GB2350229A - Flat-type communication cable - Google Patents

Abstract

A flat-type communication cable 20 for carrying frequencies in excess of 4 MHz has plural side-by-side longitudinal passageways 27,28,29,31, each having a respective twisted-pair conductor 21,22,23,24 located therein. The passageways each comprise a longitudinally extending opening 32,33,34 which opens to an adjacent passageway. The end passageways consist of a first and second end passageway having a respective first and second volume of air. First and second intermediate passageways disposed between the end passageways each have a respective third and fourth volume of air. The first volume of air is greater than the third volume of air, and the second volume of air is greater than the fourth volume of air. One of the passageways may have thicker walls than another of said passageways, a non-fluorinated polymer insulated twisted-pair conductor disposed in the passageway having thicker walls, and a fluorinated polymer insulated twisted-pair conductor disposed in the passageway having thinner walls.

Description

2350229 FLAT-TYPE COMMUNICATION CABLE The present invention relates to

unshielded communication cables and more particularly to a flat-type crescent shaped communication cable.

Various types of unshielded cables being utilized on computer systems contain 4 twisted pair conductors. The cable is restricted typically to 24 AWG conductors, a maximum of.0395" (1.0Omm) insulation, and an overall average cable OD of 0.250" (6.35mm). Further, flame test requirements also restrict the use of what type of compounds can be utilized within the cable. Because of these restrictions, twisted pair cables are often bundled together into 4 pair groups. These typically have no spacing between the individual twisted pair units. Therefore, reduction of crosstalk is limited to the selection of suitable twist lengths, where tighter twists usually exhibit enhanced crosstalk characteristics. Attenuation is limited to conductor size, typically in the range of.019' (0.48mm) to.023" (0.58mm) in diameter. A problem exists where tighter twisted pair lays degrade attenuation characteristics. Hence, a trade-off for good crosstalk is made by accepting the poorer attenuation performance of tightly twisted pairs.

It is therefore an object of this invention to provide a flat-type communication cable having a plurality of spaced twisted pair cables and which is flexible to allow relatively easy installation by installers.

According to the present invention there is provided a flat-type communication cable for carrying frequencies in excess of 4 MHz comprising:

a plurality of longitudinally extending conductor passageways positioned side-by side and including two end longitudinal conductor passageways and a plurality of side by-side intermediate conductor passageways, each of said passageways having a longitudinally extending opening which opens to an adjacent passageway, a plurality of twisted-pair conductors, a different one of said twisted- pair conductors located in each of said passageways with not more than one of said twisted pair conductors being in each of said passageways, each of said twisted- pair conductors having a cross-sectional envelope area less than a cross-sectional envelope area of the passageway in which each twisted-pair conductor is contained; at least one of said intermediate passageways has two of said longitudinally extending openings; said end passageways consist of a first end passageway and a second end passageway, said first end passageway having a first volume of air, and said second end passageway having a second volume of air; said intermediate passageways includes a first intermediate passageway having a third volume of air, and said first intermediate passageway being adjacent said first end passageway; said intermediate passageways include a second intermediate passageway having a fourth volume of air, and said second intermediate passageway being adjacent said second end passageway; said first volume of air greater than said third volume of air; and said second volume of air greater than said fourth volume of air.

Preferably, a group of four side-by-side twisted-pair conductors is formed from said plurality of twisted-pair conductors, each twisted-pair conductor from said group of four has two insulated conductors, each twisted pair from said group of four has a centre line; a distance X is a distance between the centre lines of adjacent twisted- pair conductors from said group of four twisted-pair conductors, said distance between the centre lines being when the cable is straight; each insulated conductor of each twisted-pair conductor from said group of four twisted-pair conductors has a diameter of not greater than 0.0395 inches (1.0Omm); each twisted-pair conductor of said group of four twisted-pair conductors has a twisted-pair lay length of from about 0.4 inches (10.16mm) to about 4.0 inches (101.6mm); the relative position of each twisted-pair conductor of said group of four twisted pair conductors remains within 0.9 times X when the cable has been bent in a semi circle along a longitudinal axis of the cable around a mandrel measuring 0.3 times the width of the cable; and each longitudinally extending opening forming an arc angle no greater than 70' when the cable is straight.

The cable may be unshieided, and each of said intermediate passageways may have two longitudinally extending openings.

At least one of said intermediate passageways may have two of said longitudinally extending openings; said end passageways consisting of a first end passageway and a second end passageway, said first end passageway having a first volume of air, said second end passageway having a second volume of air; said intermediate passageways including a first and a second intermediate passageway, said first intermediate passageway having a third volume of air, said first 2 intermediate passageway is adjacent to said first end passageway; said second intermediate passageway having a fourth volume of air, said second intermediate passageway adjacent to said second end passageway; said first volume of air greater than said third volume of air; said second volume of air greater than said fourth volume of air; at least one of the twisted-pair conductors is a non-fluorinated polymer insulated twisted-pair conductor; at least one of the twisted-pair conductors is a fluorinated polymer insulated twisted-pair conductor; one of said longitudinally extending passageways has thicker walls than another of said longitudinally extending passageways having thinner walls; the non-fluorinated polymer insulated twisted-pair conductor is in said passageway having the thicker walls; and the f luorinated polymer insulated twisted-pair conductor is in another passageway having the thinner walls.

There are preferably four longitudinally extending conductor passageways and four twisted-pair conductors, one twisted-pair conductor being loosely located in each of said passageways; each twisted-pair conductor has two insulated conductors defining a centre line therebetween, X being the distance between the centre line of adjacent twisted-pair conductors from said four twisted-pair conductors when the cable is straight; each insulated conductor of each twisted-pair conductor from said four twisted pair conductors has a diameter of not greater than 0.0395 inches (1.0Omm); each twisted-pair conductor of said four twisted-pair conductors has a twisted pair lay length of f rom about 0.4 inches (10.1 6mm) to about 4.0 inches (1 01.6mm); the relative position of each twisted-pair conductor of said four twisted- pair conductors remains within 0.9 times X when the cable has been bent along a longitudinal axis of the cable in a semi-circle in a semi-circle around a mandrel measuring 0.3 times the width of the cable; each longitudinally extending opening of said plurality of openings forms an arc angle no greater than 70 when the cable is straight; and one of said longitudinally extending passageways has thicker walls than another of said longitudinally extending passageways which has thinner walls.

Advantageously, each of the end passageways has a different pair of conductors disposed therein; and each of the end passageways, in which each of the respective pair of conductors is disposed, encloses at least about 30W of the cylindrical envelope of 3 each pair of conductors disposed in the end passageways.

The phrase, "multi-conductor flat-type cable" refers to cables having preferably four pairs of insulated conductors with each pair being spaced a predetermined distance apart between adjacent conductor pairs and all of the pairs being covered by an appropriate common jacket. Each of the insulated conductor pairs are loosely within the jacket and are not bonded to the jacket. Each of the insulated conductor pairs has an appropriate insulation. The insulation for all of the insulated conductor pairs may be the same. However, it is preferred that at least one of the insulated conductor pairs has a non-fluorinated polymer insulation. The insulated conductor pairs are preferably twisted pair conductors having a common insulation and the jacket is a crescent shaped solid or foam jacket with a plurality of side-by-side longitudinal passageways.

The present invention and advantages thereof will become more apparent upon consideration of the following detailed description when taken in conjunction with the accompanying drawings, in which:

The present invention and advantages thereof will become more apparent upon consideration of the following detailed description when taken in conjunction with the accompanying drawings, in which:

- Fig. 1 is a side perspective view of the flat-type cable of the present invention; Fig. 2 is a cross-section taken along lines 2-2 of Fig. 1; Fig. 3 is a partial enlarged section of Fig. 2; Fig. 4 is an enlarged cross-section of a bonded twisted pair conductor used in the present invention; and Fig. 5 is an enlarged cross-section view of another bonded twisted pair conductor used in the present invention.

The present invention provides a flat-type cable with a jacket having a plurality of twisted pair passageways -- usually four. In each passageway, there is loosely contained a twisted pair conductor. The twisted-pair conductors are spaced from each other and can have a relatively long lay length. The longer lay lengths enable the invention to utilize relatively thin wall foam insulations without crushing the cellular cavities created during the foaming process. In the present invention, three out of the possible six possible crosstalk combinations in a four pair cable are improved over the generally used cylindrical bundled four pair cable.

The flat-type cable of the present invention has a width of about 0.250 inches (6.35mm) to about 0.360 inches (9.14mm) and the twisted pair lay lengths range from about 0.4 inches (10. 1 6mm) to about 4.0 inches (1 0T.6mm). The twisted pair conductors are arranged in a generally parallel side-by-sidqconfiguration. Each insulated conductor 4 of each twisted conductor pair has a diameter of not more than 0.0395 inches (1.0Omm).

Each of the longitudinal passageways has an internal longitudinal opening extending the length of the cable jacket. The passageways restrict the movement of adjacent twisted pair conductors. The relative positions of each twisted-pair conductor remains within 0.9 times X after the flat cable has been bent in a semi-circle along the longitudinal axis around a mandrel measuring 0.3 times the width of the cable, where X is the distance between two adjacent twisted pair conductor centre lines before the cable is bent.

The cable is generally used for digital or analog communication cables having frequencies from about 1 to 500 MHz and higher and mainly above 4 MHz.

The passageways in the cable are sufficiently large such as to create pockets of airbetween the twisted-pai conductor and the wails of the passageway. Thetwisted-pair conductors are loose within each passageway, ie not bonded to the jacket.

Referring to Figs. 1 and 2 there is shown a flat crescent-shaped crosssection cable 20 of the present invention. The cable 20 shown has tour generally equivalent sized twisted pair conductors 21, 22, 23, and 24 in a side-by-side para[lel configuration, the first twisted-pair conductor 21 being on one side of the cable and the fourth twisted pair conductor 24 being on the opposite side of the cable. The cable has a single common jacket 26.

Thejacket26 is aflat-type jacket with a generally crescent shaped crosssection.

The interior of the jacket is divided into four side-by-side longitudinally extending twisted pair conductor passageways 27, 28, 29 and 31 that extend the entire length of the cable 20. Each passageway opens into an adjacent passageway by longitudinally extending openings 32, 33 and 34. Opening 32 provides an opening between adjacent longitudinal passageways 27 and 28; opening 33 provides an opening between adjacent longitudinal passageways 28 and 29; and opening 34 provides an opening between adjacent longitudinal passageways 29 and 31. The passageways may be any shape desired - ie. cylindrical, non-cylindrical, a combination of these multi-sided, etc. Figs. 1 and 2 show non-circular sectioned passageways and Fig. 3 shows circular sectioned passageways.

The twisted pairs 21, 22, 23 and 24 are loosely within the respective passageways 27, 28, 29 and 31 and are not bonded to the passageways. The end passageway 27 is sized such that when it contains twisted pair conductor 21 it has a volume of air greater than the volume of air of passageway 28 containing twisted pair conductor 22. The other end passageway 31 containing twisted pair conductor 24 is sized to have a volume of air greater than the volume of air of passageway 29 containing twisted pair conductor 23. The volume of air in passageway 27 with the twisted pair conductor 21 is preferably at least 1.2 times the volume of air of intermediate passageway 28 when it contains twisted pair conductor 22. If necessary, the volume of the end passageways 27 and 31 is increased by providing a longitudinal open pocket in the wall of the end passageways. The air pockets may be formed by using irregular shaped end passageway walls.

The term twisted pair conductor as used herein refers to two individual insulated conductors that are joined or separated and are twisted about each other. Each of the individual insulated conductors has a suitable electrical conductor surrounded by a suitable insulation. Figs. 4 and 5 as hereinafter described illustrate two types of joined insulated conductor used to form a twisted pair conductor.

It is desirable to have each of the two end passageways 27 and 31 enclose about to 95% and preferably about 87% to 93% of each of the twisted-pair cylindrical envelope 36 (Figs. 3 and 4). The two intermediate passageways 28 and 29 between the end passageways 27 and 31 enclose about 60 to 90% of the twisted pair envelope 36 and preferably 75 to 87%. The end passageways 27 and 31 preferably do not enclose less than 83% of the twisted-pair cylindrical envelope 36 and the inner or intermediate passageways 28 and 29 preferably do not enclose less than 75% of the twisted-pair cylindrical envelope 36.

Another way of considering this is to take a perpendicular cross-section through the cylindrical envelope 36 which shows a circular circumference. Thus, each of openings 32, 33 and 34 would only expose an are of about W' to about 70" and preferably between about 250 to about 470 of the circular envelope.

In another embodiment, the width or height of each opening is less than 75% of the diameter of one of the conductors of a twisted pair conductor in the passageway.

If the opening is between intermediate passageways, the opening is less than 75% of the diameter of the smallest single conductor of the twisted-pair in either of the two adjacent passageways. That is, referring to Fig. 5 for illustrative purposes, if the diameter 42A of the single conductor 42 is 0.04 inches (11.02mm), the opening will be 0.03 inches (0.76mm) or less.

Each of the longitudinal twisted-pair conductor passageways 27, 28. 29 and 31 has a cross-sectional profile area that is larger than the crosssectional profile area of the twisted-pair conductor circular envelope 36 to provide air pockets between the twisted pair conductors and their respective passageways.

Referring to Fig. 3, each of the openings 32, 33 and 34 is formed by a pair of opposite projections 37 and 38 that extend the length of.the jacket and project inwardly.

Each projection is sized to provide a stiffness that resists allowing the twisted-pair 6 conductor in one longitudinal passageway passing through to an adjacent longitudinal passageway. The configuration shown is a triangular-type cross section with a mid thickness 39 of the projections 37 and 38 generally at least 50% greater than the thickness 41 of the twisted-pair conductor insulation 42.

The separate longitudinal passageways for each twisted-pair conductor aid in increasing the spacing and keeping the twisted pair conductors separated from one another. Each twisted-pair conductor has restricted movement and tends to stay in its own space or longitudinal passageway. This restriction of movement between adjacent twisted-pair conductors reduces crosstalk susceptibility between active to passive twisted-pair conductors. Without the projection, the twisted-pair conductors would be free to move amongst one another during manufacture and/or installation which ultimately degrades the electrical characteristics of the installed cable 20.

When referring to Fig. 2, the jacket 26 for four twisted-pair conductors has a relatively continuous outer surface with central curved convex outer surface 42 and a curved concave bottom surface 43 which have respective arcs 45 and 44 separating the two inner or intermediate passageways. The jacket 26 is prepared from suitable foamed or unfoamed polymers and one of the preferred materials is a jacket material, such as polyvinyl chloride, which may be partially foamed with 10M 5% voids. The width 46 of the cable 26 is about 0.25 to 0.36 inches (6.35 to 9.14mm).

The thickness or height 47 of the cable 20 is in the range of 0.10 inches (2.54mm) to about 0.16 inches (4.06mm) and preferably between about 0.12 inches (3.05mm) to 0.14 inches (3.56mm).

The thickness of the jacket 26 not counting the projections, varies between about 0.010 inches (0.25mm) to about 0.040 inches (1.01 mm).

The thickness of the upper central portion is the largest thickness of the jacket with the centre portion 47 of the jacket convex surface 42 having the greatest thickness and the sides 48 and 49 of the jacket having the smallest thickness. The thickness of the bottom concave portion is less than the thickness of the upper convex portion and greater than the thickness of the sides 48 and 49. The ratio of the upper to the bottom thickness is in the range of between about 1.1 to 2 and preferably about 1.2.

The centre thickness 51 which does not include the length of the projections is about the same size as the diameter of a single insulated conductor and will generally be from about 0.030 inches (0.76mm) to about 0.040 inches (1.02mm). The thickness 52 of the sides 48 and 49 will be from about 0.010 inches (0.25mm) to about 0.020 inches (0.51 mm).

Thejacketand its crescent shape enhances flexibility of the cableand preserves 7 twisted pair location. This shape causes the cable to curl towards its minor axis when a bending force is applied to the cable. This effect increases the bend radius at least 2 fold when compared to cables of typical flat design since the minor axis is less than half that of comparable designs. Additionally, this curling effect takes stress off the pairs themselves, reducing the possibility of pair crossover as seen with conventional flat configuration designs.

The varying jacket thickness also provides an advantage. The curl effect gained by the crescent shape is further enhanced by increasing the jacket thickness in the centre portions of the cable 26. With the increased centre thickness, the jacket is able to hold its shape. Due to the shape of the cable, each of the passageways 27, 28, 29 and 31 have walls with varying thickness.

The radius 50 of the convex surface 42 is about 0.08 inches (2.03mm) to 1. 05 inches (26.67mm) and preferably about 0.22 inches (5.59mm). The radius 50A of the concave surface 43 is about 0.15 inches (3.81mm) to 1.1 inches (27.94mm) and preferably about 0.32 inches (8.13mm).

The twisted pair conductors have an arc 51 A passing through the centre points of the twisted pair conductors. The arc 51 A has a radius of curvature of f rom about 0.08 inches (2.03mm) to 1.05 inches (26.67mm) and preferably about 0.22 inches (5.59mm).

The inner twisted-pair conductors 22 and 23 are spaced above the side twisted pair conductors 21 and 24. That is when a transverse centre line 53 is drawn through the cross-sectional connecting points of the side twisted-pair conductors 21 and 24 and a transverse centre line 54 is drawn through the cross-sectional connecting points of the inner twisted-pair conductors 22 and 23, the distance 56 between the two centre lines within the jacket is from about 0.020 inches (0.51 mm) to about 0.060 inches (1.52mm).

The conductors 40 may be constructed of any suitable material, solid or strands, of copper, metal coated substrate, silver, nickel, aluminum, steel, alloys or a combination thereof. The dielectric may be suitable material used in the insulation of cables such as polyvinyl chloride, polyethylene, polypropylene or fluor-copolymers (such as Teflon, which is a registered trademark of Dupont), cross-linked polyethylene, rubber, etc. Many of the insulations may contain a flame retardant. The thickness of the insulation or dielectric layer 42 is in the range of from about 0.00025 inches (0. 00635mm) to about 0.0150 inches (0.381 mm).

It is preferred that at least one of the twisted-pair conductors has a non fluorinated polymer insulation. It is preferred that the passageways containing the twisted pair conductor with the non-fluorinated polymer insulation have the greatest wall thickness. The greater wall thickness acts as a flame suppressant. Therefore in the 8 embodiment shown in Figs. 1 and 2 the non-fluorinated twisted pair conductors would be either or both of twisted pair conductors 22 and 23 in passageways 28 and 29 respectively. The present construction of the cable allows the use of twisted-pair conductors having cellular insulation. Longer lay lengths can be used with the twisted pair conductors to greatly reduce the compression forces encountered with tightly twisted - i.e., short lay lengths. This allows the benefit of thin wall foam dielectrics which improve attenuation while reducing material usage. Additionally, reduction in insulation usage through foaming allows for more types of materials to be utilized while maintaining flame and electrical characteristics. Further, foaming reduces overall size of insulated singles, which is advantageous with respect to fitting ins standard industry connectors and to realizing a truly flexible construction.

Fig. 4 shows one type of joined twisted-pair conductor 60 that can be used. The twisted-pair conductor has two solid, stranded or hollow conductors 40. The conductors are solid metal, a plurality of metal strands, an appropriate fibre glass conductor, a layered metal or combination thereof. Each conductor 40 is surrounded by a respective cylindrical dielectric or insulation layer 42. Each of the conductors 40 is disposed centrally within and thus substantially concentric with the corresponding insulation 42.

The conductors 40 may, if desired, adhere to any degree against the inner walls of the respective insulation 42 by any suitable means, such as by bonding, by heat or adhesives to prevent relative rotation between the conductor 40 and insulation 42.

The insulation 42 is common for both conductors 40 as shown in Fig. 4 where the insulations 42 are integral with each other and arejoined together along their lengths in any suitable manner. As shown, the joining means is a solid integral web which extends the length of each conductor from the diametric axis of each insulation. The width 62 of the web is in the range of from about 0.00025 inches (0. 00635mm) to about 0.0150 inches (0.381 mm). The thickness 61 of the web is also in the range of from about 0.00025 inches (0.00635mm) to about 0.0150 inches (0.381mm). The web thickness is preferably less than the thickness of the dielectric layer. The web width is preferably less than the thickness of the dielectric layer.

The dual conductors surrounded by the dielectric layer are twisted to form a twisted-pair conductor. The variation in the distance between the centres of adjacent conductors, hereinafter referred to as the centre-to-centre distances, along the twisted pair cable, is very small. The centre-to-centre distance d at any one point along the twisted pair cable is predetermined.

Fig. 5 illustrates another twisted-pair conductor 65 that is joined or bonded together substantially along its entire length by an appropriate adhesive 66. Instead of 9 an adhesive, the adjacent dielectrics can be bonded together by causing material contact while the dielectrics are at elevated temperatures and then cooling to provide a joined cable having no adhesive. The non-adhesive bonding provides an integral common dielectric for the two conductors 40.

The flat-type cable of the present invention preferably has at least one non fluorinated polymer insulated twisted-pair and is especially useful as a Category 5 cable which will pass the UL91 0 flame test.

Claims (6)

1 A flat-type communication cable for carrying frequencies in excess of 4 MHz comprising:

a plurality of longitudinally extending conductor passageways positioned side-by side and including two end longitudinal conductor passageways and a plurality of side by-side intermediate conductor passageways, each of said passageways having a longitudinally extending opening which opens to an adjacent passageway, a plurality of twisted-pair conductors, a respective pair of conductors being located in each passageway, the area of the cross-sectional circular envelope containing each of the twisted-pair conductors being less than the area of the cross- sectional envelope of the conductor passageway in which the twisted-pair conductors are located; at least one of said intermediate passageways having two of said longitudinally extending openings; said end passageways consisting of a first end passageway and a second end passageway, said first end passageway having a first volume of air, and said second end passageway having a second volume of air; said intermediate passageways includes a first intermediate passageway having a third volume of air, and said first intermediate passageway being adjacent said first end passageway; said intermediate passageways include a second intermediate passageway having a fourth volume of air, and said second intermediate passageway being adjacent said second end passageway; said first volume of air greater than said third volume of air; and said second volume of air greater than said fourth volume of air.

2. The cable of claim 1, wherein a group of four side-by-sidetwisted-pair conductors isformed from said plurality& twisted-pair conductors, each twisted -pair conductor from said group of four has two insulated conductors, each twisted pair from said group of four has a centre line; a distance X is a distance between the centre lines of adjacent twistedpair conductors from said group of four twisted-pair conductors, said distance between the centre lines being when the cable is straight; each insulated conductor of each twisted-pair conductor from said group of four twisted-pair conductors has a diameter of not greater than 0.0395 inches (1.0Omm); each twisted-pair conductor of said group of four twisted-pair conductors has a 11 twisted-pair lay length of from about 0.4 inches (10.16mm) to about 4.0 inches (101.6mm); the relative position of each twisted-pair conductor of said group of four twisted-, pair conductors remains within 0.9 times X when the cable has been bent in a semi circle along a longitudinal axis of the cable around a mandrel measuring 0.3 times the width of the cable; and each longitudinally extending opening forming an arc angle no greater than 700 when the cable is straight.

3. The cable of claim 2, wherein the cable is unshielded, and each of said intermediate passageways has two longitudinally extending openings.

4. The cable of any of claims 1 to 3, wherein one of said longitu nally extending passageways has thicker walls than another of said longitudinally extending passageways which has thirwr walls; a non-fluorinated polymer insulated twisted-pair conductor is in said one of said passageways having the thicker walls, and said another of said passageways which has thinner walls containing a fluorinated polymer insulated twisted-pair conductor f rom said plurality of twisted-pair conductors.

5. The cable of claim 1, wherein at least one of said intermediate passageways having two of said longitudinally extending openings; said end passageways consisting of a first end passageway and a second end passageway, said first end passageway having a first volume of air, said second end passageway having a second volume of air; said intermediate passageways including a first and a second intermediate passageway, said first intermediate passageway having a third volume of air, said first intermediate passageway is adjacent to said first end passageway; saidsecond intermediate passageway having afourthvolume of air, said second intermediate passageway adjacent to said second end passageway; said first volume of air greater than said third volume of air; said second volume of air greater than said fourth volume of air; at least one of the twisted-pair conductors is a non-fluorinated polymer insulated twisted-pair conductor; 12 at least one of the twisted-pair conductors is a fluorinated polymer insulated twisted-pair conductor; one of said longitudinally extending passageways has thicker walls than another of said longitudinally extending passageways having thinner walls; ' ' the non-fluorinated polymer insulated twisted-pair conductor is in said passageway having the thicker walls; and the fluorinated polymer insulated twisted-pair conductor is in another passageway having the thinner walls.

6. The cable of any of claims 1 to 5, wherein there are four longitudinally extending conductor passageways and four twisted-pair conductors, one twisted-pair conductor being loosely located in each of said passageways; each twisted-pair conductor has two insulated conductors defining a centre line therebetween, X being the distance between the centre line of adjacent twisted-pair conductors from said four twisted-pair conductors when the cable is straight; each insulated conductor of each twisted-pair conductor from said four twisted pair conductors has a diameter of not greater than 0.0395 inches (1.0Omm); each twisted-pair conductor of said four twisted-pair conductors has a twisted pair lay length of from about 0.4 inches (10.1 6mm) to about 4.0 inches (1 01.6mm); the relative position of each twisted-pair conductor of said four twisted- pair conductors remains within 0.9 times X when the cable has been bent along a longitudinal axis of the cable in a semi-circle in a semi-circle around a mandrel measuring 0.3 times the width of the cable; each longitudinally extending opening of said plurality of openings forms an arc angle no greater than 700 when the cable is straight; and one of said longitudinally extending passageways has thicker walls than another of said longitudinally extending passageways which has thinner walls.

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