1755.390—RUS specification for filled telephone cables.
(a) Scope.
(1)
This section covers the requirements for filled telephone cables intended for direct burial installation either by trenching or by direct plowing, for underground application by placement in a duct, or for aerial installations by attachment to a support strand.
(i)
The conductors are solid copper, individually insulated with an extruded solid insulating compound.
(ii)
The insulated conductors are twisted into pairs which are then stranded or oscillated to form a cylindrical core.
(iii)
For high frequency applications, the cable core may be separated into compartments with screening shields.
(iv)
A moisture resistant filling compound is applied to the stranded conductors completely covering the insulated conductors and filling the interstices between pairs and units.
(v)
The cable structure is completed by the application of suitable core wrapping material, a flooding compound, a shield or a shield/armor, and an overall plastic jacket.
(2)
The number of pairs and gauge size of conductors which are used within the RUS program are provided in the following table:
| AWG | 19 | 22 | 24 | 26 |
| Pairs | 6 | 6 | 6 | |
| 12 | 12 | 12 | ||
| 18 | 18 | 18 | ||
| 25 | 25 | 25 | 25 | |
| 50 | 50 | 50 | ||
| 75 | 75 | 75 | ||
| 100 | 100 | 100 | ||
| 150 | 150 | 150 | ||
| 200 | 200 | 200 | ||
| 300 | 300 | 300 | ||
| 400 | 400 | 400 | ||
| 600 | 600 | |||
| 900 | ||||
| Note: Cables larger in pair sizes than those shown in this table must meet all requirements of this section. | ||||
(3)
Screened cable, when specified, must meet all requirements of this section. The pair sizes of screened cables used within the RUS program are referenced in paragraph (e)(2)(i) of this section.
(4)
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.
(5)
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 must be provided to substantiate product utility and long-term stability and endurance.
(6)
The American National Standard Institute/Insulated Cable Engineers Association, Inc. (ANSI/ICEA) S-84-608-1988 Standard For Telecommunications Cable, Filled, Polyolefin Insulated, Copper Conductor Technical Requirements referenced throughout 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/ICEA S-84-608-1988 are available for inspection during normal business hours at RUS, room 2845, U.S. Department of Agriculture, Washington, DC 20250, 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 ICEA, P. O. Box 440, South Yarmouth, MA 02664, telephone number (508) 394-4424.
(7)
American Society for Testing and Materials specifications (ASTM) A 505-87, Standard Specification for Steel, Sheet and Strip, Alloy, Hot-Rolled and Cold-Rolled, General Requirements For; ASTM B 193-87, Standard Test Method for Resistivity of Electrical Conductor Materials; ASTM B 224-80, Standard Classification of Coppers; ASTM B 694-86, Standard Specification for Copper, Copper Alloy, and Copper-Clad Stainless Steel Sheet and Strip for Electrical Cable Shielding; ASTM D 4565-90a, Standard Test Methods for Physical and Environmental Performance Properties of Insulations and Jackets for Telecommunications Wire and Cable; and ASTM D 4566-90, Standard Test Methods for Electrical Performance Properties of Insulations and Jackets for Telecommunications Wire and Cable 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, 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, PA 19103-1187, telephone number (215) 299-5585.
(b) Conductors and conductor insulation.
(1)
The gauge sizes of the copper conductors covered by this specification must be 19, 22, 24, and 26 American Wire Gauge (AWG).
(2)
Each conductor must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 2.1.
(3)
Factory joints made in conductors during the manufacturing process must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 2.2.
(4)
The raw materials used for conductor insulation must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 3.1 through 3.1.3.
(5)
The finished conductor insulation must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 3.2.1 and 3.3.
(6)
Insulated conductors must not have an overall diameter greater than 2 millimeters (mm) (0.081 inch (in.)).
(7)
A permissible overall performance level of faults in conductor insulation must average not greater than one fault per 12,000 conductor meters (40,000 conductor feet) for each gauge of conductor.
(i)
All insulated conductors must be continuously tested for insulation faults during the twinning operation with a method of testing acceptable to RUS. The length count and number of faults must be recorded. The information must be retained for a period of 6 months and be available for review by RUS when requested.
| AWG | Direct Current Voltages (kilovolts) |
|---|---|
| 19 | 8.0 |
| 22 | 6.0 |
| 24 | 5.0 |
| 26 | 4.0 |
(8)
Repairs to the conductor insulation during manufacture are permissible. The method of repair must be accepted by RUS prior to its use. The repaired insulation must be capable of meeting the relevant electrical requirements of this section.
(9)
All repaired sections of insulation must be retested in the same manner as originally tested for compliance with paragraph (b)(7) of this section.
(10)
The colored insulating material removed from or tested on the conductor, from a finished cable, must meet the performance requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 3.4.1, 3.4.2, 3.4.4, 3.4.5, and 3.4.6.
(2)
The colors to be used in the pairs in the 25 pair group, together with the pair numbers must be in accordance with the table specified in ANSI/ICEA S-84-608-1988, paragraph 3.5.
(3)
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 must be accepted by RUS prior to its use.
(4)
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.
(6)
In order to provide sufficiently high crosstalk isolation, the pair twists must be designed to enable the cable to meet the capacitance unbalance and crosstalk loss requirements of paragraphs (k)(5), (k)(6), and (k)(8) of this section.
(7)
The average length of pair twists in any pair in the finished cable, when measured on any 3 meter (10 foot) length, must not exceed the requirement specified in ANSI/ICEA S-84-608-1988, paragraph 3.5.
(d) Forming of the cable core.
(1)
Twisted pairs must 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, must be enclosed in bindings of the colors indicated for its particular pair count. The pair count, indicated by the colors of insulation, must be consecutive as indicated in paragraph (d)(6) of this section through units in a group.
(4)
The filling compound must be applied to the cable core in such a way as to provide as near a completely filled core as is commercially practical.
(5)
Threads and tapes used as binders must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 4.2 and 4.2.1.
(6)
The colors of the bindings and their significance with respect to pair count must be as follows:
| 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 |
(8)
When desired for manufacturing reasons, two or more 25 pair groups may be bound together with nonhygroscopic and nonwicking threads or tapes into a super-unit. Threads or tapes must meet the requirements specified in paragraph (d)(5) of this section. The group binders and the super-unit binders must be color coded such that the combination of the two binders must positively identify each 25 pair group from every other 25 pair group in the cable. Super-unit binders must be of the color shown in the following table:
| Pair Numbers | Binder Color |
|---|---|
| 1-600 | White |
| 601-1200 | Red |
| 1201-1800 | Black |
| 1801-2400 | Yellow |
| 2401-3000 | Violet |
(9)
Color binders must not be missing for more than 90 meters (300 feet) from any 25 pair group or from any subgroup used as part of a super-unit. At any cable cross-section, no adjacent 25 pair groups and no more than one subgroup of any super-unit may have missing binders. In no case must the total number of missing binders exceed three. Missing super-unit binders must not be permitted for any distance.
(10)
Any reel of cable which contains missing binders must be labeled indicating the colors and location of the binders involved. The labeling must be applied to the reel and also to the cable.
(e) Screened cable.
(1)
Screened cable must be constructed such that a metallic, internal screen(s) must be provided to separate and provide sufficient isolation between the compartments to meet the requirements of this section.
(2)
At the option of the user or manufacturer, identified service pairs providing for voice order and fault location may be placed in screened cables.
(i)
The number of service pairs provided must be one per twenty-five operating pairs plus two for a cable size up to and including 400 pairs, subject to a minimum of four service pairs. The pair counts for screened cables are as follows:
| Carrier Pair Count | Service Pairs | Total Pair Count |
|---|---|---|
| 24 | 4 | 28 |
| 50 | 4 | 54 |
| 100 | 6 | 106 |
| 150 | 8 | 158 |
| 200 | 10 | 210 |
| 300 | 14 | 314 |
| 400 | 18 | 418 |
(ii)
The service pairs must be equally divided among the compartments. The color sequence must be repeated in each compartment.
(iii)
The electrical and physical characteristics of each service pair must meet all the requirements set forth in this section.
(iv)
The colors used for the service pairs must be in accordance with the requirements of paragraph (b)(5) of this section. The color code used for the service pairs together with the service pair number are shown in the following table:
| Service Pair No. | Color | |
|---|---|---|
| Tip | Ring | |
| 1 | White | Red |
| 2 | ” | Black |
| 3 | ” | Yellow |
| 4 | ” | Violet |
| 5 | Red | Black |
| 6 | ” | Yellow |
| 7 | ” | Violet |
| 8 | Black | Yellow |
| 9 | ” | Violet |
(3)
The screen tape must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 5.1 through 5.4.
(4)
The screen tape must be tested for dielectric strength by completely removing the protective coating from one end to be used for grounding purposes.
(i)
Using an electrode, over a 30 centimeter (1 foot) length, apply a direct current voltage at the rate of rise of 500 volts/second until failure.
(f) Filling compound.
(1)
After or during the stranding operation and prior to application of the core wrap, filling compound must be applied to the cable core. The compound must be as nearly colorless as is commercially feasible and consistent with the end product requirements and pair identification.
(2)
The filling compound must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 4.4 through 4.4.4.
(3)
The individual cable manufacturer must satisfy RUS that the filling compound selected for use is suitable for its intended application. The filling compound must be applied to the cable in such a manner that the cable components will not be degraded.
(g) Core wrap.
(1)
The core wrap must comply with the requirements specified in ANSI/ICEA-S-84-608-1988, paragraph 4.3.
(2)
If required for manufacturing reasons, white or colored binders of nonhygroscopic and nonwicking material may be applied over the core and/or wrap. When used, binders must meet the requirements specified in paragraph (d)(5) of this section.
(3)
Sufficient filling compound must be applied to the core wrap so that voids or air spaces existing between the core and the inner side of the core wrap are minimized.
(h) Flooding compound.
(1)
Sufficient flooding compound must be applied on all sheath interfaces so that voids and air spaces in these areas are minimized. When the optional armored design is used, the flooding compound must be applied between the core wrap and shield, between the shield and armor, and between the armor and the jacket so that voids and air spaces in these areas are minimized. The use of floodant over the outer metallic substrate is not required if uniform bonding, per paragraph (i)(7) of this section, is achieved between the plastic-clad metal and the jacket.
(2)
The flooding compound must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 4.5 and the jacket slip test requirements of appendix A, paragraph (III)(5) of this section.
(3)
The individual cable manufacturer must satisfy RUS that the flooding compound selected for use is acceptable for the application.
(i) Shield and optional armor.
(1)
A single corrugated shield must be applied longitudinally over the core wrap.
(2)
For unarmored cable the shield overlap must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.3.2. Core diameter is defined as the diameter under the core wrap and binding.
(3)
For cables containing the coated aluminum shield/coated steel armor (CACSP) sheath design, the coated aluminum shield must be applied in accordance with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.3.2, Dual Tape Shielding System.
(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)
Shield splices must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.3.3.
(iii)
The corrugations and the application process of the coated aluminum and copper bearing shields must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.3.1.
(iv)
The shielding material must be applied in such a manner as to enable the cable to pass the cold bend test specified in paragraph (l)(3) of this section.
(5)
The following is a list of acceptable materials for use as cable shielding. Other types of shielding materials may also be used provided they are accepted by RUS prior to their use.
| Standard Cable | Gopher Resistant Cable |
|---|---|
| 8-mil Coated Aluminum 1 | 10-mil Copper |
| 5-mil Copper | 6-mil Copper-CladStainless Steel 5 mil Copper-Clad Stainless Steel 5 mil Copper-Clad Alloy Steel 7-mil Alloy 194 6-mil Alloy 194 8-mil Coated Aluminum 1 and 6-mil Coated Steel 1 |
| 1 Dimensions of uncoated metal | |
(i)
The 8-mil aluminum tape must be plastic coated on both sides and must comply with the requirements of ANSI/ICEA S-84-608-1988, paragraph 6.2.2.
(ii)
The 5-mil copper tape must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.2.3.
(iii)
The 10-mil copper tape must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.2.4.
(iv)
The 6-mil copper clad stainless steel tape must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.2.5.
(v)
The 5-mil copper clad stainless steel tape must be in the fully annealed condition and must conform to the requirements of American Society for Testing and Materials (ASTM) B 694-86, with a cladding ratio of 16/68/16.
(A)
The electrical conductivity of the clad tape must be a minimum of 28 percent of the International Annealed Copper Standard (IACS) when measured per ASTM B 193-87.
(B)
The tape must be nominally 0.13 millimeter (0.005 inch) thick with a minimum thickness of 0.11 millimeter (0.0045 inch).
(vi)
The 5-mil copper clad alloy steel tape must be in the fully annealed condition and the copper component must conform to the requirements of ASTM B 224-80 and the alloy steel component must conform to the requirements of ASTM A 505-87, with a cladding ratio of 16/68/16.
(A)
The electrical conductivity of the copper clad alloy steel tape must comply with the requirement specified in paragraph (i)(5)(v)(A) of this section.
(B)
The thickness of the copper clad alloy steel tape must comply with the requirements specified in paragraph (i)(5)(v)(B) of this section.
(vii)
The 6-mil and 7-mil 194 copper alloy tapes must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.2.6.
(6)
The corrugation extensibility of the coated aluminum shield must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.4.
(7)
When the jacket is bonded to the plastic coated aluminum shield, the bond between the jacket and shield must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 7.2.6.
(8)
A single plastic-coated steel corrugated armor must be applied longitudinally directly over the coated aluminum shield listed in paragraph (i)(5) of this section with an overlap complying with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.3.2, Outer Steel Tape.
(9)
Successive lengths of steel armoring tapes may be joined during the manufacturing process by means of cold weld, electric weld, soldering with a nonacid flux, or other acceptable means. Armor splices must comply with the breaking strength and resistance requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.3.3.
(10)
The corrugations and the application process of the coated steel armor must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.3.1.
(i)
The corrugations of the armor tape must coincide with the corrugations of the coated aluminum shield.
(ii)
Overlapped portions of the armor tape must be in register (corrugations must coincide at overlap) and in contact at the outer edge.
(11)
The armoring material must be so applied to enable the cable to pass the cold bend test as specified in paragraph (l)(3) of this section.
(12)
The 6-mil steel tape must be electrolytic chrome-coated steel (ECCS) plastic coated on both sides and must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 6.2.8.
(13)
When the jacket is bonded to the plastic-coated steel armor, the bond between the jacket and armor must comply with the requirement specified in ANSI/ICEA-S-84-608-1988, paragraph 7.2.6.
(j) Cable jacket.
(1)
The jacket must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 7.2.
(2)
The raw materials used for the cable jacket must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 7.2.1.
(3)
Jacketing material removed from or tested on the cable must meet the performance requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 7.2.3 and 7.2.4.
(4)
The thickness of the jacket must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 7.2.2.
(k) Electrical requirements—
(1) Conductor resistance.
The direct current resistance of any conductor in a completed cable and the average resistance of all conductors in a Quality Control Lot must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.1.
(2) Resistance unbalance.
(i)
The direct current resistance unbalance between the two conductors of any pair in a completed cable and the average resistance unbalance of all pairs in a completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.2.
(ii)
The resistance unbalance between tip and ring conductors shall be random with respect to the direction of unbalance. That is, the resistance of the tip conductors shall not be consistently higher with respect to the ring conductors and vice versa.
(3) Mutual capacitance.
The average mutual capacitance of all pairs in a completed cable and the individual mutual capacitance of any pair in a completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.3.
(4) Capacitance difference.
(i)
The capacitance difference for completed cables having 75 pairs or greater must comply with the requirement specified in ANSI/ICEA S-84-608-1988, paragraph 8.4.
(ii)
When measuring screened cable, the inner and outer pairs must be selected from both sides of the screen.
(5) Pair-to-pair capacitance unbalance—
(i) Pair-to-pair.
The capacitance unbalance as measured on the completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.5.
(ii) Screened cable.
In cables with 25 pairs or less and within each group of multigroup cables, the pair-to-pair capacitance unbalance between any two pairs in an individual compartment must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.5. The pair-to-pair capacitance unbalances to be considered must be:
(C)
Between pairs in adjacent layers in an individual compartment when the number of pairs in the inner (smaller) layer is 6 or less. The center is counted as a layer.
(iii)
In cables with 25 pairs or less, the root-mean-square (rms) value must include all the pair-to-pair unbalances measured for each compartment separately.
(iv)
In cables containing more than 25 pairs, the rms value must include the pair-to-pair unbalances in the separate compartments.
(6) Pair-to-ground capacitance unbalance—
(i) Pair-to-ground.
The capacitance unbalance as measured on the completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.6.
(ii)
When measuring pair-to-ground capacitance unbalance all pairs except the pair under test are grounded to the shield and/or shield/armor except when measuring cables containing super units in which case all other pairs in the same super unit must be grounded to the shield.
(7) Attenuation.
(i)
For nonscreened and screened cables, the average attenuation of all pairs on any reel when measured at 150 and 772 kilohertz must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.7, Solid Column.
(ii)
For T1C type cables over 12 pairs, the maximum average attenuation of all pairs on any reel must not exceed the values listed below when measured at a frequency of 1576 kilohertz at or corrected to a temperature of 20 ±1 °C. The test must be conducted in accordance with ASTM D 4566-90.
| AWG | Maximum Average Attenuation decibel/kilometer (dB/km) (decibel/mile) |
|---|---|
| 19 | 13.4 (21.5) |
| 22 | 18.3 (29.4) |
| 24 | 23.1 (37.2) |
(8) Crosstalk loss.
(i)
The equal level far-end power sum crosstalk loss (FEXT) as measured on the completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.8, FEXT Table.
(ii)
The near-end power sum crosstalk loss (NEXT) as measured on completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.8, NEXT Table.
(iii) Screened cable.
(A)
For screened cables the NEXT as measured on the completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 8.9 and 8.9.1.
(B)
For T1C screened cable the NEXT as measured on the completed cable must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraphs 8.9 and 8.9.2.
(9) Insulation resistance.
The insulation resistance of each insulated conductor in a completed cable must comply with the requirement specified in ANSI/ICEA S-84-608-1988, paragraph 8.11.
(10) High voltage test.
(i)
In each length of completed cable, the insulation between conductors must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.12, Solid Column.
(ii)
In each length of completed cable, the dielectric between the shield and/or armor and conductors in the core must comply with the requirements specified in ANSI/ICEA S-84-608-1988, paragraph 8.13, Single Jacketed, Solid Column. In screened cable the screen tape must be left floating.
(iii) Screened cable.
(A)
In each length of completed screened cable, the dielectric between the screen tape and the conductors in the core must comply with the requirement specified in ANSI/ICEA S-84-608-1988, paragraph 8.14.
(11) Electrical variations.
(i)
Pairs in each length of cable having either a ground, cross, short, or open circuit condition will not be permitted.
(ii)
The maximum number of pairs in a cable which may vary as specified in paragraph (k)(11)(iii) of this section from the electrical parameters given in this section are listed below. These pairs may be excluded from the arithmetic calculation.
| Nominal Pair Count | Maximum Number of Pairs With Allowable Electrical Variation |
|---|---|
| 6-100 | 1 |
| 101-300 | 2 |
| 301-400 | 3 |
| 401-600 | 4 |
| 601 and above | 6 |
(iii) Parameter variations.
(A) Capacitance unbalance-to-ground.
If the cable fails either the maximum individual pair or average capacitance unbalance-to-ground requirement and all individual pairs are 3937 picofarad/kilometer (1200 picofarad/1000 feet) or less, the number of pairs specified in paragraph (k)(11)(ii) of this section may be eliminated from the average and maximum individual calculations.
| AWG | ohms/kilometer | (ohms/1000 feet) |
|---|---|---|
| 19 | 29.9 | ( 9.1) |
| 22 | 60.0 | (18.3) |
| 24 | 94.5 | (28.8) |
| 26 | 151.6 | (46.2) |
| Note: RUS recognizes that in large pair count cable (600 pair and above) a cross, short or open circuit condition occasionally may develop in a pair which does not affect the performance of the other cable pairs. In these circumstances rejection of the entire cable may be economically unsound or repairs may be impractical. In such circumstances the manufacturer may desire to negotiate with the customer for acceptance of the cable. No more than 0.5 percent of the pairs may be involved. | ||