1755.870—RUS specification for terminating cables.
(a) Scope.
(1)
This section establishes the requirements for terminating cables used to connect incoming outside plant cables to the vertical side of the main distributing frame in a telephone central office.
(i)
The conductors are solid tinned copper, individually insulated with extruded solid dual insulating compounds.
(ii)
The insulated conductors are twisted into pairs which are then stranded or oscillated to form a cylindrical core.
(iii)
The cable structure is completed by the application of a core wrap, a shield, and a polyvinyl chloride jacket.
(2)
The number of pairs and gauge size of conductors which are used within the RUS program are provided in the following table:
| American Wire Gauge (AWG) | 22 | 24 |
|---|---|---|
| Number of Pairs | 12 | 12 |
| 50 | 50 | |
| 100 | 100 | |
| 200 | 200 | |
| 300 | 300 | |
| 400 | 400 | |
| 600 | 600 | |
| 800 | 800 | |
| Note: Cables larger in pair sizes from those shown in this table shall meet all the requirements of this section. | ||
(3)
All cables sold to RUS borrowers for projects involving RUS loan funds under this section must be accepted by RUS Technical Standards Committee “A” (Telephone). For cables manufactured to the specification of this section, all design changes to an accepted design must be submitted for acceptance. RUS will be the sole authority on what constitutes a design change.
(4)
Materials, manufacturing techniques, or cable designs not specifically addressed by this section may be allowed if accepted by RUS. Justification for acceptance of modified materials, manufacturing techniques, or cable designs shall be provided to substantiate product utility and long term stability and endurance.
(5)
The American National Standard Institute/Electronic Industries Association (ANSI/EIA) 359-A-84, EIA Standard Colors for Color Identification and Coding, referenced in this section is incorporated by reference by RUS. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of ANSI/EIA 359-A-84 are available for inspection during normal business hours at RUS, room 2845, U.S. Department of Agriculture, Washington, DC 20250-1500, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Copies are available from Global Engineering Documents, 15 Inverness Way East, Englewood, CO 80112, telephone number (303) 792-2181.
(6)
American Society for Testing and Materials Specifications (ASTM) B 33-91, Standard Specification for Tinned Soft or Annealed Copper Wire for Electrical Purposes; ASTM B 736-92a Standard Specification for Aluminum, Aluminum Alloy and Aluminum-Clad Steel Cable Shielding Stock; ASTM D 1248-84 (1989), Standard Specification for Polyethylene Plastics Molding and Extrusion Materials; ASTM D 1535-89, Standard Test Method for Specifying Color by the Munsell System; ASTM D 2287-81 (Reapproved 1988), Standard Specification for Nonrigid Vinyl Chloride Polymer and Copolymer Molding and Extrusion Compounds; ASTM D 2436-85, Standard Specification for Forced-Convection Laboratory Ovens for Electrical Insulation; ASTM D 2633-82 (Reapproved 1989), Standard Methods of Testing Thermoplastic Insulations and Jackets for Wire and Cable; ASTM D 4101-82 (1988), Standard Specification for Propylene Plastic Injection and Extrusion Materials; ASTM D 4565-90a, Standard Test Methods for Physical and Environmental Performance Properties of Insulations and Jackets for Telecommunications Wire and Cable; ASTM D 4566-90, Standard Test Methods for Electrical Performance Properties of Insulations and Jackets for Telecommunications Wire and Cable; and ASTM E 29-90, Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications, referenced in this section are incorporated by reference by RUS. These incorporations by references were approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies of the ASTM standards are available for inspection during normal business hours at RUS, room 2845, U.S. Department of Agriculture, Washington, DC 20250-1500, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Copies are available from ASTM, 1916 Race Street, Philadelphia, Pennsylvania 19103-1187, telephone number (215) 299-5585.
(7)
American National Standards Institute/National Fire Protection Association (ANSI/NFPA), NFPA 70-1993 National Electrical Code referenced in this section is incorporated by reference by RUS. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. A copy of the ANSI/NFPA standard is available for inspection during normal business hours at RUS, room 2845, U.S. Department of Agriculture, Washington, DC 20250-1500, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Copies are available from NFPA, Batterymarch Park, Quincy, Massachusetts 02269, telephone number 1 (800) 344-3555.
(8)
Underwriters Laboratories Inc. (UL) 1666, Standard Test for Flame Propagation Height of Electrical and Optical-Fiber Cables Installed Vertically in Shafts, dated January 22, 1991, referenced in this section is incorporated by reference by RUS. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. A copy of the UL standard is available for inspection during normal business hours at RUS, room 2845, U.S. Department of Agriculture, Washington, DC 20250-1500, or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Copies are available from UL Inc., 333 Pfingsten Road, Northbrook, Illinois 60062-2096, telephone number (708) 272-8800.
(b) Conductors and conductor insulation.
(1)
Each conductor shall be a solid round wire of commercially pure annealed tin coated copper. Conductors shall meet the requirements of the American Society for Testing and Materials (ASTM) B 33-91 except that requirements for Dimensions and Permissible Variations are waived.
(2)
Joints made in conductors during the manufacturing process may be brazed, using a silver alloy solder and nonacid flux, or they may be welded using either an electrical or cold welding technique. In joints made in uninsulated conductors, the two conductor ends shall be butted. Splices made in insulated conductors need not be butted but may be joined in a manner acceptable to RUS.
(3)
The tensile strength of any section of a conductor, containing a factory joint, shall not be less than 85 percent of the tensile strength of an adjacent section of the solid conductor of equal length without a joint.
(4)
Engineering Information: The sizes of wire used and their nominal diameters shall be as shown in the following table:
| AWG | Nominal diameter | |
|---|---|---|
| Millimeters | (Inches) | |
| 22 | 0.643 | (0.0253) |
| 24 | 0.511 | (0.0201) |
(5)
Each conductor shall be insulated with a primary layer of natural or white solid, insulating grade, high density polyethylene or crystalline propylene/ethylene copolymer and an outer skin of colored, solid, insulating grade, polyvinyl chloride (PVC) using one of the insulating materials listed in paragraphs (b)(5)(i) through (iii) of this section.
(i)
The polyethylene raw material selected to meet the requirements of this section shall be Type III, Class A, Category 4 or 5, Grade E9, in accordance with ASTM D 1248-84 (1989).
(ii)
The crystalline propylene/ethylene raw material selected to meet the requirements of this section shall be Class PP 200B 40003 E11 in accordance with ASTM D 4101-82 (1988).
(iii)
The PVC raw material selected to meet the requirements of this section shall be either Type PVC-64751E3XO, Type PVC-76751E3XO, or Type PVC-77751E3XO in accordance with ASTM D 2287-81 (1988).
(iv)
Raw materials intended as conductor insulation furnished to these requirements shall be free from dirt, metallic particles, and other foreign matter.
(7)
A permissible overall performance level of faults in conductor insulation when using the test procedures in paragraph (b)(8) of this section shall average not greater than one fault per 12,000 conductor meters (40,000 conductor feet) for each gauge of conductor.
(8)
The test used to determine compliance with paragraph (b)(7) of this section shall be conducted as follows:
(i)
Samples tested shall be taken from finished cables selected at random from standard production cable. The samples tested shall contain a minimum of 300 conductor meters (1,000 conductor feet) for cables sizes less than 50 pairs and 1,500 conductor meters (5,000 conductor feet) for cables sizes greater than or equal to 50 pairs. No further sample need be taken from the same cable production run within 6,000 cable meters (20,000 cable feet) of the original test sample from that run.
(ii)
The cable sample shall have its jacket, shield, and core wrap removed and its core shall be immersed in tap water for a minimum period of 6 hours. In lieu of removing the jacket, shield, and core wrap from the core, the entire cable may be tested. In this case, the core shall be completely filled with tap water, under pressure; then the cable assembly shall be immersed for a minimum period of 6 hours. With the cable core still fully immersed, except for end connections, the insulation resistance (IR) of all conductors to water shall be measured using a direct current (dc) voltage of 100 volts to 550 volts.
(iii)
An IR value of less than 500 megohms for any individual insulated conductor tested at or corrected to a temperature of 23 °C is considered a failure. If the cable sample is more than 7.5 meters (25 feet) long, all failing conductors shall be retested and reported in 7.5 meter (25 foot) segments.
(iv)
The pair count, gauge, footage, and number of insulation faults shall be recorded. This information shall be retained on a 6 month running basis for review by RUS when requested.
(v)
A fault rate, in a continuous length in any one reel, in excess of one fault per 3,000 conductor meters (10,000 conductor feet) due to manufacturing defects is cause for rejection. A minimum of 6,000 conductor meters (20,000 conductor feet) is required to develop a noncompliance in a reel.
(9)
Repairs to the conductor insulation during manufacturing are permissible. The method of repair shall be accepted by RUS prior to its use. The repaired insulation shall be capable of meeting the relevant electrical requirements of this section.
(10)
All repaired sections of insulation shall be retested in the same manner as originally tested for compliance with paragraph (b)(7) of this section.
(11)
The colored composite insulating material removed from or tested on the conductor, from a finished cable, shall be capable of meeting the following performance requirements:
| Property | Composite insulation |
|---|---|
| Tensile Strength, Minimum Megapascals (MPa) (Pounds per square inch (psi)) | 16.5 (2400) |
| Ultimate Elongation Percent, Minimum | 125 |
| Cold Bend Failures, Maximum | 0/10 |
| Shrinkback, Maximum Millimeter (mm) (Inches (in.)) | 9.5 (3/8) |
| Adhesion, Maximum Newtons (N) (Pound-force (lbf)) | 13.3 (3) |
| Compression Minimum, N (lbf) | 1780 (400) |
(12) Testing procedures.
The procedures for testing the composite insulation samples for compliance with paragraph (b)(11) of this section shall be as follows:
(i) Tensile strength and ultimate elongation.
Samples of the insulation material, removed from the conductor, shall be tested in accordance with ASTM D 2633-82(1989), except that the speed of jaw separation shall be 50 millimeters/minute (50 mm/min) (2 inches/minute (2 in./min)).
Code of Federal Regulations
(ii) Cold bend.
Samples of the insulation material on the conductor shall be tested in accordance with ASTM D 4565-90a at a temperature of −40±1 °C with a mandrel diameter of 6 mm (0.25 in.). There shall be no cracks visible to normal or corrected-to-normal vision.
(iii) Shrinkback.
Samples of insulation shall be tested for four hours at a temperature of 115±1 °C in accordance with ASTM D 4565-90a.
(iv) Adhesion.
Samples of insulation material on the conductor shall be tested in accordance with ASTM D 4565-90a with a crosshead speed of 50 mm/min (2 in./min).
(v) Compression.
Samples of the insulation material on the conductor shall be tested in accordance with ASTM D 4565-90a with a crosshead speed of 5 mm/min (0.2 in./min).
(2)
The colors used to provide identification of the tip and ring conductor of each pair shall be as shown in the following table:
| Pair No. | Color | |
|---|---|---|
| Tip | Ring | |
| 1 | White | Blue |
| 2 | White | Orange |
| 3 | White | Green |
| 4 | White | Brown |
| 5 | White | Slate |
| 6 | Red | Blue |
| 7 | Red | Orange |
| 8 | Red | Green |
| 9 | Red | Brown |
| 10 | Red | Slate |
| 11 | Black | Blue |
| 12 | Black | Orange |
| 13 | Black | Green |
| 14 | Black | Brown |
| 15 | Black | Slate |
| 16 | Yellow | Blue |
| 17 | Yellow | Orange |
| 18 | Yellow | Green |
| 19 | Yellow | Brown |
| 20 | Yellow | Slate |
| 21 | Violet | Blue |
| 22 | Violet | Orange |
| 23 | Violet | Green |
| 24 | Violet | Brown |
| 25 | Violet | Slate |
(3) Standards of color.
The colors of the insulated conductors supplied in accordance with this section are specified in terms of the Munsell Color System (ASTM D 1535-89) and shall comply with the “Table of Wire and Cable Limit Chips” as defined in ANSI/EIA-359-A-84. (Visual color standards meeting these requirements may be obtained directly from the Munsell Color Company, Inc., 2441 North Calvert Street, Baltimore, Maryland 21218).
(4)
Positive identification of the tip and ring conductors of each pair by marking each conductor of a pair with the color of its mate is permissible. The method of marking shall be accepted by RUS prior to its use.
(5)
Other methods of providing positive identification of the tip and ring conductors of each pair may be employed if accepted by RUS prior to its use.
(7)
In order to provide sufficiently high crosstalk isolation, the pair twists shall be designed to enable the cable to meet the capacitance unbalance and the crosstalk loss requirements of paragraphs (h)(2), (h)(3), and (h)(4) of this section.
(8)
The average length of pair twists in any pair in the finished cable, when measured on any 3 meter (m) (10 foot (ft)) length, shall not exceed 152 mm (6 in.).
(d) Forming of the cable core.
(1)
Twisted pairs shall be assembled in such a way as to form a substantially cylindrical group.
(2)
When desired for lay-up reasons, the basic group may be divided into two or more subgroups called units.
(3)
Each group, or unit in a particular group, shall be enclosed in bindings of the colors indicated for its particular pair count. The pair count, indicated by the color of insulation, shall be consecutive as indicated in paragraph (d)(5) of this section through units in a group.
(4)
Threads or tapes used as binders shall be nonhygroscopic and nonwicking. The threads shall consists of a suitable number of ends of each color arranged as color bands. When tapes are used as binders, they shall be colored. Binders shall be applied with a lay of not more than 100 mm (4 in.). The colored binders shall be readily recognizable as the basic intended color and shall be distinguishable from all other colors.
(5)
The colors of the bindings and their significance with respect to pair count shall be as shown in the following table:
| Group No. | Color of bindings | Group pair count |
|---|---|---|
| 1 | White-Blue | 1-25 |
| 2 | White-Orange | 26-50 |
| 3 | White-Green | 51-75 |
| 4 | White-Brown | 76-100 |
| 5 | White-Slate | 101-125 |
| 6 | Red-Blue | 126-150 |
| 7 | Red-Orange | 151-175 |
| 8 | Red-Green | 176-200 |
| 9 | Red-Brown | 201-225 |
| 10 | Red-Slate | 226-250 |
| 11 | Black-Blue | 251-275 |
| 12 | Black-Orange | 276-300 |
| 13 | Black-Green | 301-325 |
| 14 | Black-Brown | 326-350 |
| 15 | Black-Slate | 351-375 |
| 16 | Yellow-Blue | 376-400 |
| 17 | Yellow-Orange | 401-425 |
| 18 | Yellow-Green | 426-450 |
| 19 | Yellow-Brown | 451-475 |
| 20 | Yellow-Slate | 476-500 |
| 21 | Violet-Blue | 501-525 |
| 22 | Violet-Orange | 526-550 |
| 23 | Violet-Green | 551-575 |
| 24 | Violet-Brown | 576-600 |
(7)
When desired for manufacturing reasons, two or more 25 pair groups may be bound together with nonhygroscopic and nonwicking threads or tapes into super-units. The group binders and the super-unit binders shall be colored such that the combination of the two binders shall positively identify each 25 pair group from every other 25 pair group in the cable.
| Pair No. | Binder color |
|---|---|
| 1-600 | White |
| 601-1200 | Red |
(e) Core wrap.
(1)
The core shall be completely covered with a layer of nonhygroscopic and nonwicking dielectric material. The core wrap shall be applied with an overlap.
(2)
The core wrap shall provide a sufficient heat barrier to prevent visible evidence of conductor insulation deformation or adhesion between conductors, caused by adverse heat transfer during the jacketing operation.
(3)
Engineering Information: If required for manufacturing reasons, white or uncolored binders of nonhygroscopic and nonwicking material may be applied over the core and/or core wrap.
(f) Shield.
(1)
An aluminum shield, plastic coated on one side, shall be applied longitudinally over the core wrap.
(2)
The shield may be applied over the core wrap with or without corrugations (smooth) and shall be bonded to the outer jacket.
(3)
The shield overlap shall be a minimum of 3 mm (0.125 in.) for cables with core diameters of 15 mm (0.625 in.) or less and a minimum of 6 mm (0.25 in.) for cables with core diameters greater than 15 mm (0.625 in.). The core diameter is defined as the diameter under the core wrap and binding.
(i)
Successive lengths of shielding tapes may be joined during the manufacturing process by means of cold weld, electric weld, soldering with a nonacid flux, or other acceptable means;
(ii)
The metal shield with the plastic coating shall have the coating removed prior to joining the metal ends together. After joining, the plastic coating shall be restored without voids using good manufacturing techniques;
(iii)
The shields of each length of cable shall be tested for continuity. A one meter (3 ft) section of shield containing a factory joint shall exhibit not more than 110 percent of the resistance of a shield of equal length without a joint;
(iv)
The breaking strength of any section of a shield tape containing a factory joint shall not be less than 80 percent of the breaking strength of an adjacent section of the shield of equal length without a joint;
(v)
The reduction in thickness of the shielding material due to the corrugating or application process shall be kept to a minimum and shall not exceed 10 percent at any spot; and
(vi)
The shielding material shall be applied in such a manner as to enable the cable to pass the bend test as specified in paragraph (i)(1) of this section.
(6)
The aluminum tape shall conform to either Alloy AA-1100-0, AA-1145-0, or AA-1235-0 as covered in the latest edition of Aluminum Standards and Data, issued by the Aluminum Association, except that requirements for tensile strength are waived.
(7)
The single-sided plastic coated aluminum shield shall conform to the requirements of ASTM B 736-92a, Type I Coating, Class 1 or 2, or Type II Coating, Class 1. The minimum thickness of the Type I Coating shall be 0.038 mm (0.0015 in.). The minimum thickness of the Type II Coating shall be 0.008 mm (0.0003 in.).
(8)
The plastic coated aluminum shield shall be tested for resistance to water migration by immersing a one meter (3 ft) length of tape under a one meter (3 ft) head of water containing a soluble dye plus 0.25 percent (%) wetting agent.
(i)
After a minimum of 5 minutes, no dye shall appear between the interface of the shield tape and the plastic coating.
(9)
The bond between the plastic coated shield and the jacket shall conform to the following requirements:
(i)
Prepare test strips approximately 200 mm (8 in.) in length. Slit the jacket and shield longitudinally to produce 4 strips evenly spaced and centered in 4 quadrants on the jacket circumference. One of the strips shall be centered over the overlapped edge of the shielding tape. The strips shall be 13 mm (0.5 in.) wide. For cable diameters less than 19 mm (0.75 in.) make two strips evenly spaced.
(ii)
Separate the shield and jacket for a sufficient distance to allow the shield and jacket to be fitted in the upper and lower jaws of a tensile machine. Record the maximum force required to separate the shield and jacket to the nearest newton (pound-force). Repeat this action for each test strip.
(iii)
The force required to separate the jacket from the shield shall not be less than 9 N (2 lbf) for any individual strip when tested in accordance with paragraph (f)(9)(ii) of this section. The average force for all strips of any cable shall not be less than 18 N (4 lbf).
(g) Cable jacket and extraneous material.
(1)
The jacket shall provide the cable with a tough, flexible, protective covering which can withstand stresses reasonably expected in normal installation and service.
(2)
The jacket shall be free from holes, splits, blisters, or other imperfections and shall be as smooth and concentric as is consistent with the best commercial practice.
(4)
The jacketing material removed from or tested on the cable shall be capable of meeting the following performance requirements:
| Property | Jacket performance |
|---|---|
| Tensile Strength-Unaged Minimum, MPa (psi) | 13.8 (2000) |
| Ultimate Elongation-Unaged Minimum, Percent (%) | 200 |
| Tensile Strength-Aged Minimum, % of original value | 80 |
| Ultimate Elongation-Aged Minimum, % of original value | 50 |
| Impact Failures, Maximum | 2/10 |
(5) Testing procedures.
The procedures for testing the jacket samples for compliance with paragraph (g)(4) of this section shall be as follows:
(i) Tensile strength and ultimate elongation-unaged.
The test shall be performed in accordance with ASTM D 2633-82(1989), using a jaw separation speed of 50 mm/min (2 in./min).
Code of Federal Regulations
(ii) Tensile strength and ultimate elongation-aged.
The test shall be performed in accordance with paragraph (g)(5)(i) of this section after being aged for 7 days at a temperature of 100±1 °C in a circulating air oven conforming to ASTM D 2436-85.
(iii) Impact.
The test shall be performed in accordance with ASTM D 4565-90a using an impact force of 4 newton-meter (3 pound force-foot) at a temperature of −10±1 °C. The cylinder shall strike the sample at the shield overlap. A crack or split in the jacket constitutes failure.
(6) Jacket thickness.
The nominal jacket thickness shall be as specified in the following table. The test method used shall be either the End Sample Method (paragraph (g)(6)(i) of this section) or the Continuous Uniformity Thickness Gauge Method (paragraph (g)(6)(ii) of this section):
| No. of pairs | Nominal jacket thickness mm (in.) |
|---|---|
| 25 or less | 1.4 (0.055) |
| 50 | 1.5 (0.060) |
| 100 | 1.7 (0.065) |
| 200 | 1.9 (0.075) |
| 300 | 2.2 (0.085) |
| 400 | 2.4 (0.095) |
| 600 | 2.9 (0.115) |
| 800 and over | 3.3 (0.130) |
Minimum Average Thickness—90% of nominal thickness
Minimum Thickness—70% of nominal thickness
(ii) Continuous uniformity thickness gauge method.
(A)
The jacket shall be capable of meeting the following requirements:
Minimum Average Thickness—90% of nominal thickness
Minimum (Min.) Thickness—70 % of nominal thickness
Maximum (Max.) Eccentricity—55%
Eccentricity=Max. Thickness—Min. Thickness (Average Thickness)×100
(B) Maximum and minimum thickness values.
The maximum and minimum thickness values shall be based on the average of each axial section.
(7)
The color of the jacket shall be either black or dark grey in conformance with the Munsell Color System specified in ASTM D 1535-89.
(8)
There shall be no water or other contaminants in the finished cable which would have a detrimental effect on its performance or its useful life.
(h) Electrical requirements—
(1) Mutual capacitance and conductance.
The average mutual capacitance (corrected for length) of all pairs in any reel shall not exceed the following when tested in accordance with ASTM D 4566-90 at a frequency of 1.0±0.1 kilohertz (kHz) and a temperature of 23±3 °C:
| Number of cable pairs | Mutual capacitance | |
|---|---|---|
| Nanofarad/kilometer | (Nanofarad/mile) | |
| 12 | 52±4 | (83±7) |
| Over 12 | 52±2 | (83±4) |
(ii)
The root mean square (rms) deviation of the mutual capacitance of all pairs from the average mutual capacitance of that reel shall not exceed 3.0 % when calculated in accordance with ASTM D 4566-90.
(iii)
The mutual conductance (corrected for length and gauge) of any pair shall not exceed 3.7 micromhos/kilometer (micromhos/km) (6.0 micromhos/mile) when tested in accordance with ASTM D 4566-90 at a frequency of 1.0±0.1 kHz and a temperature of 23±3 °C.
(2) Pair-to-pair capacitance unbalance.
The capacitance unbalance as measured on the completed cable shall not exceed 45.3 picofarad/kilometer (pF/km) (25 picofarad/1000 ft (pF/1000 ft)) rms when tested in accordance with ASTM D 4566-90 at a frequency of 1.0±0.1 kHz and a temperature of 23±3 °C.
(3) Pair-to-ground capacitance unbalance.
(i)
The average capacitance unbalance as measured on the completed cable shall not exceed 574 pF/km (175 pF/1000 ft) when tested in accordance with ASTM D 4566-90 at a frequency of 1±0.1 kHz and a temperature of 23±3 °C.
(ii)
When measuring pair-to-ground capacitance unbalance all pairs except the pair under test are grounded to the shield except when measuring cable containing super-units in which case all other pairs in the same super-unit shall be grounded to the shield.
(4) Crosstalk loss.
(i)
The rms output-to-output far-end crosstalk loss (FEXT) measured on the completed cable in accordance with ASTM D 4566-90 at a test frequency of 150 kHz shall not be less than 68 decibel/kilometer (dB/km) (73 decibel/1000 ft (dB/1000 ft)). The rms calculation shall be based on the combined total of all adjacent and alternate pair combinations within the same layer and center to first layer pair combinations.
(ii)
The FEXT crosstalk loss between any pair combination of a cable shall not be less than 58 dB/km (63 dB/1000 ft) at a frequency of 150 kHz. If the loss Ko at a frequency Fo for length Lo is known, then Kx can be determined for any other frequency Fx or length Lx by:
(iii)
The near-end crosstalk loss (NEXT) as measured within and between units of a completed cable in accordance with ASTM D 4566-90 at a frequency of 772 kHz shall not be less than the following mean minus sigma (M-S) crosstalk requirement for any unit within the cable:
| Unit size | M-S decibel (dB) |
|---|---|
| Within Unit: | |
| 12 and 13 pairs | 56 |
| 18 and 25 pairs | 60 |
| Between Unit: | |
| Adjacent 13 pairs | 65 |
| Adjacent 25 pairs | 66 |
| Nonadjacent (all) | 81 |
Where M-S is the Mean near-end coupling loss based on the combined total of all pair combinations, less one Standard Deviation, Sigma, of the mean value.
(5) Insulation resistance.
Each insulated conductor in each length of completed cable, when measured with all other insulated conductors and the shield grounded, shall have an insulation resistance of not less than 152 megohm-kilometer (500 megohm-mile) at 20±1 °C. The measurement shall be made in accordance with the procedures of ASTM D 4566-90.