WO1999045611A1

WO1999045611A1 - Improved manner of electrical connection

Info

Publication number: WO1999045611A1
Application number: PCT/AU1999/000139
Authority: WO
Inventors: George Georgevits
Original assignee: Power And Digital Instruments Pty. Ltd.
Priority date: 1998-03-06
Filing date: 1999-03-05
Publication date: 1999-09-10
Also published as: AUPP224298A0

Abstract

An electrical connector (71) with two jack frames (72, 73) to provide electrical connection between two RJ45 type plugs (74, 75). Each jack frame (72, 73) has a rear portion from which extends eight conducting elements (92) allocated as four pairs, running side by side in an array. The array has at least one of the pairs of conducting elements (92) crossed over each other to exchange positions once near the rear portion of one jack frame and once again near the rear portion of the other jack frame. Crosstalk between the circuits of the pairs of conducting elements (92) induced in the plugs and jack frames is almost exactly cancelled by crosstalk signal induced between the circuits of said pairs of conducting elements (92) between the crossovers. Matching RJ45 plugs are described which, together with the connector (71), provide further improved performance.

Description

IMPROVED MANNER OF ELECTRICAL CONNECTION

BACKGROUND AND SUMMARY OF THE INVENTION

This invention concerns electrical connectors and more specifically connectors ideally suited for but not limited to use in communications, especially communications between computer equipment, particularly computers connected in a local area network.

In the past decade there have been huge demands placed on communications systems to handle ever faster data exchange between computers. Hardware that was more than satisfactory for voice communication, operating at transmission frequencies of up to 1MHz, has been found to be unsatisfactory for computer communications operating at frequencies of up to 5 MHz. More recently Australian Standard AS/NZS 3080:1996 specified a standard for wiring systems, including connectors, which were required to operate at up to 100MHz. This level of performance has become known in the communications industry as Cat 5. Recently EIA in the United States of America has developed a draft standard defining a category known as "Enhanced Cat 5" or Cat 5E and the International Standards Organisation (ISO) released a new draft standard which requires network performance to beyond 200MHz which has become known as Cat 6, and to 600MHz which has become known as Cat 7.

At each increased level of performance it becomes more difficult to meet the required transmission specifications by way of modifications to existing hardware designs. In addition, there is a substantial capital investment in existing voice and data network equipment using RJ45 type connectors. It is highly desirable to have a communication system which uses RJ45 type connectors and not only meets the Cat 6 requirements, but whose components are also backwardly compatible with existing hardware such that Cat 6 plugs when engaged with Cat 5 sockets, or Cat 5 plugs when engaged with Cat 6 sockets, would still achieve Cat 5 performance for the coupled pair. Considerable effort has been expended by many organisations in attempting to develop new types of electrical jacks and plugs which can mate with existing well known standard RJ45 plugs and jacks respectively to provide Cat 5 performance, but which are also capable of levels of performance above Cat 5 when the new types of connectors are used together. There is a need for a cost-effective way to achieve this goal and this need is addressed by the present invention.

In one aspect the present invention provides an electrical plug adapted to mate with an RJ45 type jack, the plug providing electrical connection for eight conductors arranged in four twisted pairs in a cable and having:

- its body made from dielectric material, with

- a nose end adapted to lead the plug when being inserted into the jack,

- a tail end, opposite the nose end, adapted to accommodate a four twisted pair cable, - a contact face having eight electrical contacts adapted to make electrical contact with corresponding conductors in the jack,

- a locking face, opposite the contact face, having a resilient catch which locks the plug into the jack,

- the eight insulated wires in the four twisted pairs extending at least substantially the full length of the plug from the nose to the tail,

- each pair maintaining its twist for at least 50% of the plug length,

- terminal pins which pass, from the contact face near the nose end, into the plug and make firm electrical contact with the respective individual wires, and

- the heads of the pins exposed on the contact face to form the electrical contacts.

Preferably:

- the pin heads are elongated in the direction of insertion of the plug,

- each pair of wires maintains its twist for at least 60% of the plug length, and more preferably for at least 70% of the plug length, - the top of each pin head is vertically rounded in the direction of insertion of the plug,

- the wires are held in wire guides corresponding to the allocated terminal positions, 3

- the wire guides are eight bores 8 to 12mm deep formed in the dielectric body, each wire being a loose clearance fit in its respective bore,

- the axis of each bore is aligned in the end to end direction of the plug,

- the firm electrical contact made by each terminal pin with its respective wire is by way of the pin penetrating the wire and more preferably passing through the wire,

- the wire has a stranded copper core,

- the nose end of the plug includes an insert which includes the eight bores and which is held to the body of the plug by the terminal pins, and/or

- within the plug there is no sharp bend in any of the wires.

In another aspect the present invention provides a method of assembling onto a cable an electrical plug adapted to fit an RJ45 type jack, the method including:

1. selecting a plug having a body moulded from a dielectric material said plug body having: a) a nose end adapted to slide into the jack, b) a tail end opposite the nose end, c) a locking face having a resilient latch which in use locks the plug into the jack, d) a contact face, opposite the locking face, having electrical contacts adapted to make electrical contact, with the conductors in the jack, and e) eight guides for wires,

2. selecting a four twisted pair cable and releasing its eight wires from the cable's sheath for at least 10mm at an end of the cable,

3. allocating wires to respective terminal positions on the plug, 4. placing the wires in respective wire guides corresponding to the allocated terminal positions, and 5. for each wire, driving a pin through a guide hole from the contact face to make firm contact with the wire in its respective wire guide in order to provide electrical contact from the wire to a head on the pin at the contact face.

Preferably: 4

1. the eight wires are released from the cable's sheath for between 15mm and 25mm at an end of the cable,

2. the wire guides are bores from 8mm to 12mm long and wires are pushed through the holes until they protrude from the nose end and are later cut off flush with the nose end,

3. the wire guides are contained in an insert adapted to fit into the nose of the plug,

4. each wire is a clearance fit in its bore so that the bore fully supports the wire when the pin is driven to make contact with the wire,

5. each pin is driven through its respective wire and into a blind recess formed in the wall of the bore opposite the guide hole, and/or

6. the step of driving the pins through the wires also includes driving a cable clamping wedge against the cable sheath and its enclosed wires near the tail end of the plug and locking the wedge into its cable clamping position, thus providing strain relief for the wires terminated within the plug.

In a further aspect the present invention provides an electrical connector, adapted to provide electrical connection between two RJ45 type plugs, the connector having two jack frames, each jack framecomprising:

1. an opening at its front through which one of the plugs would be inserted to engage said plug in a cavity,

2. within the cavity a contact face having eight electrical contacts adapted to make electrical contact with corresponding terminals on the plug engaged therein,

3. a locking face, opposite the contact face, having a catch which cooperates with a latch on the mating plug to lock the plug into the jack frame, 4. a rear portion from which extends eight conducting elements, running side by side in an array, and electrically linking the eight electrical contacts in the jack frame to corresponding eight electrical contacts in the other jack frame, the array having: a) a first pair of conducting elements being the two central conducting elements in the array, b) a second pair of conducting elements comprising the combination of the conducting elements immediately to each side of the first pair, 5

c) a third pair of conducting elements being the two conducting elements at a first end of the array, and d) a fourth pair of conducting elements being the two conducting elements at the second end of the array, e) at least one of said pairs of conducting elements crossed over each other to exchange positions once near the rear portion of one jack frame and once again near the rear portion of the other jack frame, whereby crosstalk between the circuits of said pairs of conducting elements induced in the plugs and jack frames is almost exactly cancelled by crosstalk signal induced between the circuits of said pairs of conducting elements between the crossovers.

Preferably the crosstalk signal induced between the circuits of said pairs of conducting elements is induced mostly by distributed mutual inductance and distributed capacitance effects between said pairs of conducting elements.

More preferably crosstalk signal induced between the circuits of said pairs of conducting elements is induced by distributed mutual inductance and capacitance effects without significant assistance from lumped capacitances or inductances.

Preferably the second pair of conducting elements cross to exchange positions in the array near the rear portion of one jack frame and cross to exchange positions once again near the rear portion of the other jack frame, and the conducting elements of the first, third and fourth pairs run from one jack frame to the other jack frame without crossing each other.

Alternatively:

- said first pair of conducting elements cross over each other once near the rear portion of one jack frame and once again near the rear portion of the other jack frame, - the conducting elements of the second pair run from one jack frame to the other jack frame without crossing each other, 6

- the third pair of conducting elements cross over each other once near the rear portion of one jack frame and once again near the rear portion of the other jack frame, and

- the fourth pair of conducting elements cross over each other once near the rear portion of one jack frame and once again near the rear portion of the other jack frame.

The connector so described may be mated with an RJ45 type plug in each jack frame, said plugs each being connected to a respective cable having four twisted pairs of conductors, wherein the length of the portion of each conducting element in said first, third or fourth pair between the two places in the array where it crosses over its paired conducting element is approximately half the length of the electrical path measured between where the pair is twisted closest to the connector in one plug and where the pair is twisted closest to the connector in the other plug.

The connector may be adapted for mounting on a wall or panel where one jack frame is open at the front of the wall or panel whereby a user may plug in a fly lead for communication equipment and the other jack frame is within or at the rear of the wall or panel whereby usually fixed cabling for premises distribution is attached in order to link the connector with the rest of a communications network.

The invention also provides in a further aspect the combination of a connector as above described when mated with an RJ45 type plug in each jack, said plugs each being connected to respective cables having four twisted pairs of conductors, where the crosstalk induced into said first, third or fourth pairs between the crossover points of each pair almost exactly cancels the crosstalk induced in each pair respectively elsewhere in the electrical path between where the pair is twisted closest to the connector in one said plug and where the pair is twisted closest to the connector in the other said plug.

In another aspect the present invention provides a method of providing fixed cabling for a communications network in a premises using four twisted pair cable including:

1. installing fixed cabling in the premises with RJ45 type plugs on each end of the fixed cables, 7

2. providing an end of each fixed cable to a respective outlet where a service point is required,

3. installing faceplates at the outlets, each faceplate housing one or more electrical connectors as described above having two jack frames,

4. providing access to one of said jack frames at the front of each installed faceplate for users of the network to connect a fly lead to that front jack frame,

5. providing access to the other said jack frame from only the rear of the faceplate, and

6. connecting to said other, rear, jack frame at each faceplate the RJ45 type plug on the fixed cable designated for the outlet.

In another aspect the present invention provides a communications cabling system for a premises having:

1. fixed cabling in the premises with RJ45 type plugs on each end of the fixed cables,

2. an end of each fixed cable provided to a respective outlet where a service point is required,

3. a faceplate at each outlet, each faceplate housing one or more electrical connectors as described above having two jack frames,

4. one of said jack frames accessible at the front of each installed faceplate for users of the network to connect a fly lead, 5. the other said jack frame accessible from the rear of the faceplate, and

6. the fixed cable designated for the outlet having its plug mated with the rear jack frame.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example, different elements of the present invention will now be described with reference to the attached drawings, none of which are to scale, where:

Figure 1 is a simplified schematic sketch of a plan view of the underside of a plug in accordance with one aspect of the present invention before its connection to a cable,

Figure 2 is a cutaway side view of the plug shown in Figure 1, 8

Figure 3 is an end view of the plug shown in Figure 1,

Figure 4 is an isometric view of an insert which becomes portion of the plug shown in Figure 1,

Figure 5 shows three views, labelled A, B and C, of a terminal pin used in the plug in Figure 1 ,

Figure 6 is a simplified schematic sketch of the plug shown in Figure 1 after its connection to an electrical cable,

Figure 7 is a cutaway side view of the plug and cable shown in Figure 6,

Figure 8 is a see-through elevation view showing an electrical connector, in accordance with the invention, for connecting together two plugs of the form shown in Figures 1, 2, 6 and 7,

Figure 9 is a front elevation view of a jack having an alternative shaping of the plug-receiving opening to that shown in other Figures,

Figure 10 is a discontinuous cutaway side view of the connector shown in Figure 8,

Figure 11 is a discontinuous cutaway plan view of the connector shown in Figure

8,

Figure 12 is a diagram illustrating the layout of conductors in the connector shown in Figure 8, Figures 13 to 15 illustrate alternative configurations of connectors having similar characteristics to that shown in Figure 10,

Figure 16 is an exploded view showing an alternative, particularly preferred, form of a connector in accordance with the invention,

Figure 17 is a view of one component in the connector shown in Figure 16. Figures 18 to 22 are diagrams illustrating the principles by which the present invention achieves crosstalk reduction,

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Figures 1 to 7, electrical plug 1 is adapted to mate with an RJ45 type jack. Its body 2 is moulded from dielectric plastics material chosen by conventional materials selection procedures to provide the appropriate degree of electrical insulation, low 9

dielectric loss at high frequencies and other dielectric properties for the purpose. The plug has a nose end 4 adapted to be offered up to and slid into the jack, a tail end 6 opposite the nose end, a contact face 8, a locking face 10 and two side faces 11.

The locking face 10 is opposite the contact face 8 and has a resilient catch lever or latch 12 which locks the plug into the jack. The contact face has a step 46 separating the main plane 44 from the stepped plane 48. The step provides for a housing 26 for a moveable portion which, when locked into place, provides strain relief for the wires in the plug. Eight shallow channels 29 are let into the main plane 44 from the nose end 4 and these serve to guide and locate the corresponding resilient terminals when mating the plug 1 with an RJ45 jack. The walls 30 between the channels 29 extend to the same level as the main plane 44. The dimensions of the main plane 44, step 46, stepped plane 48 and channels 29 are the same as those for conventional RJ45 plugs. Set within the channels 29 are eight terminal pins 19 and 20 adapted to make electrical contact with corresponding conductors in the mating jack.

The tail end 6 is adapted to accommodate a four twisted pair cable 14 of conventional construction preferably to Cat5 or, more preferably, Cat6 specification, having an outer sheath 15 and four twisted pairs of stranded copper wires 16. The plug 1 provides electrical connection for these eight wire conductors. The present invention is particularly suited to cable constructed with stranded wire.

When wiring up the plug 1 to the cable 14, the sheath is removed from approximately 50mm of the end of the cable to release the four twisted pairs of wires, which are then untwisted back to the point where they leave the sheath. The eight wires are then inserted into eight bores 27 and 28 formed in a nose insert 13, which is then slid with the inserted wires through the tail end 6 of the plug body 2 and pulled through as far as possible. When slid into position in the body 2, the bores extend to the nose end 4 with the axis of each bore 27 and 28 aligned in the end to end direction of the plug. The bores 27 and 28 form guides for the wires which are pushed through until they protrude slightly from the nose end 4 of the contact half-shell 18. Each wire 16 is a loose clearance fit in its bore 27 and 28, each of which is approximately 10mm long and 10

corresponds to a respective terminal pin 19 and 20. The allocation of wires to terminals is usually according to one of a variety of standard allocations in wide use internationally, the most common of which is detailed in Australian Standard AS/NZS 3080:1996, known as T568A, and is illustrated in Figure 12 of this patent specification.

The portions of wire protruding from the nose 4 are tensioned slightly, to pull the twists in the wire pairs hard up against the bores inside the plug, and terminal pins 19 and 20 are driven along respective guide holes 17 and 18, to penetrate through wires 16 and protrude into recesses 24 formed in the wall of the bore opposite the respective guide hole. As each wire is a loose clearance fit in its bore, the bore wall fully supports the wire when the pin is driven into the wire, so preventing any possibility of the pin not passing through the stranded copper core of the wire and ensuring good electrical contact. Each pin has a barb on its point and this helps prevent the pin from working its way out of the insulation covering the wire.

At the same time as the pins 19 and 20 are driven into their respective wires, the cable 14 is being clamped at the tail end of the connector. Referring to Figures 2 and 7, before the clamping operation a wedging member 51 sits within a wedge access hole 52 attached to the body 2 of the plug by an integrally moulded hinge 54. During the pin driving stage of plug assembly, the wedging member 51 is pressed from within the access hole and into the cable. The wedging member pivots on its hinge 54 until its latching tip 56 clicks past the edge 57 which prevents its return. The wedging member has a generally triangular cross section.

The short lengths of wire left protruding from the nose 4 are then cut off flush. As an alternative, a recess could be provided around each bore where it exits the nose end in order that the wires could be trimmed off shorter than flush with the nose end; but in each situation the eight wires in the four twisted pairs extend at least substantially the full length of the plug from the nose to the tail.

As seen from Figure 3, the bores 28 are offset away from the contact face 8 relative to the row of bores 27. Figure 2 shows how the long pins 20 are offset away from the nose 11

end 4 relative to the row of short pins 19. Both these offsets serve to greatly reduce the crosstalk between a circuit carried by the offset conductors and other circuits when the plug is used in a communications network using the T568A or similar termination designations. This reduction in crosstalk is due to a reduction in both inductive and capacitive contributions to the crosstalk.

It is desirable that the twisting of each pair is maintained right up until the last possible point where they must separate to enter their respective bores 27 and 28 and the unwinding of each pair should be performed in the context of the amount to which the other pairs have been unwound. As a guide, each pair should maintain its twist for at least 70% of the plug length; by way of comparison, for conventional RJ45 plugs it is usual practice to provide guides for the wires which ensure no crossing occurs at all in the 50% of the plug length closest to the nose end.

All the terminal pins 19 and 20 are identical, except that two different lengths are used. Short pins 19 are used for terminals 31, 32, 34, 35, 37 and 38 while long pins 20 are used for terminals 33 and 36. Figure 3 shows a short pin 19 ready to press home in order for its head to form terminal 31 and a long pin 20 ready to press home for its head to form terminal 33. Figure 2 shows these two pins when looking at the side face 11 of the plug and the heads protrude beyond the top of the channel walls 30. As shown in Figure 3, other short pins have already been pressed home to form terminals 32, 34 and 35 while a long pin has been pressed home to form terminal 36. For illustrative purposes the pins for terminals 37 and 38 have been deleted in Figure 3.

Referring to Figure 5, each pin 19 and 20 is made from gold plated brass and has a shank 21 having an ovoid cross section with a major diameter of about 1.0mm and a minor diameter of about 0.4mm, and a head 22 laterally elongated in the same direction as the major diameter of the shank 21. Pins 19 and 20 also have a barbed point 23 which interacts with the wire penetrated and keeps the pins in position. This is in the context of each wire being about 1.0mm diameter including its insulative coating and having a stranded copper core of about 0.65mm diameter. The head 22 is gently rounded in the direction of elongation as shown in view A but has flat axial walls in the 12

foreshortened direction as shown in view B. This allows the head 22 of each pin to penetrate into the channels 29 and bear on the floor of the channel when driven home. The diameter of the bores 27 and 28 is about 1.Omm, and these have a minimum wall thickness of about 1.0mm, so the short pins are driven about 2.5mm from their position shown for terminal 31 in Figures 2 and 3 to that shown for terminal 34. Before the short pins 19 are driven home the heads protrude beyond the top of the channel walls 30. As the long pins need to be driven further, about 3.5mm, so they protrude somewhat more from the channel walls before being driven home.

When the plug is assembled and connected to a cable as described above, the heads of the pins exposed in the channels on the contact face form the electrical terminals for connection to the mating jack. By this means it is determined exactly where in the channel the contact is made, so removing one source of variation between plugs.

The terminals 31 to 38 formed by the pin heads 19 and 20 in the channels are in two rows, with terminals 31, 32, 34, 35, 37 and 38 in the row close to the nose end 4 while terminals 33 and 36 are in the row offset back a little further from the nose end. This offset of terminals 33 and 36 along with the pin shape serve to reduce the capacitive effects between the pins in the different communication circuits. It is important that each pair of terminals corresponding to a twisted pair of wires is in the same one of these rows. The offset is about the same distance as that between adjacent pins in the row close to the nose end. Accordingly the distance of the pin for terminal 33 from the pin for terminal 32 is about 1.4 times the distance of the pin for terminal 31 from the pin for terminal 32. However the reduction of the capacitive effect due to offsetting the pins is due to more than the effect of distancing the pins from each other. Because the pin shanks and heads have an elongated cross section, a component of the reduction is due to the offsetting of the pins relative to each other.

With respect to Figures 8 to 12, an electrical connector 71 is illustrated which provides electrical connection between two RJ45 type plugs 74 and 75. It should be noted that these Figures are drawn not to scale but instead are drawn for ease of explanation. The 13

connector 71 has a connector body 77 having two RJ45 type jack frames 72 and 73 mounted back to back and connected together by an array of conducting elements 92.

Each jack frame 72, 73 has an opening 78 at its front through which one of the plugs 74, 75 would be inserted to locate in a cavity 80. One face of the cavity is a contact face 82 having eight elongated electrical contacts 84 which, when a plug is mated, make electrical contact with corresponding terminal pins 19 and 20 on the plug. The opposite face 86 of the cavity is a locking face having a catch which cooperates with a latch on the mating plug to lock the plug into the jack.

From their points of exit 97 at the rear 90 of jack frame 72 the array 92 of eight conducting elements 101 to 108 run side by side to corresponding exit points 98 at the rear of jack frame 73 to electrically link the eight electrical contacts 84 of jack frame 72 to the corresponding eight electrical contacts 84 of jack frame 73.

The array is designed to have best performance when the RJ45 connectors are terminated according to the T568A Standard. This is illustrated in Figure 12 and the particular terminal allocation will be well known to those skilled in the wiring of modern communications circuits using RJ45 connectors. Of the four twisted pairs, pair #1 is allocated to terminals T4 and T5 (being the central two conducting elements in the array) while pair #2 is allocated to terminals T3 and T6 (being respectively the terminals immediately to each side of the first pair). Pair #3 uses terminals Tl and T2 while pair #4 uses terminals T7 and T8.

The cutaway view in Figure 11 has been chosen to illustrate the manner of application of the layout shown in Figure 12 to the array 92 of conducting elements in this embodiment of the invention. The conducting elements of pairs #1, #3 and #4 are crossed over their corresponding pair partner once (at 121, 122 and 123 respectively) near the rear portion 90 of jack frame 72 and once again (at 124, 125 and 126 respectively) near the rear portion 91 of the other jack frame 73. The conducting elements of array 92 may not be covered in any electrically insulative material so the crossovers 121 to 126 are achieved by a saddle bend formed in the conducting elements 14

at the relevant positions. The spacings between the conductive elements 92 are maintained the same as for a standard RJ45 plug throughout the connector.

The connector described is about 40mm in length, 20mm high and 25mm wide as seen in Figure 8. The electrical contacts 84 on the contact face 82 commence about 5mm inside the jack frame cavity 80 and extend about 7mm further in to the back of the cavity. The rear 90, 91 of the cavities are about 12mm apart so giving a total conductor length of about 30mm between the locating tips 94.

Each conducting element 101 to 108 and its corresponding elongated contacts 84 in both jack frames 72 and 73 is formed from a contiguous piece of thin metallic strip and all of these may be assembled from two lead frames using known lead frame technology. The conducting elements are located within the body 77 of the connector by assembling the body from two moulded halves (not illustrated). The tip 94 of each contact portion 84 is bent and pressed using an interference fit into a hole in the contact face 82 of the jack frame cavity 80.

The connector shown in Figures 8 and 10 has conducting elements 101 to 108 extending in a substantially flat array directly between the backs of the jack frames. In order to keep the length of the connector to a minimum, while still providing sufficient length of conducting elements between crossovers 121 to 123 and corresponding crossovers 124 to 126, it may be desirable to take the conducting elements by a less direct route such as that shown in Figure 13. This would involve bending the array along a line transverse to the length of the individual conducting elements. The array 292 of conducting elements run from their exit points 297 in jack frame 272 via crossovers 221, 222 and 223 following the same general line as the elongated electrical contacts in the jack for a greater distance than for the connector of Figure 10 before bending up to join, via crossovers 224, 225 and 226 to exit points 298 in jack 273.

The path length of conducting elements required between the crossovers is determined by the amount of crosstalk compensation required to counter the effect of conductors running parallel to each other from the end of the cable sheath to the crossover. 15

In order to shorten the length of conducting elements required between the crossovers, it is preferred to place the crossovers as close as practicable to the back of the jack frames.

The connector described in relation to Figures 8 to 12 has jack frame 72 inverted relative to jack frame 73. This means the contact faces 82 of the frames 72 and 73 face in opposite directions (up and down respectively as illustrated) relative to each other. In this way the positions of the circuit pairs are the same for each jack and there is no reversal of the polarity of any individual pair. An alternative arrangement, as shown in Figure 14, would be for the jack frames to not be inverted relative to each other. This however would have the possibly undesirable consequence of reversing the position of pair #3 with pair #4, and reversing the polarity of each pair, and would require another connection through a similar connector elsewhere in the circuit in order to preserve standard wiring pinouts. This may not be a practical problem if the fixed wiring in a premises was terminated at each end with such connectors because the required double reversal would take place, once at the connector at each end of a wiring run.

Another variant on the connector described in relation to Figures 8 to 12 would be for the two jack frames to be mounted at right angles as shown in Figure 15. This would permit a shorter version of the connector better suited to location in thin wall panels and with better accessibility in some circumstances. The configuration of the array of conducting elements in such a connector would again be of the same general form as that shown in Figure 12 except that, like the embodiments of Figures 13 and 14, the array is partially folded differently. The array 492 of conducting elements runs from their exit points 497 in jack frame 472 via crossovers 421, 422 and 423 following the same general line as the elongated electrical contacts in the jack for a greater distance than for the connectors of Figure 10 or 13 before bending up in two 45 degree bends to join, via crossovers 424, 425 and 426 to exit points 498 in jack 473. The right angled connector shown in Figure 15 has the same disadvantage as the connector of Figure 14 in that the position of pairs #3 and #4 would be reversed. However it can be readily seen how jack frame 472 in Figure 15 could be inverted and moved down in order to provide no such reversal while still preserving the same path for the array 492. 16

Although physically disimilar, the connectors of Figures 10, 13, 14 and 15 share an array of conducting elements which is the same in design except for the positioning of folds. It is preferred that no folds greater than 45 degrees are placed into the array.

Instead of folds, curves can be formed into the array in order to produce the required change of direction. This can be achieved conveniently by using a flexible printed circuit board instead of a bent lead frame as described above. A flexible PCB can even be twisted through a 180° helix in order to provide a more desired orientation relationship between the two jack frames.

An example of the use of a rigid printed circuit board will now be described with reference to Figures 16 and 17. Figure 16 shows an exploded view of half of a back-to- back connector 127. In a schematic sense the connector is similar to the connector shown in Figure 14; each end of the connector 127 is identical so only one end is shown in Figure 16 in order to aid clarity. Some components which are present as multiple copies in the connector, are not replicated in Figure 16, and such instances will be readily apparent to a person skilled in the art.

The connector 127 comprises electrical conductor and insulator components encased in a two-part case which clips together. The case has a base 128 which has a flat central portion 132, which serves as a floor for the case, and a jack frame housing 130 at two opposite ends. Each of the two housings 130 has an RJ45-type jack frame 131 opening away from the base 128. The case has a cover 134 which clips onto the base 128 such that the front wall 136 of the cover aligns generally with the shoulder 138 on the floor.

A printed circuit board (PCB) 140 rests upon the inside floor 132 of the case. Each end of the PCB is narrowed to form a tab 142 and these neatly locate into the rear of the jack frame housings 130. The tab 142 has formed therethrough eight holes in two rows each of four holes. The printed circuit board 140 is of double sided conductor construction and the pattern of conducting pathways is described later in this specification. The array of four holes 160 toward the edge of the printed circuit board is laterally offset relative 17

to the array of four holes 162 further inwards from the edge. The offset provides the necessary minimum pin to pin clearance on the PCB so as to meet the relevant pin to pin voltage breakdown requirements.

Affixed to the tab 142 is a pin mounting bracket 164 made of dielectric material which has four out-set (or front) holes 168 and four in-set (or rear) holes 170 which, when the bracket 164 is mated to the printed circuit board in its operating position, are coaxial with the holes 160 and 162 in the tab 142.

The rear of the pin mounting bracket 164 has an upstanding wall with eight slots therein. These slots form a comb 166 into which contact pins are located. The contact pins extend from the arrays of holes 160 and 162 to the corresponding slot in the bracket. The four pins 172 inserted in the front holes 168 have a slightly different shape to the pins 174 inserted in the rear holes 170. The purpose of the shape difference is to accommodate the different distances from the comb 166 to the holes 168 and 170 while still providing a uniform length for the longest straight portion on all the pins as required to meet RJ-45 specifications.

The printed circuit board 140 carries conducting tracks on both its faces. The path of these is shown in Figure 17. The tracks which would be hidden from view are indicated by dashed lines. Tracks 151 to 154 are on the top face of the board, while tracks 155 to 158 are on the underneath face.

Connectors manufactured as described above using a conductor array on a PCB have been found to provide well in excess of Cat 5E performance when mated with a standard RJ45 plug.

With the exception of tracks 152 and 157, the tracks cross over their respective paired conductor in the region just outwards of the shoulder 144. The length of the tracks are sized such that the distance between the two crossovers of one conductor with its paired conductor is as near as possible to half the distance of the conductive path length 18

measured from the point where the pair is twisted closest to the connector in one jack to the point where the pair is twisted closest to the other connector in the other jack.

In order to explain how the present invention acts to improve the operation of electrical connectors, the principle of crosstalk reduction in balanced circuits will now be explained with reference to Figures 18 to 22.

When two balanced circuits having generally parallel conductors are placed in close proximity to each other, some crosstalk will be induced. This is illustrated in Figure 18 where a signal is produced by a signal source 180 in the upper circuit 186 having a load 179 in the diagram. The arrows indicate the induction of crosstalk from the upper circuit 186 comprising conductors 181 and 182 into the lower circuit 187 comprising conductors 183 and 184 and loads 177 and 178. The amount of crosstalk increases as the conductors are brought closer together, and as the frequency is increased.

Crosstalk induction occurs because the coupling between conductors 182 and 183 is greater than that between conductors 181 and 183, since conductor 182 is closer than conductor 181 to to conductor 183. Similarly, coupling occurs between conductors 181 and 184, and between 182 and 184, but these crosstalks are of a smaller magnitude because the separation distances are greater.

In order to minimise the effects of crosstalk, circuit designers often introduce anti-phase coupling. This is achieved by placing a crossover in one of the circuits, at the halfway point 190, as illustrated at Figure 19. Thus normal phase crosstalk is induced in the first length 188 of the second circuit up to the point of crossover, and antiphase crosstalk of equal magnitude to that induced in the first half is induced in the second half 190 of the circuit, the net effect being nil overall crosstalk induction over the full length of the circuit. The way in which the abovementioned principle of crosstalk reduction is applied in couplers according to the present invention will now be described. Crosstalk is induced between the pairs #l-#2, #2-#3, and #2-#4 in an RJ45 plug/jack mated pair because pair #2 (terminated on pins 3, 6 - refer AS/NZS 3080:1996, termination scheme T568A) is split by pair #1. Referring to Figure 20 which is a simplified circuit 19

representation for pairs #1 194 and #2 195 of a mated RJ45 plug and jack, if the pair #1 is considered as the first circuit and the pair #2 as the second circuit, then the arrangement shown in Figure 20 represents the circuit placements.

To nullify the effect of this crosstalk, either one of the pairs may be crossed at the halfway point, or the circuit extended to twice its length, with one of the pairs crossed. This latter procedure is adopted in relation to the present invention, as it is not possible to cross the conductors inside a mated plug/jack. Hence the equivalent circuit for pairs #1 and #2 of one mated plug/jack in the present invention can be represented as shown in Figure 21.

As the connector shown in Figure 8 effectively consists of two mated RJ45 plug/jack pairs connected in series, the equivalent circuit becomes that shown in Figure 22. In experiments, this scheme has been shown to reduce crosstalk between the two circuits by more than a factor of 1000 at a frequency of 100 MHz.

In the connector shown in Figure 8, pairs #3 and #4 each lie adjacent to one conductor of pair #2. Accordingly, if there was no crossing of the conductors of pairs #3 and #4, this arrangement would experience crosstalk characteristics similar to those of the circuits shown in Figure 18 Therefore a scheme of crossovers similar to that for pair #1 is also applied to pair #3 and pair #4.

Every effort has been made to keep the transmission characteristics of the invention as similar as possible to the actual four twisted pair cable. To this end, the conductors are made to dimensions and spacing which matches the 100 ohm characteristic impedance of the cable, thus keeping reflections to an absolute minimum, and maximising performance at high frequencies.

The invention envisages incorporating a connector as described in relation to Figures 8 to 15 and 21 into a wall plate or other outlet housing for the purpose of constructing a communications wiring system having excellent performance in comparison with presently available for RJ type connectors. All the lengths of cable used in such a 20

wiring system would be terminated with plugs as described with reference to Figures 1 to 7. The cables so used would preferably be terminated off site at a specialist cable termination operation having the relatively expensive test equipment required to check the performance of every cable as it is terminated, so ensuring the performance. While terminations would be possible after the cable is installed in position, it is considered that such a practice would be somewhat difficult and time consuming.

Such a communications wiring system as presently proposed would have many other advantages, including: • manufacturing cost of jacks and plugs similar to the presently used Cat5 and lower performance equivalents,

• transmission performance substantially superior to existing products,

• the option of a simple elegant mechanical construction using lead frame technology or a low cost printed circuit board construction inside the connector, • For a connector having a lead frame internal construction, all conductors are mainly straight and robust making manufacture easier,

• cables are pre-terminated in fixed lengths,

• substantially faster installation of cabling systems, and ability to use installers with lower skill, with consequent labour cost reduction, • substantially reducing and possibly even eliminating on-site testing,

• fixed cabling can be easily recovered from a site and reused

• cables can be relocated after installation without the need to use cabling contractors

• outlets may be relocated immediately without the need to wait for and use a cabling contractor • cables may be concatenated with much less degradation of link performance than has been possible using RJ45 type connectors to date, although in some instances with several concatenations the link performance may be degraded to below Cat6 (eg to Cat 5E or Cat 5),

• modular office furniture may be pre-cabled off-site and use joiners to connect to premises cabling 21

Where the term RJ45 type is used in this specification, it is intended to mean that the connector being described is of the general shape and form of what is generally regarded in the communications industry as an RJ45 connector. Connectors of RJ45 type include not only those illustrated in the US Standard on eight wire connectors, Figs 68.500(d)(1), 68.500(d)(2) and 68.500(d)(3), Federal Register Vol 41 Nol34 but also those with slight variations in the housing in order to accommodate proprietary mating connectors. One example of such variation is illustrated at Figure 9 where one or more offset keys are accommodated.

It is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention.

Throughout this specification, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

22CLAIMS

1. An electrical connector, adapted to provide electrical connection between two RJ45 type plugs, the connector having two jack frames, each jack frame comprising:

- an opening at its front through which one of the plugs would be inserted to engage said one plug in a cavity,

- within the cavity a contact face having eight electrical contacts adapted to make electrical contact with corresponding terminals on the plug engaged therein, - a locking face, opposite the contact face, having a catch which cooperates with a latch on the mating plug to lock the plug into the jack frame,

- a rear portion from which extends eight conducting elements, running side by side in an array, said eight conducting elements electrically linking the eight electrical contacts in said jack frame to corresponding eight electrical contacts in the other jack frame, the array having:

- a first pair of conducting elements being the two central conducting elements in the array,

- a second pair of conducting elements comprising the conducting elements immediately to each side of the first pair,

- a third pair of conducting elements being the two conducting elements at a first end of the array, and

- a fourth pair of conducting elements being the two conducting elements at the second end of the array, and - at least one of said pairs of conducting elements crossed over each other to exchange positions once near the rear portion of one jack frame and once again near the rear portion of the other jack frame, whereby crosstalk between the circuits of said pairs of conducting elements induced in the plugs and jack frames is almost exactly cancelled by crosstalk signal induced between the circuits of said pairs of conducting elements between the crossovers. 23

2. An electrical connector according to claim 1 wherein said crosstalk signal induced between the circuits of said pairs of conducting elements is induced mostly by distributed mutual inductance and distributed capacitance effects between said pairs of conducting elements.

3. An electrical connector according to claim 2 wherein said crosstalk signal induced between the circuits of said pairs of conducting elements is induced by distributed mutual inductance and capacitance effects without significant assistance from lumped capacitances or inductances.

4. An electrical connector according to any one of claims 1 to 3 wherein:

- the second pair of conducting elements cross to exchange positions in the array near the rear portion of one jack frame and cross to exchange positions once again near the rear portion of the other jack frame, and - the conducting elements of the first, third and fourth pairs run from one jack frame to the other jack frame without crossing each other.

5. An electrical connector according to any one of claims 1 to 3 wherein:

- the first pair of conducting elements cross over each other once near the rear portion of one jack frame and once again near the rear portion of the other jack frame,

- the conducting elements of the second pair run from one jack frame to the other jack frame without crossing each other,

6. A connector according to claim 4 mated with an RJ45 type plug in each of said jack frames, said plugs each being connected to a respective cable having four twisted 24

pairs of conductors, wherein the length of the portion of each conducting element in said second pair between the two places in the array where it crosses over its paired conducting element is approximately half the electrical length measured between where the second pair is twisted closest to the connector in one plug and where the second pair is twisted closest to the connector in the other plug.

7. A connector according to claim 5 mated with an RJ45 type plug in each of said jack frames, said plugs each being connected to a respective cable having four twisted pairs of conductors, wherein the length of the portion of each conducting element in said first, third and fourth pair between the two places in the array where it crosses over its paired conducting element is approximately half the length of the electrical path measured between where the pair is twisted closest to the connector in one plug and where the pair is twisted closest to the connector in the other plug.

8. A connector according to any one of claims 1 to 7 which is adapted for mounting on a wall or panel where one jack frame is open at the front of the wall or panel whereby a user may plug in a fly lead for communication equipment and the other jack frame is within or at the rear of the wall or panel whereby cabling for premises distribution is attached in order to link the connector with the rest of a communications network.

9. A connector according to any one of claims 1 to 8 wherein the two jack frames are on opposite faces of the connector with their said contact faces facing in opposite directions relative to each other and the relative positions of said electrical contacts for each of the pairs of conducting elements and the relative position of respective legs of each pair are the same for each jack.

10. A connector according to any one of claims 1 to 8 wherein the two jack frames are on opposite faces of the connector with their said contact faces both facing in the same direction and the position of the pair of electrical contacts for said third pair of conducting elements is swapped with the position of the pair of electrical contacts for said fourth pair of conducting elements. 25

11. A connector according to any one of claims 1 to 10 wherein said array of eight conducting elements is formed substantially by a lead frame.

12. A connector according to any one of claims 1 to 8 wherein said array of eight conducting elements is formed substantially by tracks on a printed circuit board.

13. A connector according to any one of claims 1 to 8 wherein said array of eight conducting elements is formed substantially by tracks on a flexible printed circuit element held in a non-planar configuration.

14. A method of providing fixed cabling for a communications network in a premises using four-twisted-pair cable including:

- installing fixed cabling in the premises with RJ45 type plugs on each end of the fixed cables,

- providing an end of each fixed cable to a respective outlet where a service point is required,

- installing faceplates at the outlets, each faceplate housing one or more electrical connectors according to any one of claims 1 to 5 having two jack frames, - providing access to one of said jack frames at the front of each installed faceplate for users of the network to connect a fly lead to that front jack frame,

- providing access to the other said jack frame from only the rear of the faceplate, and

- connecting to said other, rear, jack frame at each faceplate the RJ45 type plug on the fixed cable designated for the outlet.

15. A method of providing fixed cabling according to claim 14 wherein said RJ45 type plugs are attached to said fixed cabling prior to its arrival at said premeses.

16. A method according to claim 14 or 15 wherein the RJ45 plug on the fixed cable designated for the rear jack frame is a plug providing electrical connection for eight conductors arranged in four twisted pairs in a cable said plug having its body made from 26

dielectric material, a nose end adapted to lead the plug when being inserted into the rear jack frame, a tail end opposite the nose end said tail end adapted to accommodate a four twisted pair cable, a contact face having eight electrical contacts adapted to make electrical contact with corresponding conductors in the jack frame, a locking face opposite the contact face said locking face having a resilient catch which locks the plug into the jack frame, the eight insulated wires in the four twisted pairs extending at least substantially the full length of the plug from the nose to the tail, each pair maintaining its twist for at least 50% of the plug length, terminal pins which pass from the contact face near the nose end into the plug and make firm electrical contact with the respective individual wires, and the heads of the pins exposed on the contact face to form the electrical contacts between the plug and jack frame.

17. A communications cabling system for a premises having:

- fixed cabling in the premises with RJ45 type plugs on each end of the fixed cables,

- an end of each fixed cable provided to a respective outlet where a service point is required,

- a faceplate at each outlet, each faceplate housing one or more electrical connectors according to any one of claims 1 to 5, - one of said jack frames accessible at the front of each installed faceplate for users of the network to connect a fly lead,

- the other said jack frame accessible from the rear of the faceplate, and

- the fixed cable designated for the outlet having its plug mated with the rear jack frame.

18. An electrical plug adapted to mate with an RJ45 type jack, the plug providing electrical connection for eight conductors arranged in four twisted pairs in a cable said plug having its body made from dielectric material, a nose end adapted to lead the plug when being inserted into the jack, a tail end opposite the nose end said tail end adapted to accommodate a four twisted pair cable, a contact face having eight electrical contacts adapted to make electrical contact with corresponding conductors in the jack, a locking face opposite the contact face said locking face having a resilient catch which locks the 27

plug into the jack, the eight insulated wires in the four twisted pairs extending at least substantially the full length of the plug from the nose to the tail, each pair maintaining its twist for at least 50% of the plug length, terminal pins which pass from the contact face near the nose end into the plug and make firm electrical contact with the respective individual wires, and the heads of the pins exposed on the contact face to form the electrical contacts.

19. A plug according to claim 18 wherein the pin heads are elongated in the direction of insertion of the plug.

20. A plug according to claim 18 or 19 wherein each pair of wires maintains its twist for at least 60% of the plug length.

21. A plug according to claim 20 wherein each pair of wires maintains its twist for at least 70% of the plug length.

22. A plug according to any one of claims 18 to 21 wherein the top of each pin head is vertically rounded in the direction of insertion of the plug.

23. A plug according to any one of claims 18 to 22 wherein the wires are held in wire guides corresponding to the allocated terminal positions.

24. A plug according to any one of claims 18 to 23 wherein the wire guides are eight bores from 8 to 12mm deep formed in the dielectric body, each wire being a loose clearance fit in its respective bore.

25. A plug according to claim 24 wherein the axis of each bore is aligned in the end to end direction of the plug.

26. A plug according to any one of claims 18 to 25 wherein the firm electrical contact made by each terminal pin with its respective wire is by way of the pin passing through an insulating coating and a stranded copper core of the wire. 28

27. A plug according to any one of claims 18 to 26 wherein the nose end of the plug includes an insert which includes the eight bores.

28. A plug according to claim 27 wherein the insert is held to the body of the plug by the terminal pins.

29. A plug according to any one of claims 18 to 28 within which there is no sharp bend in any of the wires.

30. A method of assembling onto a cable an electrical plug adapted to fit an RJ45 type jack, the method including:

- selecting a plug having a body moulded from a dielectric material said plug body having: - a nose end adapted to slide into the jack,

- a tail end opposite the nose end,

- a locking face having a resilient latch which in use locks the plug into the jack,

- a contact face, opposite the locking face, having electrical contacts adapted to make electrical contact, with the conductors in the jack, and

- eight guides for wires;

- selecting a four twisted pair cable and releasing its eight wires from the cable's sheath for at least 10mm at an end of the cable,

- allocating wires to respective terminal positions on the plug, - placing the wires in respective wire guides corresponding to the allocated terminal positions, and

- for each wire, driving a pin through a guide hole from the contact face to make firm contact with the wire in its respective wire guide in order to provide electrical contact from the wire to a head on the pin at the contact face.

31. A method according to claim 30 wherein the eight wires are released from the cable's sheath for between 15mm and 25mm at an end of the cable. 29

32. A method according to claim 30 or 31 wherein the wire guides are contained in an insert adapted to fit into the nose of the plug.

33. A method according to any one of claims 30 to 32 wherein the wire guides are bores and the wires are pushed through the bores.

34. A method according to claim 33 wherein, after the pins are driven through their respective guide holes, the ends of the wires are cut off flush with said nose end.

35. A method according to claim 33 or 34 wherein each wire is a clearance fit in its bore so that the bore fully supports the wire when the pin is driven to make contact with the wire.

36. A method according to any one of claims 33 to 35 wherein the bores are from 8mm to 12mm long

37. A method according to any one of claims 33 to 36 wherein each pin is driven through its respective wire and into a blind recess formed in the wall of the bore opposite the guide hole.

38. A method according to any one of claims 33 to 37 wherein the step of driving the pins also includes driving a cable clamping wedge against the cable sheath and its enclosed wires near the tail end of the plug and locking the wedge into its cable clamping position, thus providing strain relief for the wires terminated within the plug.