the contact wire (i.e., the part from the fixed portion  25  up to the crossover region  33 ). As known to those of skill in the art, the set of contact wires  20  are often referred to as a “lead frame.” 
     As noted above, the deflectable portion  21  of each contact wire  20  further includes a plug contact region  22  and a free end  23 . The plug contact region  22  comprises the portion of the contact wire that is configured to make physical contact with a respective one of the contacts (e.g., plug blades) on a mating plug when the mating plug (see  FIG. 6 ) is received within the plug aperture  18  of communications jack  10  along the direction of the horizontal plug axis P (see  FIG. 2 ). Typically, the plug contact regions  22  of all eight contact wires will be aligned in a generally parallel, side-by-side relationship as shown in  FIGS. 2-3  and  6 . The free end  23  refers to the end portion of the contact wire that extends beyond the plug contact region  22 . The free ends  23  of the contact wires  20  extend into individual slots in the comb structure  17 . The free ends  23  of the contact wires  20  may, in some embodiments, be aligned parallel and generally co-planar with one another, as shown in  FIGS. 2-3  and  6 . The free ends  23  may be spaced apart from one another by, for example, 0.04 inches. 
     When a mating plug is received within the plug aperture  18  and communications signals are transmitted through the contact wires  20 , current will flow from the fixed portion  25  of each contact wire  20  to the plug contact region  22  of the contact wire, or current will flow from the mating plug contact, through the plug contact region  22  to the fixed portion  25  of the contact wire  20  (depending upon the direction of travel of the communications signal). However, current will generally not flow forward of the plug contact regions  22  (i.e., into the free end  23  of each contact wire  20 ), as the free end  23  of the contact wire comprises a “dead-end” branch off of its respective signal carrying path through the jack  10 . Consequently, only capacitive coupling (and accompanying crosstalk) is generated between the free ends  23  of the contact wires  20 , whereas rearward of the plug contact regions  22 , both inductive and capacitive coupling/crosstalk will occur. 
     The termination end  27  of each of the contact wires  20  includes a deflectable segment  26  (it will be appreciated that while the deflectable segments  26  of the contact wires depicted in  FIGS. 2-4  and  6  are generally straight, they need not be straight in other embodiments) and the fixed portion  25 . In the particular embodiment of  FIGS. 2-8 , the fixed portion  25  comprises an “eye-of-the-needle” or other press-fit termination that may be inserted into a metal-plated aperture on the vertically-oriented wiring board  40  without the need for a soldered connection. The rear wall  16  of the jack frame  11  includes a plurality of vertical slots. The cover  19  includes mating projections (not visible in  FIG. 2 ) that fill the vertical slots in the rear wall  16 . A portion of the termination end  27  of each contact wire  20  passes through one of the vertical slots in the rear wall  16 , and when the cover  19  is placed on the jack frame  11  the projections thereon capture this portion of the termination end  27  (i.e., the portion just before the press-fit termination) of each contact wire  20  and lock it into place. The press-fit termination of each contact wire  20  passes through an opening between the vertical slot in the rear wall  16  and the corresponding projection on the cover  19  so as to extend outside the rear of jack frame  11  for mating with the vertically-oriented wiring board  40 . 
     As can best be seen in  FIG. 3 , the contact wires  20 - 1 ,  20 - 2  of pair  2 , the contact wires  20 - 3 ,  20 - 6  of pair  3 , and the contact wires  20 - 7 ,  20 - 8  of pair  4  include a respective “crossover.” These crossovers are labeled  30 ,  31 ,  32  in  FIG. 3 . Herein, the term “crossover” is used to refer to a location in which the contact wires of a differential pair of contact wires cross each other without making electrical contact when the contact wires are viewed from the perspective of axis “C” in  FIG. 2  (i.e., when the jack is viewed from either above or below) when the jack is oriented as shown in  FIG. 2 . Crossovers are included to provide compensatory crosstalk between contact wires. Typically, such crossovers are provided so that the contact wires of a differential pair of contact wires trade positions. Thus, in some embodiments, when a differential pair of contact wires includes a crossover, the free end  23  of each contact wire  20  of the pair may be generally aligned longitudinally with the termination end  27  of the other contact wire  20  of the pair. The crossovers  30 ,  31 ,  32  may be located, for example, approximately in the center of their contact wires (between the free ends  23  of the contact wires  20  and their fixed portions  25 ). Each of the crossovers  30 ,  31 ,  32  are located in the deflectable portions  21  of the contact wires  20 . In some embodiments, the crossovers may be located as close to the plug contact regions  22  of the contact wires  20  as possible, in order to limit the degree of offending crosstalk and to generate compensating crosstalk as close as possible to the plug contact region  22  where the offending crosstalk is generated. In the illustrated embodiment, the crossovers  30 ,  32  are implemented via complementary localized bends in the crossing contact wires, with one wire being bent upwardly and the other wire being bent downwardly. The manner in which the crossover  31  on pair  3  is implemented is discussed in more detail below. The presence of a crossover, structural implementations thereof, and its effect on crosstalk are discussed in some detail in the &#39;358 patent described above and U.S. Pat. No. 5,186,647 to Denkmann et al. The contact wires of pair  1  (wires  20 - 4 ,  20 - 5 ) do not include a crossover in the particular embodiment of  FIGS. 2-8 . 
     As shown best in  FIGS. 3-5 , contact wires  20 - 3  and  20 - 6  have a non-traditional shape. In particular, each of these contact wires includes the standard termination end  27  along with a second termination end  28 . Contact wires  20 - 3  and  20 - 6  further each include a crossover section  24  which, in this particular embodiment, is implemented as a transverse segment that connects the standard termination end  27  and the second termination end  28 . Each contact wire  20 - 3 ,  20 - 6  further includes a fourth distinct segment that includes the plug contact region  22  and the free end  23  of the contact wire. 
     As can be seen in  FIGS. 3-4 , a first portion  24 ′ of the crossover section  24  on each of contacts  20 - 3  and  20 - 6  is used to implement the crossover on pair  3 , as the portion  24 ′ effectively allows the contact wires  20 - 3  and  20 - 6  to change positions approximately halfway through the lead frame. A second portion  24 ″ of the crossover section  24  on each of contacts  20 - 3  and  20 - 6  is used to connect to the second termination end  28  of the contact wire. This second termination end  28  may serve multiple functions. First, the second termination  28  end may provide physical support to the contact wire that it is part of in order to enhance the mechanical integrity and stability of the contact wire. This may facilitate ensuring that the first portion  24 ′ of the crossover section  24  does not come into physical contact with any of the other contact wires (and in particular, contact wires  20 - 4  and  20 - 5 ) when a mating plug is inserted into the plug aperture  18 . Additionally, as will be discussed in greater detail below, the second termination end  28  may connect to one or more crosstalk compensation circuits on the vertically-oriented wiring board  40 . Moreover, as discussed in greater detail below, the second termination end  28  of each contact wire  20 - 3 ,  20 - 6  may also capacitively couple with the termination end  27  of at least one adjacent contact wire (e.g., as shown best in  FIG. 5 , the second termination end  28  of contact  20 - 3  couples with the termination end  27  of contact wire  20 - 1  and the second termination end  28  of contact  20 - 6  couples with the termination end  27  of contact wire  20 - 8 ), which can provide additional crosstalk compensation. It will be appreciated, however, that the second termination end  28  need not perform all of these functions. The contact wire configuration of  FIG. 3  enables the commencement of inductive differential-to-differential and differential-to-common mode crosstalk compensation at minimal delay from the corresponding crosstalk sources (i.e., the plug contact region  22  of the contact wires  20  and the mating plug), which can be important to effective crosstalk compensation. 
     As can best be seen in  FIG. 3 , the transverse crossover section  24  provided on each of contact wires  20 - 3 ,  20 - 6  “crosses” a plurality of the other contact wires  20 . In particular, the transverse crossover section  24  of contact wire  20 - 3  crosses contact wires  20 - 1 ,  20 - 4 ,  20 - 5  and  20 - 6 , and the transverse crossover section  24  of contact wire  20 - 6  crosses contact wires  20 - 3 ,  20 - 4 ,  20 - 5  and  20 - 8 . Herein, the terms “cross” and “crosses” are used to refer to a first contact wire passing from one side to the other side of a second contact wire (i.e., either over or under) without making electrical contact when the first and second contact wires are viewed from the perspective of axis “C” in  FIG. 2  (i.e., when the jack is viewed from either above or below). Thus, when the two contact wires of a differential pair cross, a crossover is formed. 
     Note that in  FIG. 3 , the various elements/portions of each contact wire (e.g., fixed portion  25 ) have only been designated on an exemplary one of the eight contact wires. It will be appreciated that each of the eight contact wires include each identified element/portion, except that only six of the contact wires ( 20 - 1 ,  20 - 2 ,  20 - 3 ,  20 - 6 ,  20 - 7 ,  20 - 8 ) include the crossover  24 , and only two of the contact wires ( 20 - 3 ,  2 - 6 ) include the second termination ends  28 . Each portion/element of each contact wire is not individually labeled in  FIG. 3  in order to simplify  FIG. 3 . 
       FIG. 5  is a cross-sectional view of the contact wires of  FIG. 3  taken along the line  5 - 5  of  FIG. 3 , which shows the relative positions of the contact wires  20  as they enter the vertically-oriented wiring board  40 . The individual contact wires  20  separate from each other vertically to varying degrees as the contact wires approach the wiring board  40 . As is apparent from  FIGS. 3 and 5 , the contact wires  20  include an exaggerated vertical stagger. As can be seen, for example, in  FIGS. 2 and 5 , the front face of the vertically-oriented wiring board  40  (i.e., the surface into which the contact wires  20  are mounted) defines a vertically oriented plane. In  FIG. 5 , an x-y axis has been superimposed on the wiring board  40 , where the x-axis is a horizontal axis and the y-axis is a vertical axis. The term “vertical stagger” is used herein to refer to the distance between portions of the contact wires  20  of a pair in the y-direction of  FIG. 5 . 
     As shown in  FIG. 3 , the vertical stagger in the contact wires  20  starts between the plug contact regions  22  of the contact wires  20  and the crossover section  24  of the contact wires  20 . As shown in  FIG. 5 , the contact wires of pair  3  ( 20 - 3  and  20 - 6 ) have the largest vertical stagger (i.e., are separated by the largest distance in the y-direction), while the contact wires of pair  1  ( 20 - 4  and  20 - 5 ) have the smallest vertical stagger, which facilitates implementing the pair  3  crossover without short-circuiting any of the contact wires  20 - 3  through  20 - 6 . 
     As can best be seen in  FIG. 5 , as a result of the vertical stagger, the termination ends  27 ,  28  of the contact wires  20  are generally aligned in two rows on the vertically-oriented wiring board  40 . The top row includes the termination ends  27  of contact wires  20 - 1 ,  20 - 3 ,  20 - 5  and  20 - 7  and the second termination end  28  of contact wire  20 - 3 . The bottom row includes the termination ends  27  of contact wires  20 - 2 ,  20 - 4 ,  20 - 6  and  20 - 8  and the second termination end  28  of contact wire  20 - 6 . The contact wires are not perfectly aligned in two rows; instead, the termination ends  27  of contact wires  20 - 1  and  20 - 5  are located approximately 0.020 inches below the termination ends  27 ,  28  of the other contact wires in the top row, and the termination ends  27  of contact wires  20 - 4  and  20 - 8  are located approximately 0.020 inches above the termination ends  27 ,  28  of the other contact wires in the bottom row. The termination end  27  of each contact wire is spaced apart horizontally from its adjacent contact wire(s) by 0.040 inches. In some embodiments of the present invention, the vertical stagger on pairs  1  and  3  may be sufficiently pronounced so as to flip the polarity of the coupling between pairs  1  and  3  between the plug contact regions  22  and the crossover section  24  of the contact wires on pairs  1  and  3  (i.e., in the plug contact region  22 , the largest coupling is between contact wires  20 - 3  and  20 - 4  and between 20-5 and 20-6, whereas the vertical stagger is sufficiently large such that even before the crossover in pair  3 , the coupling flips polarity and is between contact wires  20 - 4  and  20 - 6  and between contact wires  20 - 3  and  20 - 5 ). This vertical stagger may be used to start compensating for the offending crosstalk introduced in the plug and in the plug contact region  22  of the contact wires  20  even before the crossover in pair  3 . 
     The vertically-oriented wiring board  40  may be formed of conventional materials and may comprise, for example, a printed circuit board. The wiring board  40  may be a single layer board or may have multiple layers. The wiring board  40  may be substantially planar as illustrated, or may be non-planar. As discussed above, each of the contact wires  20  is mounted to the vertically-oriented wiring board  40 . This may be accomplished, for example, by inserting the press-fit terminations into a respective metal-plated aperture  41 - 48  in the wiring board  40  for current carrying members of the lead frame, as shown in  FIG. 2 . Metal-plated apertures  43 ′ and  46 ′ are also provided which receive the non-current carrying members of the second termination ends of contact wires  20 - 3  and  20 - 6 . A plurality of conductive traces  49  (see  FIG. 7 ) are provided on the wiring board  40 . The conductive traces  49  may be formed of conventional conductive materials and may be deposited on the wiring board  40  via any deposition method known to those skilled in this art to be suitable for the application of conductors. A current carrying one of the conductive traces  49  connects to a respective one of the metal-plated apertures  41 - 48  to provide conductive paths from each of the metal plated apertures  41 - 48  to a respective output terminal  60  (see  FIGS. 2 and 7 ) of the communication jack  10 . Conductive traces  49  are also connected to metal-plated apertures  43 ′ and  46 ′ to provide a conductive path to compensation elements within wiring board  40 . 
       FIG. 7  is a plan view of one implementation of the vertically-oriented wiring board  40  according to certain embodiments of the present invention. The wiring board  40  is a multi-layer wiring board, and hence in  FIG. 7 , the conductive traces  49  are given different cross-hatching schemes which indicate the particular layer of the wiring board  40  on which each conductive trace  49  resides. Electrical connections are made between conductive traces on different layers of the wiring board  40  using one or more metal-plated vias  59  (or other layer-transferring structures known to those skilled in this art). As shown in  FIG. 7 , each of the metal plated apertures  41 - 48  that receive the fixed portion  25  (in the form of an eye-of-the needle termination) of a respective one of the contact wires  20  is electrically connected to a respective one of the IDC apertures  51 - 58  via a respective conductive path. Each conductive path is formed by one or more of the conductive traces  49  and conductive vias  59 . In this manner, each of the contact wires  20 - 1  through  20 - 8  is electrically connected to a corresponding one of the output terminals  60 . As is also shown in  FIG. 7 , various crosstalk compensation structures  50  may be included on the wiring board  40 . In particular, a first capacitor  61  is provided on the wiring board  40  that is connected, via apertures  41  and  43 ′ and conductive traces, to the second termination end  28  of contact wire  20 - 3  and to contact wire  20 - 1  to provide additional crosstalk compensation between pairs  2  and  3 . A second capacitor  62  is provided on the wiring board  40  that is connected, via apertures  48  and  46 ′ and conductive traces, to the second termination end  28  of contact wire  20 - 6  and to contact wire  20 - 8  to provide additional crosstalk compensation between pairs  3  and  4 . Placing capacitors on the ring side can also be done for general differential-to-differential crosstalk compensation between pairs  2  and  3  and/or between pairs  3  and  4 . In further embodiments of the present invention, the second termination end  28  of the contact wire  20 - 3  and the termination end of contact wire  20 - 5  may be connected, via apertures  43 ′ and  45  and conductive traces, to an additional capacitor, and/or the second termination end  28  of the contact wire  20 - 6  and the termination end of contact wire  20 - 4  may be connected, via apertures  44  and  46 ′ and conductive traces, to an additional capacitor, in order to provide additional differential-to-differential crosstalk compensation between pairs  1  and  3 . Such additional differential-to-differential crosstalk compensation may be provided, for example, on vertically-oriented wiring board  40  in embodiments that do not include the horizontally-oriented wiring board  70 . 
     Referring once again to  FIG. 2 , eight output terminals  60  project rearwardly from the wiring board  40  to connect electrically with respective conductors (e.g., the conductors of a twisted pair cable). In this particular embodiments, the output terminals  60  are in the form of eight insulation displacement contacts (“IDCs”)  60 . An IDC  60  is inserted into a respective one of eight metal plated IDC apertures  51 - 58  that are provided on the vertically-oriented wiring board  40 . The IDCs are of conventional construction and need not be described in detail herein; exemplary IDCs are illustrated and described in U.S. Pat. No. 5,975,919 to Arnett. 
     As best shown in  FIGS. 2 and 3 , the communications jack  10  may also include a second, horizontally-oriented wiring board  70  that is supported within the jack housing  11 .  FIG. 8  is a plan view of one implementation of the horizontally-oriented wiring board  70  according to certain embodiments of the present invention. As shown in  FIG. 2 , the horizontally-oriented wiring board  70  is positioned above the free ends  23  of the contact wires  20  and beneath the top cover  19 . The wiring board  70  has eight contact pads  71 - 78  arrayed adjacent to a front edge thereof, wherein the pads  71 - 78  are operatively aligned with corresponding ones of the free ends  23  of the contact wires  20 . Capacitance elements  63  for providing capacitive crosstalk compensation are provided on or within layers of the wiring board  70  which are connected to corresponding pairs of the contact pads  71 - 78 . While the embodiment of  FIGS. 2-8  described herein includes the horizontally-oriented wiring board  70 , it will be appreciated that, in other embodiments of the present invention, this second horizontally-oriented wiring board  70  may be omitted, and the crosstalk compensation that is provided on the second horizontally-oriented wiring board  70  may instead be provided elsewhere such as, for example, on the vertically-oriented wiring board  40 . 
     When a mating plug is received within the plug aperture  18  of jack frame  11  along the direction of plug axis P, contacts of the plug engage the free ends  23  of the contact wires  20  and urge the free ends  23  upward where they mate with a corresponding one of the contact pads  71 - 78  on the wiring board  70  (note that while in this particular embodiment contact pads are provided on all of the contact wires  20 , in other embodiments, contact pads may only be provided for some of the contact wires  20 ). Capacitive compensation is introduced in wiring board  70  via capacitors  63  that are connected to the contact pads  71 - 78  on wiring board  70  via conductive traces  49 . This capacitive compensation will have a polarity that is generally opposite to the polarity of the crosstalk that is introduced in the mating plug and in the plug contact region of the contacts  20 . Note that a first capacitor  63  is provided that connects via respective ones of the contact pads to the free ends  23  of contact wires  20 - 3  and  20 - 5 , and that a second capacitor  63  is provided that connects via respective ones of the contact pads to the free ends  23  of contact wires  20 - 4  and  20 - 6 , for the purpose of providing pair  1  to pair  3  differential-to-differential crosstalk compensation. Additional capacitors  63  are provided on horizontally-oriented wiring board  70  to provide capacitive compensation between various other pair combinations. It will also be understood that additional capacitive compensation is introduced on the vertically-oriented wiring board  40 . This additional capacitive compensation on wiring board  40  (see  FIG. 7 ) may comprise capacitive compensation elements  61 ,  62 ,  63  that have the same polarity as the compensation introduced on the horizontally-oriented wiring board  70  (which is a polarity that is opposite the polarity of the crosstalk introduced in the plug and/or in the plug contact region of the contact wires  20 ) and/or additional stages of compensation that have generally the opposite polarity as the compensation introduced on the horizontally-oriented wiring board  70  (and hence a polarity that is generally the same as the polarity of the crosstalk introduced in the plug and in the plug contact region of the contact wires  20 ). In such two-stage crosstalk compensation schemes the crosstalk compensation that is a polarity that is opposite the polarity of the crosstalk introduced in the plug and/or in the plug contact region of the contact wires  20  is generally referred to as “first stage compensation”, and the crosstalk compensation that has a polarity that is generally same as the polarity of the crosstalk introduced in the plug and in the plug contact region of the contact wires  20  is referred to as “second stage compensation.” First stage compensation introduced on the horizontally-oriented wiring board  70  may be shared with additional first stage compensation in wiring board  40 , or wiring board  40  may only contain the second stage compensation, depending on the utilization of wiring board  70 . According to one embodiment, when the first stage compensation is located close to apertures  41 - 48 , the second stage compensation will be positioned closer to the IDCs  60 . Methods of using such two-stage compensation schemes to reduce crosstalk levels in a communications jack are described in detail in U.S. Pat. No. 5,997,358 to Adriaenssens et al. 
     The communications jacks  10  according to embodiments of the present invention may provide excellent differential-to-differential and differential-to-common mode crosstalk compensation. With respect to differential-to-differential crosstalk, typically the greatest amount of such crosstalk is generated in the mating plug and in the plug contact region  22  of the contact wires  20  between the pair  1  and the pair  3  signal paths. To compensate for this differential-to-differential crosstalk between pairs  1  and  3 , it is desirable to obtain significant levels of both inductive and capacitive crosstalk compensation among the pair  1  and the pair  3  contact wires in the lead frame. As shown best in  FIGS. 3 and 5 , because of the crossover in the contact wires  20 - 3 ,  20 - 6  of pair  3 , contact wires  20 - 3  and  20 - 5  are positioned so that the termination ends  27  thereof are in close proximity to each other, and hence will generate compensating inductive crosstalk. This coupling may be designed to compensate for the offending crosstalk that is generated between contact wires  20 - 3  and  20 - 4  in the plug contact regions thereof and for crosstalk introduced between the blades in positions  3  and  4  of the mating plug. Likewise, contact wires  20 - 4  and  20 - 6  are positioned so that the termination ends  27  thereof are in close proximity to each other, and hence will generate compensating inductive crosstalk. This coupling may be designed to compensate for the offending crosstalk that is generated between contact wires  20 - 5  and  20 - 6  in the plug contact regions thereof and for crosstalk introduced between the blades in positions  5  and  6  of the mating plug. 
     As discussed above, capacitive crosstalk compensation is also provided to compensate for the differential-to-differential crosstalk between pairs  1  and  3 . This capacitive crosstalk compensation is introduced at essentially zero delay (which is the equivalent of introducing the capacitive compensation at the plug/jack mating point in the lead frame) by providing capacitive elements  63  on the horizontally-oriented wiring board  70  that are electrically connected to contact wires  20 - 3  and  20 - 5  (a first capacitor) and contact wires  20 - 4  and  20 - 6  (a second capacitor) when a mating plug is received within the plug aperture  18  in a manner similar to that shown in U.S. Pat. No. 6,350,158 to Arnett et al. The combination of the above-described capacitive crosstalk compensation mechanisms allows the communications jack  10  to provide excellent differential-to-differential crosstalk compensation on the most problematic differential pairs (i.e., pairs  1  and  3 ). Additionally, by virtue of the large stagger in current carrying tip members of pairs  1 ,  3 ,  2  and  4 , (contacts  20 - 5 ,  20 - 3 , excluding second termination end,  20 - 1 , and  20 - 7 ), being positioned in a row above current carrying ring members of pairs  1 ,  3 ,  2  and  4 , (contacts  20 - 4 ,  20 - 6 , excluding second termination end,  20 - 2 , and  20 - 6 ), differential-to-differential inductive crosstalk compensation is achieved. In some embodiments, this differential-to-differential inductive crosstalk compensation along with capacitive differential-to-differential compensation within vertically-oriented wiring board  40  may provide sufficient pair  1  to pair  3  differential-to-differential crosstalk compensation. As noted above, in such embodiments, the horizontally-oriented wiring board  70  may be omitted. 
     The communications jack  10  also provides differential-to-differential crosstalk compensation for various other pair combinations. As can be seen in  FIGS. 3 and 5 , the second termination end  28  of contact wire  20 - 3 , which is non-current carrying, is positioned closer to the termination end  27  of contact wire  20 - 1  than it is to the termination end  27  of contact wire  20 - 2 , which provides capacitive differential-to-differential compensation for crosstalk generated between contact wires  20 - 2  and  20 - 3  in the plug contact region  22  where contacts wires  20 - 2  and  20 - 3  are closely aligned in a side-by-side relationship. Similarly, the second termination end  28  of contact wire  20 - 6 , which is non-current carrying, is positioned closer to the termination end  27  of contact wire  20 - 8  than it is to the termination end  27  of contact wire  20 - 7 , which provides capacitive compensation for crosstalk generated between contact wires  20 - 6  and  20 - 7  in the plug contact region  22  where contacts wires  20 - 6  and  20 - 7  are closely aligned in a side-by-side relationship. Note that when coupled members are carrying current they couple both capacitively and inductively, and when they do not carry current they can only couple capacitively. 
     Additionally, as discussed above, capacitive compensation elements may also be provided on the vertically-oriented wiring board  40 . In particular, as shown in  FIG. 7 , a first capacitive element  61  may be provided on the wiring board  40  that is connected to the second termination end  28  of contact wire  20 - 3  and to contact wire  20 - 1  to provide additional crosstalk compensation between pairs  2  and  3  on the tip side. To adjust for balance, as needed, capacitive elements can be connected on the ring side between the second termination end  28  of contact wire  20 - 6  and contact wire  20 - 2  (not included in  FIG. 7 ). As current does not flow through the second termination end  28  of contact wires  20 - 3  and  20 - 6 , this capacitive crosstalk compensation is advantageously introduced at a low delay. Similarly, a second capacitive element  62  may be provided on the wiring board  40  that is connected to the second termination end  28  of contact wire  20 - 6  and to contact wire  20 - 8  to provide additional crosstalk compensation between pairs  3  and  4  on the ring side. As current does not flow through the second termination end  28  of contact wire  20 - 6 , this capacitive crosstalk compensation is also introduced at essentially zero delay. Similar compensation (not included in  FIG. 7 ) can be introduced on the tip side contacts as needed for balance. As shown in  FIG. 7 , various other crosstalk compensation structures  63 , including both capacitive and inductive structures and first and second stage compensation structures, may be provided on the wiring board  40 . Capacitive compensation structures  63  are also provided on wiring board  70 . Inductive compensation on wiring board  70  cannot be accomplished in this particular embodiment since current carrying paths are not provided on wiring board  70 . 
     In addition to providing differential-to-differential crosstalk compensation, the communications jack  10  can also provide excellent differential-to-common mode crosstalk compensation. Due to the large physical separation between both pair  2  and pair  4  and one of the conductors of pair  3 , the highest levels of differential-to-common mode crosstalk, which can be the most problematic to channel performance, tend to occur on pairs  2  and  4  when pair  3  is excited differentially. The differential-to-common mode crosstalk occurring when any of the pairs  1 ,  2  and  4  is excited differentially tends to be much less severe, and consequently much less problematic, because the separation between the contact wires in each of these pairs is one-third the separation between the contact wires of pair  3 . Because of the crossover in the contact wires  20 - 3  and  20 - 6  of pair  3 , the communications jack  10  can provide inductive crosstalk compensation for the differential-to-common mode crosstalk that occurs on pairs  2  and  4  when pair  3  is differentially excited. Because the most problematic differential-to-common mode crosstalk can be inductively compensated, a communications jack employing this arrangement can meet higher performance standards, particularly at elevated frequencies. By virtue of the relatively large stagger and crossovers in pairs  3 ,  2  and  4 , inductive differential-to-differential crosstalk compensation between pairs  3  and  2  and between pairs  3  and  4  is also attained simultaneously. The large stagger between pair  3  and pair  1  also introduces compensation to minimize the historically problematic differential-to-differential crosstalk that occurs with this pair combination. 
     EXAMPLE 1 
     Calculations have been performed to estimate the differential-to-differential and differential-to-common mode crosstalk values that can be achieved using the communications jack of  FIGS. 2-8 . Table 1 below lists the differential-to-differential and differential-to-common mode crosstalk values that are generated in the “in-line” portion of the contact wires  20  that includes the plug contact region of each contact. Note that the in-line geometry and the resulting crosstalk is also common to that occurring in typical communication plugs. The values are provided in terms of mV/V/inch, and hence the total crosstalk values may be computed by multiplying the values in Table 1 by the length of the in-line portion of the contacts. Crosstalk between pairs  2  and  4  were not calculated as these levels are typically quite low due to the large physical separation between the contact wires of pairs  2  and  4 . In Table 1, “XL” represents the inductive crosstalk between the identified pairs, “XC” represents the capacitive crosstalk between the identified pairs and “Total” represents the sum of XL and XC. All tabulated inductive responses (XL) were derived using calculations that assumed magnetic coupling between line filaments, and tabulated capacitive responses (XC) used calculations based on capacitive coupling between circular wires having circumference equivalent to actual 10×17 mil cross-sections. (Equation references are in Walker, Capacitance, Inductance, and Crosstalk Analysis, Sections 2.2.8 and 2.3.8). The latter calculations are approximate because shielding effects are not taken into consideration. Further, differential-to-common mode responses assume a common mode impedance of 75 ohms, a value whose absolute value need not be exact for this purpose. Tables 2 and 3 below use the same conventions as Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 In-Line Section Crosstalk 
               
            
           
           
               
               
               
            
               
                   
                 Differential-to- 
                 Differential-to- 
               
               
                   
                 Differential 
                 Common Mode 
               
               
                 Differential 
                 NEXT 
                 NEXT 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Pairs 
                 XL 
                 XC 
                 Total 
                 XL 
                 XC 
                 Total 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 to 2 
                 1.85 
                 0.55 
                 2.40 
                 −5.38 
                 −0.88 
                 −6.26 
               
               
                 1 to 3 
                 −21.65 
                 −3.76 
                 −25.01 
                 0 
                 0 
                 0 
               
               
                 1 to 4 
                 1.85 
                 0.55 
                 2.40 
                 5.38 
                 0.88 
                 6.26 
               
               
                 2 to 1 
                 1.85 
                 0.55 
                 2.40 
                 −5.38 
                 −0.88 
                 −6.26 
               
               
                 2 to 3 
                 −7.38 
                 −1.27 
                 −8.65 
                 −7.13 
                 −1.87 
                 −9.00 
               
               
                 3 to 1 
                 −21.65 
                 −3.76 
                 −25.01 
                 0 
                 0 
                 0 
               
               
                 3 to 2 
                 −7.38 
                 −1.27 
                 −8.65 
                 17.78 
                 3.51 
                 21.29 
               
               
                 3 to 4 
                 −7.38 
                 −1.27 
                 −8.65 
                 −17.78 
                 −3.51 
                 −21.29 
               
               
                 4 to 1 
                 1.85 
                 0.55 
                 2.40 
                 5.38 
                 0.88 
                 6.26 
               
               
                 4 to 3 
                 −7.38 
                 −1.27 
                 −8.65 
                 7.13 
                 1.87 
                 9.00 
               
               
                   
               
            
           
         
       
     
     As shown in Table 1, the differential-to-common mode crosstalk levels for pair  3  to pair  2  and for pair  3  to pair  4  are comparatively large (a magnitude of 21.29 mV/V/inch), indicating a large unbalance for these pair combinations. The differential-to-common mode crosstalk levels for pair  1  to pair  2  and for pair  2  to pair  1 , pair  1  to pair  4  and pair  4  to pair  1  are also unbalanced, but to a lesser extent. The large differential-to-differential crosstalk between pair  1  and pair  3  (magnitude of 25.01) is also evident. Such large levels of both types of crosstalk resulting from the in-line geometry is also common to typical communication plugs and, historically, has been the significant source of unwanted crosstalk. 
     Table 2 provides the differential-to-differential and differential-to-common mode crosstalk values calculated using this approach that are provided in the back part of the lead frame (i.e., between the contact terminations and the crossover region). As shown in Table 2, the differential-to-differential crosstalk between pair  1  and pair  3 , between pair  2  and pair  3 , and between pair  3  and pair  4  each have polarities that are opposite to the polarities of the crosstalk between those pair combinations that is generated in the in-line portion of the contacts, as can be seen from Table 1. As such, Table 2 shows that the lead frame provides differential-to-differential crosstalk compensation for each of these pair combinations. While the crosstalk between pair  1  and to pair  2  and between pair  1  to pair  4  have the same polarity as that in Table 1, the overall levels are small and not problematic. Also as shown in Table 2, the differential-to-common mode crosstalk on pair  2  to pair  1 , pair  2  to pair  3 , pair  3  to pair  2 , pair  3  to pair  4 , pair  4  to pair  1  and pair  4  to pair  3  have the opposite polarity as is shown in Table 1, and hence provide compensating crosstalk. As the pair  3  to  2  and pair  3  to  4  differential-to-common mode crosstalk is kept at relatively low levels, improved alien crosstalk performance may be obtained as compared to prior art jacks. While the pair  1  to pair  2  and pair  1  to pair  4  values have the same polarity as shown in Table 1, and hence are non-compensating, the overall levels on these pair combinations are manageable. Hence, Table 2 illustrates how the communications connectors according to embodiments of the present invention can be designed to provide improved differential-to-differential and differential-to-common mode crosstalk compensation. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Crosstalk in remainder of Lead Frame 
               
            
           
           
               
               
               
            
               
                   
                 Differential-to- 
                 Differential-to- 
               
               
                   
                 Differential 
                 Common Mode 
               
               
                 Differential 
                 NEXT 
                 NEXT 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Pairs 
                 XL 
                 XC 
                 Total 
                 XL 
                 XC 
                 Total 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 to 2 
                 5.87 
                 0.71 
                 6.58 
                 −3.85 
                 −0.51 
                 −4.36 
               
               
                 1 to 3 
                 32.79 
                 3.21 
                 36.00 
                 0 
                 0 
                 0 
               
               
                 1 to 4 
                 5.87 
                 0.71 
                 6.58 
                 3.85 
                 0.51 
                 4.36 
               
               
                 2 to 1 
                 5.87 
                 0.71 
                 6.58 
                 4.06 
                 0.55 
                 4.61 
               
               
                 2 to 3 
                 10.31 
                 2.13 
                 12.44 
                 0.52 
                 1.81 
                 2.33 
               
               
                 3 to 1 
                 32.79 
                 3.31 
                 36.00 
                 0 
                 0 
                 0 
               
               
                 3 to 2 
                 10.31 
                 2.13 
                 12.44 
                 −11.41 
                 −1.70 
                 −9.71 
               
               
                 3 to 4 
                 10.31 
                 2.13 
                 12.44 
                 11.41 
                 1.70 
                 9.71 
               
               
                 4 to 1 
                 5.87 
                 0.71 
                 6.58 
                 −4.06 
                 −0.55 
                 −4.61 
               
               
                 4 to 3 
                 10.31 
                 2.13 
                 12.44 
                 −0.52 
                 −1.81 
                 −2.33 
               
               
                   
               
            
           
         
       
     
     In another embodiment of the present invention, the contact wire arrangement of  FIG. 3  is modified by positioning the termination end  27  of contact wire  20 - 4  of pair  1  10 mils closer (in the horizontal or “x” direction of  FIG. 5 ) to the termination end  27  of contact wire  20 - 1  of pair  2  and positioning termination end  27  of contact wire  20 - 5  of pair  1  10 mils closer (in the horizontal or “x” direction of  FIG. 5 ) to the termination end  27  of contact wire  20 - 8  of pair  4 . This modified contact wire arrangement leads to slightly improved balance between pairs  1  and  2  and between pairs  1  and  4  (and hence improved differential-to-common mode crosstalk on pair  2  and pair  4  when pair  1  is excited differentially). It is, however, at the small expense of the pair  1  to pair  3  differential-to-differential (hence pair  3  to pair 1 ) crosstalk compensation. (28.37 vs. 36.0). Table 3 below provides the differential-to-differential and differential-to-common mode crosstalk values calculated using this modified lead frame. Crosstalk between pairs  2  and  4  were not calculated as these levels are typically quite low due to the large physical separation between the contact wires of pairs  2  and  4 . 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Crosstalk in Remainder of Modified Lead Frame 
               
            
           
           
               
               
               
            
               
                   
                 Differential-to- 
                 Differential-to- 
               
               
                   
                 Differential 
                 Common Mode 
               
               
                 Differential 
                 NEXT 
                 NEXT 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Pairs 
                 XL 
                 XC 
                 Total 
                 XL 
                 XC 
                 Total 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 1 to 2 
                 6.28 
                 0.78 
                 7.06 
                 −1.74 
                 −0.20 
                 −1.94 
               
               
                 1 to 3 
                 25.50 
                 2.88 
                 28.37 
                 0 
                 0 
                 0 
               
               
                 1 to 4 
                 6.28 
                 0.78 
                 7.06 
                 1.74 
                 0.20 
                 1.94 
               
               
                 2 to 1 
                 6.28 
                 0.78 
                 7.06 
                 4.51 
                 0.63 
                 5.14 
               
               
                 2 to 3 
                 10.31 
                 2.13 
                 12.44 
                 0.52 
                 1.81 
                 2.33 
               
               
                 3 to 1 
                 25.50 
                 2.88 
                 28.37 
                 0 
                 0 
                 0 
               
               
                 3 to 2 
                 10.31 
                 2.13 
                 12.44 
                 −11.41 
                 −1.70 
                 −9.71 
               
               
                 3 to 4 
                 10.31 
                 2.13 
                 12.44 
                 11.41 
                 1.70 
                 9.71 
               
               
                 4 to 1 
                 6.28 
                 0.78 
                 7.06 
                 −4.51 
                 −0.63 
                 −5.14 
               
               
                 4 to 3 
                 10.31 
                 2.13 
                 12.44 
                 −0.52 
                 −1.81 
                 −2.33 
               
               
                   
               
            
           
         
       
     
     Numerous additional modifications may be made to the communications jack of  FIGS. 2-8  without departing from the scope of the present invention. As one example, although eight contact wires are provided in the communications jack  10 , other numbers of contact wires may be employed. For example, 16 contact wires may be employed, and one or more crossovers that cross over a pair of contact wires that are sandwiched therebetween may be included in those contact wires. Likewise, other configurations of jack frames, covers and IDC housings may be used in further embodiments of the present invention. As another example, the contact wires may have a different profile and/or the contact wires may be mounted in a different pattern on the vertically-oriented wiring board. Similarly, the IDCs may be mounted in a different pattern on the wiring board and/or some other type of connection terminals may be used in place of IDCs. In some embodiments, the crossovers on pairs  2  and  4  may be omitted and/or may be placed on the vertically-oriented wiring board instead of in the contact wires. Additionally, interdigitated finger capacitors or other capacitive elements could be used on the vertically-oriented and/or horizontally-oriented wiring boards instead of the plate capacitors that are primarily used in the embodiments of  FIGS. 2-8 . 
     As a further example, the communications jacks may be employed within a patch panel or series of patch panels as opposed to comprising a stand-alone communications jack. Likewise, the second termination ends of the contact wires of pair  3  may be located in different positions on the wiring board than those shown in the exemplary embodiment depicted above. The vertical stagger on pair  3  may also be further or less exaggerated and, in some embodiments, the contact wires of pair  1  may have a larger vertical stagger than the contact wires of pair  3 . 
     In the claims appended hereto, as well as in the summary section above, it will be understood that the terms “first”, “second”, “third” and the like, when used in reference to a contact wire, conductor, differential pair or the like, are not necessarily being used to refer to a specific contact wire, conductor or differential pair as specified in, for example, the TIA/EIA 568, type B configuration, but instead are used merely to distinguish one contact wire, conductor or differential pair from other contact wires, conductors or differential pairs that are recited in the claim. Thus, for example, a “first contact wire” that is referenced in the claims may refer to any contact wire in the TIA/EIA 568, type B configuration, or may refer to a contact wire according to some other configuration. 
     It will also be appreciated that changes may be made to the contact wire configurations shown herein. By way of example,  FIG. 9  is an enlarged perspective view of the contact wires of a communications jack according to further embodiments of the present invention that includes a slightly modified contact wire arrangement. This contact wire arrangement could be used, for example, in the jack of  FIG. 2  with appropriate modifications to the compensation circuitry on the wiring boards  40 ,  70 . 
     As shown in  FIG. 9 , eight contact wires  120 - 1  through  120 - 8  are provided, each of which may comprise a conductive element that is used to make physical and electrical contact with a respective contact on a mating communications plug. Contact wires  120 - 1 ,  120 - 2 ,  120 - 3 ,  120 - 6 ,  120 - 7  and  120 - 8  may be identical to contact wires  20 - 1 ,  20 - 2 ,  20 - 3 ,  20 - 6 ,  20 - 7 , and  20 - 8 , respectively, of  FIGS. 2-4 , and hence will not be discussed further herein. 
     Contact wires  120 - 4  and  120 - 5  may also be almost identical to contact wires  20 - 4  and  20 - 5 , respectively, of  FIGS. 2-4 . The difference between contact wires  120 - 4  and  20 - 4  is that the base portion of contact wire  120 - 4  includes a 10 mil horizontal jog  121  towards contact wire  120 - 1  (a jog in the negative y-direction in  FIG. 9 ), whereas contact wire  20 - 4  does not include any jog in the y-direction. The difference between contact wires  120 - 5  and  20 - 5  is that the base portion of contact wire  120 - 5  includes a 10 mil horizontal jog  122  towards contact wire  120 - 8  (a jog in the y-direction in  FIG. 9 ), whereas contact wire  20 - 5  does not include any jog in the positive y-direction. It will be appreciated that the extent of the horizontal jogs  121 ,  122  may be varied from 10 mils. The 10 mil jogs are somewhat exaggerated in  FIG. 9  so that they can be more readily seen. 
     As discussed above with respect to  FIG. 5 , the contact wires of pairs  1  and  3  may include vertical staggers that are sufficiently large so as to flip the polarity of the coupling between the contact wires of pairs  1  and  3  between the plug contact regions  22  and the crossover section  24  of the contact wires on pairs  1  and  3  so as to start compensating for the offending crosstalk introduced in the plug and in the plug contact region  22  of the contact wires  20  even before the crossover  24  in the contact wires of pair  3 . In particular, the portions of contact wires  120 - 3  and  120 - 5  behind the plug contact region  22  (i.e., the portions between the plug contact regions  22  and the wiring board) bend upwardly, while the portions of contact wires  120 - 4  and  120 - 6  behind the plug contact region  22  bend downwardly. Thus, while contact wire  120 - 3  couples more heavily with contact wire  120 - 4  than it does with contact wire  120 - 5  in the plug contact region  22 , behind the plug contact region  22  (i.e., towards the base of the contacts), the polarity of the coupling reverses so that contact wire  120 - 3  couples more heavily with contact wire  120 - 5  than it does with contact wire  120 - 4 , even before the crossover  24  in contact wires  120 - 3  and  120 - 6  is reached. Similarly, contact wire  120 - 6  couples more heavily with contact wire  120 - 5  than it does with contact wire  120 - 4  in the plug contact region  22 , but behind the plug contact region  22 , the polarity of the coupling reverses so that contact wire  120 - 6  couples more heavily with contact wire  120 - 4  than it does with contact wire  120 - 5 , even before the crossover  24  in contact wires  120 - 3  and  120 - 6  is reached. The inclusion of the horizontal jogs  121 ,  122  may allow increased amounts of compensating crosstalk to be introduced between pairs  1  and  3  in the contact wires, as the horizontal jog  121  in contact wire  120 - 4  brings the base portion of contact wire  120 - 4  closer to contact wire  120 - 6  and as the horizontal jog  122  in contact wire  120 - 5  brings the base portion of contact wire  120 - 5  closer to contact wire  120 - 3 . Moreover, in some embodiments, the horizontal jogs  121 ,  122  may be located between the plug contact region  22  and the crossover  24  so as to further facilitate reversing the polarity of the coupling prior to the crossover  24 . It will also be appreciated that the polarity of the coupling need not be reversed prior to the crossover  24 . For instance, in some embodiments the vertical stagger and/or horizontal jogs  121 ,  122  may not be sufficient to reverse the polarity, but may still reduce the total amount of offending crosstalk that is generated between pairs  1  and  3 , thus reducing the amount of crosstalk that must be compensated for later in the communications jack. 
     In the embodiment pictured in  FIG. 9 , the 10 mil horizontal jog  121  moves the base portion of contact wire  120 - 4  in the negative y-direction, while the 10 mil horizontal jog  122  moves the base portion of contact wire  120 - 5  in the positive y-direction. As discussed above, this can provide enhanced differential-to-differential crosstalk compensation between pairs  1  and  3 . Pursuant to further embodiments of the present invention (not pictured in  FIG. 9 ), the directions of these jogs may be reversed such that the base portion of contact wire  120 - 4  includes a 10 mil horizontal jog in the positive y-direction (towards contact wire  120 - 8 ) and the base portion of contact wire  120 - 5  includes a 10 mil horizontal jog in the negative y-direction (towards contact wire  120 - 1 ). These jogs may facilitate improving differential-to-common mode crosstalk between pair  1  and the two outside pairs (pairs  2  and  4 ). 
     The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.