Fire resistant cable for use in local area network
First Claim
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1. A fire retardant telecommunications cable for use within a building, which has a low structural return loss, comprising:
- a core consisting of a plurality of insulated conductors in groups of twisted pairs wherein the number of twisted pairs in said core is at least five;
each of said conductors having a single, relatively uniform, insulation layer of a non-fire retardant polyolefin composition;
each of said groups of conductors being twisted to have a different lay with respect to each other as a group and the twisted pairs of the groups having two or more different lay lengths; and
an outer jacket of flame retardant material surrounding said core;
said cable having a structural return loss (SRL) in a frequency range of 20-100 MHz determined by a formula SRLf ≧
SRL200 -10 log10 (f/20) where f is the frequency and SRL200 is the SRL at 20 MHz and SRL200 is at least 23 dB.
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Abstract
A fire retardant cable for use primarily as a riser cable in buildings has a plurality of groups of twisted pairs of conductors arranged in a "honeycomb" structure. Each conductor comprises a metallic conducting member encased in a single layer of a non-flame retardant polyolefin material such as high density polyethylene. The groups of conductors are surrounded by a jacket of flame retardant poly(vinyl chloride) material.
78 Citations
12 Claims
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1. A fire retardant telecommunications cable for use within a building, which has a low structural return loss, comprising:
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a core consisting of a plurality of insulated conductors in groups of twisted pairs wherein the number of twisted pairs in said core is at least five; each of said conductors having a single, relatively uniform, insulation layer of a non-fire retardant polyolefin composition; each of said groups of conductors being twisted to have a different lay with respect to each other as a group and the twisted pairs of the groups having two or more different lay lengths; and an outer jacket of flame retardant material surrounding said core; said cable having a structural return loss (SRL) in a frequency range of 20-100 MHz determined by a formula SRLf ≧
SRL200 -10 log10 (f/20) where f is the frequency and SRL200 is the SRL at 20 MHz and SRL200 is at least 23 dB. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A fire retardant telecommunications cable for use as a riser cable, which has a low structural return loss, comprising:
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a core including a plurality of insulated conductors in groups of twisted pairs, wherein the number of twisted pairs in said core is at least five; each of said conductors having a single, relatively uniform, insulation layer of non-fire retardant polyolefin composition; each of said groups of conductors twisted to have a different lay with respect to each other as a group, and the twisted pairs of the groups having two or more different lay lengths; and an outer jacket of flame retardant material surrounding said core; wherein said cable has a fire retardant capability sufficient for use as a riser cable and has a structural return loss margin ranging from approximately 7.8 dB to approximately 13.5 dB in a frequency range of 20-100 MHz.
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12. A fire retardant telecommunications cable for use within a building, which has a low structural return loss, comprising;
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a core including a plurality of insulated conductors in groups of twisted pairs; each of said conductors having a single, relatively uniform, insulation layer of a non-fire retardant polyolefin composition; each of said groups of conductors being twisted to have a different lay with respect to each other as a group and the twisted pairs of the groups having two or more different lay lengths; and an outer jacket having a composition constituted of approximately fifty percent (50%) GP-4 PVC resin;
approximately five and two-tenths percent (5.2%) stabilizers including approximately three and one-half percent (3.5%) tribasic lead sulfate;
approximately one and one-half percent (1.5%) lubricants including Henkel G-16 and Henkel G-71;
approximately twenty-two percent (22%) plasticizers including up to five percent (5%) 711 phthalate, approximately twelve percent (12%) tetra-brominated di-2-ethyl-hexyl phthalate, and approximately five percent (5%) mixed phosphate ester; and
approximately twenty-one percent (21%) flame retardants including alumina trihydrate and antimony trioxide.
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Specification