[Federal Register Volume 62, Number 85 (Friday, May 2, 1997)]
[Rules and Regulations]
[Pages 23958-24008]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-11316]
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DEPARTMENT OF AGRICULTURE
Rural Utilities Service
7 CFR Part 1755
RUS Standard for Acceptance Tests and Measurements of
Telecommunications Plant
AGENCY: Rural Utilities Service, USDA.
ACTION: Final rule.
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SUMMARY: The Rural Utilities Service (RUS) amends its regulations on
Telecommunications Standards and Specifications for Materials,
Equipment and Construction, by rescinding RUS Bulletin 345-63, RUS
Standard for Acceptance Tests and Measurements of Telephone Plant, PC-
4, and codifying the revised RUS standard at 7 CFR 1755.400 through 7
CFR 1755.407, in the Code of Federal Regulations. The revised standard:
Updates the acceptance tests and measurements for copper conductor
telecommunications plant; includes a section on acceptance tests and
measurements for fiber optic cable plant; includes a section on
acceptance tests and measurements for voiceband data transmission; and
includes a shield or armor ground resistance test to determine outer
jacket cable damage.
DATES: Effective date: June 2, 1997.
Incorporation by reference: Incorporation by reference of certain
publications listed in this final rule is approved by the Director of
the Federal Register as of June 2, 1997.
FOR FURTHER INFORMATION CONTACT: Charlie I. Harper, Jr., Chief, Outside
Plant Branch, Telecommunications Standards Division, Rural Utilities
Service, room 2837, STOP 1598, South Building, U.S. Department of
Agriculture, Washington, DC 20250-1598, telephone number (202) 720-
0667.
SUPPLEMENTARY INFORMATION:
Executive Order 12866
This final rule has been determined to be not significant and
therefore has not been reviewed by the Office of Management and Budget.
Executive Order 12988
This final rule has been reviewed under Executive Order 12988,
Civil Justice Reform. RUS has determined that this final rule meets the
applicable standards provided in section 3 of that Executive Order.
Regulatory Flexibility Act Certification
The Administrator of RUS has determined that this final rule will
not have a significant economic impact on a substantial number of small
entities, as defined by the Regulatory Flexibility Act (5 U.S.C. 601 et
seq.). This final rule involves standards and specifications, which may
increase the direct short-term costs to RUS borrowers. However, the
long-term direct economic costs are reduced through greater durability
and lower maintenance cost over time.
Information Collection and Recordkeeping Requirements
The reporting and recordkeeping requirements contained in the final
rule were approved by the Office of Management and Budget (OMB)
pursuant to the Paperwork Reduction Act of 1995 (44 U.S.C. Chapter 35,
as amended) under control number 0572-0059.
Send questions or comments regarding this burden or any aspect of
these collections of information, including suggestions for reducing
the burden, to F. Lamont Heppe, Jr., Director, Program Support and
Regulatory Analysis, Rural Utilities Service, U.S. Department of
Agriculture,
[[Page 23959]]
Stop 1522, Washington, DC 20250-1522, Fax: (202) 720-4120.
National Environmental Policy Act Certification
The Administrator of RUS has determined that this final rule will
not significantly affect the quality of the human environment as
defined by the National Environmental Policy Act of 1969 (42 U.S.C.
4321 et seq.) Therefore, this action does not require an environmental
impact statement or assessment.
Catalog of Federal Domestic Assistance
The program described by this final rule is listed in the Catalog
of Federal Domestic Assistance programs under No. 10.851, Rural
Telephone Loans and Loan Guarantees; and No. 10.852, Rural Telephone
Bank Loans. This catalog is available on a subscription basis from the
Superintendent of Documents, the United States Government Printing
Office, Washington, DC 20402.
Executive Order 12372
This final rule is excluded from the scope of Executive Order
12372, Intergovernmental Consultation, which may require consultation
with State and local officials. A Notice of Final rule titled
Department Programs and Activities Excluded from Executive Order 12372
(50 FR 47034) exempts RUS and RTB loans and loan guarantees, and RTB
bank loans, to governmental and nongovernmental entities from coverage
under this Order.
Background
RUS issues publications titled ``Bulletin'' which serve to guide
borrowers regarding already codified policy, procedures, and
requirements needed to manage loans, loan guarantee programs, and the
security instruments which provide for and secure RUS financing. RUS
issues standards and specifications for the construction of telephone
facilities financed with RUS Loan Funds. RUS is rescinding Bulletin
345-63, ``RUS Standard for Acceptance Tests and Measurements of
Telephone Plant, PC-4,'' and to codifying this standard in 7 CFR
1755.400 through 7 CFR 1755.407, RUS Standard for Acceptance Tests and
Measurements of Telecommunications Plant.
This standard is used to determine the acceptability of installed
telecommunications plant. The current standard with regard to copper
cable plant acceptance tests and measurements has become outdated as a
result of technological advancements made in copper cable plant
acceptance test methods during the past fourteen years. Therefore to
assure RUS borrowers that their installed copper cable plant is of the
highest quality, the revised standard will update acceptance test and
measurement methods for copper cable plant.
There is currently a need to include into the standard a section
dealing with standardized test methods and measurements for installed
fiber optic cable plant. Presently acceptance test methods and
measurements for fiber optic cable plant are developed by each
consulting engineer resulting in a variety of test methods and
measurements which in turn results in higher construction costs to RUS
borrowers. By providing standardized acceptance test methods and
measurements for fiber optic cable plant, RUS will be assisting its
borrowers by decreasing their construction costs for fiber optic cable
installation.
There is currently a need to include into the standard a section
dealing with standardized test methods and measurements for voiceband
data transmission. Because RUS borrowers are increasing their usage of
modems to transmit data over telecommunications transmission
facilities, standardized test methods and measurements are needed to
ensure that the transmission facilities are acceptable for data
transmission.
There is presently a need to include into the current standard a
standardized shield or armor ground resistance test method and a
minimum requirement to determine when the outer cable jacket is damaged
as a result of the installation procedures. This standard test method
and minimum requirement will result in cost savings to RUS borrowers
because the variety of test methods and minimum requirements presently
being used by consulting engineers and contractors will be eliminated.
This action establishes RUS standardized acceptance test methods
and measurements to determine acceptability of installed
telecommunications plant. These standardized acceptance test methods
and measurements will afford RUS telephone borrowers an economical and
efficient means of reducing their construction costs.
On August 28, 1996, RUS published a proposed rule (61 FR 44195) to
rescind RUS Bulletin 345-63, RUS Standard for Acceptance Tests and
Measurements of Telephone Plant, PC-4, and to codify the revised RUS
Standard for Acceptance Tests and Measurements of Telecommunications
Plant in 7 CFR 1755.400 through 7 CFR 1755.407. Comments on this
proposed rule were due October 28, 1996. No comments were received by
this due date.
List of Subjects in 7 CFR Part 1755
Incorporation by reference, Loan programs--communications,
Reporting and recordkeeping requirements, Rural areas, Telephone.
For the reasons set out in the preamble, RUS amends chapter XVII of
title 7 of the Code of Federal Regulations as follows:
Part 1755--Telecommunications Standards and Specifications for
Materials, Equipment and Construction
1. The authority citation for part 1755 continues to read as
follows:
Authority: 7 U.S.C. 901 et seq., 1921 et seq., 6941 et seq.
Sec. 1755.97 [Amended]
2. Section 1755.97 is amended by removing the entry RUS Bulletin
345-63 from the table.
3. Section 1755.98 is amended by adding the entry 1755.400 through
1755.407 to the table in numerical order to read as follows:
Sec. 1755.98 List of telephone standards and specifications included
in other 7 CFR parts.
* * * * *
------------------------------------------------------------------------
Section Issue date Title
------------------------------------------------------------------------
* * * *
* * *
1755.400 through 1755.407... [Effective date of RUS Standard for
final rule]. Acceptance Tests
and Measurements of
Telecommunications
Plant.
* * * *
* * *
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[[Page 23960]]
4. Sections 1755.400 through 1755.407 are added to read as follows:
Sec. 1755.400 RUS standard for acceptance tests and measurements of
telecommunications plant.
Sections 1755.400 through 1755.407 cover the requirements for
acceptance tests and measurements on installed copper and fiber optic
telecommunications plant and equipment.
Sec. 1755.401 Scope.
(a) Acceptance tests outlined in Secs. 1755.400 through 1755.407
are applicable to plant constructed by contract or force account. This
testing standard provides for the following:
(1) Specific types of tests or measurements for the different types
of telecommunications plant and equipment;
(2) The method of measurement and types of measuring equipment;
(3) The expected results and tolerances permitted to meet the
acceptable standards and objectives;
(4) Suggested formats for recording the results of the measurements
and tests; and
(5) Some probable causes of nonconformance and methods for
corrective action, where possible.
(b) Alternative methods of measurements that provide suitable
alternative results shall be permitted with the concurrence of the
Rural Utilities Service (RUS).
(c) For the purpose of this testing standard, a ``measurement''
shall be defined as an evaluation where quantitative data is obtained
(e.g., resistance in ohms, structural return loss in decibels (dB),
etc.) and a ``test'' shall be defined as an evaluation where no
quantitative data is obtained (e.g., a check mark indicating
conformance is usually the result of the test).
(d) The sequence of tests and measurements described in this
standard have been prepared as a guide. Variations from the sequence
may be necessary on an individual application basis.
(e) There is some overlap in the methods of testing shown; also,
the extent of each phase of testing may vary on an individual basis.
The borrower shall determine the overall plan of testing, the need and
extent of testing, and the responsibility for each phase of testing.
Sec. 1755.402 Ground resistance measurements.
(a) The resistance of the central office (CO) and the remote
switching terminal (RST) ground shall be measured before and after it
has been bonded to the master ground bar (MGB) where it is connected to
the building electric service ground.
(b) The ground resistance of electronic equipment such as span line
repeaters, carrier terminal equipment, concentrators, etc. shall be
measured.
(c) Method of measurement. The connection of test equipment for the
ground resistance measurement shall be as shown in Figure 1. Refer to
RUS Bulletin 1751F-802, ``Electrical Protection Grounding
Fundamentals,'' for a comprehensive discussion of ground resistance
measurements.
(d) Test equipment. The test equipment for making this measurement
is shown in Figure 1 as follows:
BILLING CODE 3410-15-P
[[Page 23961]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.023
BILLING CODE 3410-15-C
[[Page 23962]]
(e) Applicable results. (1) For the CO and RST, the resistance
after the bond has been made to the MGB electric service ground shall
not exceed 5 ohms. Where the measured ground resistance exceeds 5 ohms,
the borrower shall determine what additional grounding, if any, shall
be provided.
(2) For electronic equipment, the ground resistance shall not
exceed 25 ohms. Where the measured ground resistance exceeds 25 ohms,
the borrower shall determine what additional grounding, if any, shall
be provided.
(3) When ground resistance measurements exceed the ground
resistance requirements of paragraphs (e)(1) and (e)(2) of this
section, refer to RUS Bulletin 1751F-802, ``Electrical Protection
Grounding Fundamentals,'' for suggested methods of reducing the ground
resistance.
(f) Data record. Results of the CO and RST ground resistance
measurements shall be recorded. A suggested format similar to Format I,
Outside Plant Acceptance Tests--Subscriber Loops, in Sec. 1755.407 or a
format specified in the applicable construction contract may be used.
Results of the electronic equipment ground resistance measurements
shall be recorded. A suggested format similar to Format II, Outside
Plant Acceptance Tests--Trunk Circuits, in Sec. 1755.407 or a format
specified in the applicable construction contract may be used. Data
showing approximate moisture content of the soil at the time of
measurement, the temperature, the type of soil and a description of the
test equipment used shall also be included.
(g) Probable causes for nonconformance. Refer to RUS Bulletin
1751F-802, ``Electrical Protection Grounding Fundamentals,'' and
Telecommunications Engineering and Construction Manual (TE&CM) Section
810, ``Electrical Protection of Electronic Analog and Digital Central
Office Equipment,'' for possible causes of nonconformance and suggested
methods for corrective action.
Sec. 1755.403 Copper cable telecommunications plant measurements.
(a) Shield or shield/armor continuity. (1) Tests and measurements
shall be made to ensure that cable shields or shield/armors are
electrically continuous. There are two areas of concern. The first is
shield or shield/armor bonding within a pedestal or splice and the
second is shield or shield/armor continuity between pedestals or
splices.
(2) Measurement techniques outlined here for verification of shield
or shield/armor continuity are applicable to buried cable plant.
Measurements of shield continuity between splices in aerial cable plant
should be made prior to completion of splicing. Conclusive results
cannot be obtained on aerial plant after all bonds have been completed
to the supporting strand, multigrounded neutral, etc.
(3) Method of measurement. (i) The shield or shield/armor
resistance measurements shall be made between pedestals or splices
using either a Wheatstone bridge or a volt-ohm meter. For loaded plant,
measurements shall be made on cable lengths that do not exceed one load
section. For nonloaded plant, measurements shall be made on cable
lengths that do not exceed 5,000 feet (ft) (1,524 meters (m)). All
bonding wires shall be removed from the bonding lugs at the far end of
the cable section to be measured. The step-by-step measurement
procedure shall be as shown in Figure 2.
(ii) Cable shield or shield/armor continuity within pedestals or
splices shall be measured with a cable shield splice continuity test
set. The step-by-step measurement procedure outlined in the
manufacturer's operating instructions for the specific test equipment
being used shall be followed.
(4) Test equipment. (i) The test equipment for measuring cable
shield or shield/armor resistance between pedestals or splices is shown
in Figure 2 as follows:
BILLING CODE 3410-15-P
[[Page 23963]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.024
BILLING CODE 3410-15-C
[[Page 23964]]
(ii) A cable shield splice continuity tester shall be used to
measure shield or shield/armor continuity within pedestals or splices.
(5) Applicable results. (i) The shield or shield/armor resistance
per 1000 ft and per kilometer (km) for cable diameters and types of
shielding materials are given in Table 1 (English Units) and Table 2
(Metric Units), respectively as follows:
Table 1.--Shield Resistance @ 68 deg.F (20 deg.C) Cable Diameters Versus Shield Types
[English Units]
----------------------------------------------------------------------------------------------------------------
Nominal resistance ohm/1000 ft.
Outside diameter inches (in.) -----------------------------------------------------------------------------
A B C D E F
----------------------------------------------------------------------------------------------------------------
0.40-0.49......................... 0.77 1.54 1.65 1.96 2.30 5.51
0.50-0.59......................... 0.64 1.28 1.37 1.63 1.91 4.58
0.60-0.69......................... 0.51 1.03 1.10 1.31 1.53 3.67
0.70-0.79......................... 0.44 0.88 0.94 ........... 1.31 3.14
0.80-0.89......................... 0.38 0.77 0.82 ........... 1.14 2.74
0.90-0.99......................... 0.35 0.69 0.74 ........... 1.03 2.47
1.00-1.09......................... 0.31 0.62 0.66 ........... 0.92 2.20
1.10-1.19......................... 0.28 0.56 0.60 ........... 0.84 2.00
1.20-1.29......................... 0.26 0.51 0.55 ........... 0.77 1.84
1.30-1.39......................... 0.24 0.48 0.51 ........... 0.71 1.70
1.40-1.49......................... 0.22 0.44 0.47 ........... 0.65 1.57
1.50-1.59......................... 0.21 0.41 0.44 ........... 0.61 1.47
1.60-1.69......................... 0.19 0.38 0.41 ........... 0.57 1.37
1.70-1.79......................... 0.18 0.37 0.39 ........... 0.54 1.30
1.80-1.89......................... 0.17 0.35 0.37 ........... 0.51 1.24
1.90-1.99......................... 0.16 0.33 0.35 ........... 0.49 1.17
2.00-2.09......................... 0.15 0.31 0.33 ........... 0.46 1.10
2.10-2.19......................... 0.15 0.29 0.31 ........... 0.43 1.03
2.20-2.29......................... 0.14 0.28 0.30 ........... 0.42 1.00
2.30-2.39......................... 0.14 0.27 0.29 ........... 0.40 0.97
2.40-2.49......................... 0.13 0.25 0.27 ........... 0.38 0.90
2.50-2.59......................... 0.12 0.24 0.26 ........... 0.36 0.87
2.60-2.69......................... 0.12 0.23 0.25 ........... 0.35 0.83
2.70-2.79......................... 0.11 0.22 0.24 ........... 0.33 0.80
2.80-2.89......................... 0.11 0.22 0.24 ........... 0.33 0.80
2.90-2.99......................... 0.11 0.22 0.23 ........... 0.32 0.77
3.00-3.09......................... 0.10 0.21 0.22 ........... 0.31 0.73
3.10-3.19......................... 0.10 0.20 0.21 ........... 0.29 0.70
3.20-3.29......................... 0.10 0.20 0.21 ........... 0.29 0.70
3.30-3.39......................... 0.09 0.19 0.20 ........... 0.28 0.67
3.40-3.49......................... 0.09 0.18 0.19 ........... 0.26 0.63
3.50-3.59......................... 0.09 0.18 0.19 ........... 0.26 0.63
3.60-3.69......................... 0.08 0.17 0.18 ........... 0.25 0.60
3.70-3.79......................... 0.08 0.17 0.18 ........... 0.25 0.60
3.80-3.89......................... 0.08 0.16 0.17 ........... 0.24 0.57
3.90-3.99......................... 0.08 0.16 0.17 ........... 0.24 0.57
4.00-4.99......................... 0.07 0.15 0.16 ........... 0.22 0.53
----------------------------------------------------------------------------------------------------------------
Where: Column A-10 mil Copper shield.
Column B--5 mil Copper shield.
Column C--8 mil Coated Aluminum and 8 mil Coated Aluminum/6 mil Coated Steel shields.
Column D--7 mil Alloy 194 shield.
Column E--6 mil Alloy 194 and 6 mil Copper Clad Stainless Steel shields.
Column F--5 mil Copper Clad Stainless Steel and 5 mil Copper Clad Alloy Steel shields.
Table 2.--Shield Resistance @ 68 deg.F (20 deg.C) Cable Diameters Versus Shield Types
[Metric Units]
----------------------------------------------------------------------------------------------------------------
Nominal Resistance ohm/km
Outside diameter millimeters (mm) -----------------------------------------------------------------------------
A B C D E F
----------------------------------------------------------------------------------------------------------------
10.2--12.5........................ 2.53 5.05 5.41 6.43 7.55 18.08
12.7--15.0........................ 2.10 4.20 4.49 5.35 6.27 15.03
15.2--17.5........................ 1.67 3.38 3.61 4.30 5.02 12.04
17.8--20.1........................ 1.44 2.89 3.08 ........... 4.30 10.30
20.3--22.6........................ 1.25 2.53 2.69 ........... 3.74 8.99
22.9--25.1........................ 1.15 2.26 2.43 ........... 3.38 8.10
25.4--27.7........................ 1.02 2.03 2.16 ........... 3.02 7.22
27.9--30.2........................ 0.92 1.84 1.97 ........... 2.76 6.56
30.5--32.8........................ 0.85 1.67 1.80 ........... 2.53 6.04
33.0--35.3........................ 0.79 1.57 1.67 ........... 2.33 5.58
35.6--37.8........................ 0.72 1.44 1.54 ........... 2.13 5.15
38.1--40.4........................ 0.69 1.34 1.44 ........... 2.00 4.82
[[Page 23965]]
40.6--42.9........................ 0.62 1.25 1.34 ........... 1.87 4.49
43.2--45.5........................ 0.59 1.21 1.28 ........... 1.77 4.26
45.7--48.0........................ 0.56 1.15 1.21 ........... 1.67 4.07
48.3--50.5........................ 0.52 1.08 1.15 ........... 1.61 3.84
50.8--53.1........................ 0.49 1.02 1.08 ........... 1.51 3.61
53.3--55.6........................ 0.49 0.95 1.02 ........... 1.41 3.38
55.9--58.2........................ 0.46 0.92 0.98 ........... 1.38 3.28
58.4--60.7........................ 0.46 0.89 0.95 ........... 1.31 3.18
61.0--63.2........................ 0.43 0.82 0.89 ........... 1.25 2.95
63.5--65.8........................ 0.39 0.79 0.85 ........... 1.18 2.85
66.0--68.3........................ 0.39 0.75 0.82 ........... 1.15 2.72
68.6--70.9........................ 0.36 0.72 0.79 ........... 1.08 2.62
71.1--73.4........................ 0.36 0.72 0.79 ........... 1.08 2.62
73.7--75.9........................ 0.36 0.72 0.75 ........... 1.05 2.53
76.2--78.5........................ 0.33 0.69 0.72 ........... 1.02 2.39
78.7--81.0........................ 0.33 0.66 0.69 ........... 0.95 2.30
81.3--83.6........................ 0.33 0.66 0.69 ........... 0.95 2.30
83.6--86.1........................ 0.29 0.62 0.66 ........... 0.92 2.20
86.4--88.6........................ 0.29 0.59 0.62 ........... 0.85 2.07
88.9--91.2........................ 0.29 0.59 0.62 ........... 0.85 2.07
91.4--93.7........................ 0.26 0.56 0.59 ........... 0.82 1.97
94.0--96.3........................ 0.26 0.56 0.59 ........... 0.82 1.97
96.5--98.8........................ 0.26 0.52 0.56 ........... 0.79 1.87
99.1--101.3....................... 0.26 0.52 0.56 ........... 0.79 1.87
101.6--103.9...................... 0.23 0.49 0.52 ........... 0.72 1.74
----------------------------------------------------------------------------------------------------------------
Where: Column A--10 mil Copper shield.
Column B--5 mil Copper shield.
Column C--8 mil Coated Aluminum and 8 mil Coated Aluminum/6 mil Coated Steel shields.
Column D--7 mil Alloy 194 shield.
Column E--6 mil Alloy 194 and 6 mil Copper Clad Stainless Steel shields.
Column F--5 mil Copper Clad Stainless Steel and 5 mil Copper Clad Alloy Steel shields.
(ii) All values of shield and shield/armor resistance provided in
Tables 1 and 2 in (a)(5)(i) of this section are considered
approximations. If the measured value corrected to 68 deg.F (20 deg.C)
is within 30 percent (%) of the value shown in Table 1 or
2, the shield and shield/armor shall be assumed to be continuous.
(iii) To correct the measured shield resistance to the reference
temperature of 68 deg.F (20 deg.C) use the following formulae:
R68=Rt/[1+A(t-68)] for English Units
R20=Rt/[1+A(t-20)] for Metric Units
Where:
R68=Shield resistance corrected to 68 deg.F in ohms.
R20=Shield resistance corrected to 20 deg.C in ohms.
Rt=Shield resistance at measurement temperature in ohms.
A=Temperature coefficient of the shield tape.
t=Measurement temperature in deg.F or ( deg.C).
(iv) The temperature coefficients (A) for the shield tapes to be
used in the formulae referenced in paragraph (a)(5)(iii) of this
section are as follows:
(A) 5 and 10 mil copper = 0.0021 for English units and 0.0039 for
Metric units;
(B) 8 mil coated aluminum and 8 mil coated aluminum/6 mil coated
steel = 0.0022 for English units and 0.0040 for Metric units;
(C) 5 mil copper clad stainless steel and 5 mil copper clad alloy
steel = 0.0024 for English units and 0.0044 for Metric units;
(D) 6 mil copper clad stainless steel = 0.0019 for English units
and 0.0035 for Metric units; and
(E) 6 and 7 mil alloy 194 = 0.0013 for English units and 0.0024 for
Metric units.
(v) When utilizing shield continuity testers to measure shield and
shield/armor continuity within pedestals or splices, refer to the
manufacturer's published information covering the specific test
equipment to be used and for anticipated results.
(6) Data record. Measurement data from shield continuity tests
shall be recorded together with anticipated Table 1 or 2 values (see
paragraph (a)(5)(i) of this section) in an appropriate format to permit
comparison. The recorded data shall include specific location, cable
size, cable type, type of shield or shield/armor, if known, etc.
(7) Probable causes for nonconformance. Among probable causes for
nonconformance are broken or damaged shields or shield/armors, bad
bonding harnesses, poorly connected bonding clamps, loose bonding lugs,
etc.
(b) Conductor continuity. After placement of all cable and wire
plant has been completed and joined together in continuous lengths,
tests shall be made to ascertain that all pairs are free from grounds,
shorts, crosses, and opens, except for those pairs indicated as being
defective by the cable manufacturer. The tests for grounds, shorts,
crosses, and opens are not separate tests, but are inherent in other
acceptance tests discussed in this section. The test for grounds,
shorts, and crosses is inherent when conductor insulation resistance
measurements are conducted per paragraph (c) of this section, while
tests for opens are inherent when tests are conducted for loop
resistance, insertion loss, noise, or return loss measurements, per
paragraphs (d), (e), or (f) of this section. The borrower shall make
certain that all defective pairs are corrected, except
[[Page 23966]]
those noted as defective by the cable manufacturer in accordance with
the marking provisions of the applicable cable and wire specifications.
All defective pairs that are not corrected shall be reported in writing
with details of the corrective measures attempted.
(c) Dc insulation resistance (IR) measurement. (1) IR measurements
shall be made on completed lengths of insulated cable and wire plant.
(2) Method of measurement. (i) The IR measurement shall be made
between each conductor and all other conductors, sheath, shield and/or
shield/armor, and/or support wire electrically connected together and
to the main distributing frame (MDF) ground. The measurement shall be
made from the central office with the entire length of the cable under
test and, where used with all protectors and load coils connected. For
COs containing solid state arresters, the solid state arresters shall
be removed before making the IR measurements. Field mounted voice
frequency repeaters, where used, may be left connected for the IR test
but all carrier frequency equipment, including carrier repeaters and
terminals, shall be disconnected. Pairs used to feed power remote from
the CO shall have the power disconnected and the tip and ring
conductors shall be opened before making IR tests. All conductors shall
be opened at the far end of the cable being measured.
(ii) IR tests are normally made from the MDF with all CO equipment
disconnected at the MDF, but this test may be made on new cables at
field locations before they are spliced to existing cables. The method
of measurement shall be as shown in Figure 3 as follows:
BILLING CODE 3410-15-P
[[Page 23967]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.025
BILLING CODE 3410-15-C
[[Page 23968]]
(iii) If the IR of the conductor cannot be measured because of
breakdown of lightning arresters by the test voltage, the arrester
units shall be removed and the conductor IR retested. If the IR then
meets the minimum requirements, the conductor will be considered
satisfactory. Immediately following the IR tests, all arrester units
which have been removed shall be reinstalled.
(3) Test equipment. (i) IR measurements shall be made with either
an insulation resistance test set or a direct current (dc) bridge type
megohmmeter.
(ii) The IR test set shall have an output voltage not to exceed 500
volts dc and shall be of the hand cranked or battery operated type.
(iii) The dc bridge type megohmmeter, which may be alternating
current (ac) powered, shall have scales and multiplier which make it
possible to accurately read IR from 1 megohm to 1 gigohm. The voltage
applied to the conductors under test shall not exceed ``250 volts dc''
when using an instrument having adjustable test voltage levels. This
will help to prevent breakdown of lightning arresters.
(4) Applicable results. (i) For all new insulated cable or wire
facilities, the expected IR levels are normally greater than 1,000 to
2,000 megohm-mile (1,609 to 3,218 megohm-km). A value of 500 megohm-
mile (805 megohm-km) at 68 deg.F (20 deg.C) shall be the minimum
acceptable value of IR. IR varies inversely with the length and the
temperature.
(ii) The megohm-mile (megohm-km) value for a conductor may be
computed by multiplying the actual scale reading in megohms on the test
set by the length in miles (km) of the conductor under test.
(iii) The objective insulation resistance may be determined by
dividing 500 by the length in miles (805 by the length in km) of the
cable or wire conductor being tested. The resulting value shall be the
minimum acceptable meter scale reading in megohms.
(iv) Due to the differences between various insulating materials
and filling compounds used in manufacturing cable or wire, it is
impractical to provide simple factors to predict the magnitude of
variation in insulation resistance due to temperature. The variation
can, however, be substantial for wide excursions in temperature from
the ambient temperature of 68 deg.F (20 deg.C).
(v) Borrowers should be certain that tip and ring IR measurements
of each pair are approximately the same. Borrowers should also be
certain that IR measurements are similar for cable or wire sections of
similar length and cable or wire type. If some pairs measure
significantly lower, borrowers should attempt to improve these pairs in
accordance with cable manufacturer's recommendations.
Note: Only the megohm-mile (megohm-km) requirement shall be
cause for rejection, not individual measurement differences.
(5) Data record. The measurement data shall be recorded. Suggested
formats similar to Format I, Outside Plant Acceptance Tests--Subscriber
Loops, or Format II, Outside Plant Acceptance Tests--Trunk Circuits, in
Sec. 1755.407 or formats specified in the applicable construction
contract may be used.
(6) Probable causes for nonconformance. (i) When an IR measurement
is below 500 megohm-mile (805 megohm-km), the cable or wire temperature
at the time of testing must then be taken into consideration. If this
temperature is well above 68 deg.F (20 deg.C), the measurement shall
be disregarded and the cable or wire shall be remeasured at a time when
the temperature is approximately 68 deg.F (20 deg.C). If the result
is then 500 megohm-mile (805 megohm-km) or greater, the cable or wire
shall be considered satisfactory.
(ii) Should the cable or wire fail to meet the 500 megohm-mile (805
megohm-km) requirement when the temperature is known to be
approximately 68 deg.F (20 deg.C) there is not yet justification for
rejection of the cable or wire. Protectors, lightning arresters, etc.,
may be a source of low insulation resistance. These devices shall be
removed from the cable or wire and the cable or wire IR measurement
shall be repeated. If the result is acceptable, the cable or wire shall
be considered acceptable. The removed devices which caused the low
insulation resistance value shall be identified and replaced, if found
defective.
(iii) When the cable or wire alone is still found to be below the
500 megohm-mile (805 megohm-km) requirement after completing the steps
in paragraph (c)(6)(i) and/or paragraph (c)(6)(ii) of this section, the
test shall be repeated to measure the cable or wire in sections to
isolate the piece(s) of cable or wire responsible. The cable or wire
section(s) that is found to be below the 500 megohm-mile (805 megohm-
km) requirement shall be either repaired in accordance with the cable
or wire manufacturer's recommended procedure or shall be replaced as
directed by the borrower.
(d) Dc loop resistance and dc resistance unbalance measurement. (1)
When specified by the borrower, dc loop resistance and dc resistance
unbalance measurements shall be made on all cable pairs used as trunk
circuits. The dc loop resistance and dc resistance unbalance
measurements shall be made between CO locations. Measurements shall
include all components of the cable path.
(2) Dc loop resistance and dc resistance unbalance measurements
shall be made on all cable pairs used as subscriber loop circuits when:
(i) Specified by the borrower;
(ii) A large number of long loops terminate at one location
(similar to trunk circuits); or
(iii) Circuit balance is less than 60 dB when computed from noise
measurements as described in paragraph (e) of this section.
(3) Dc resistance unbalance is controlled to the maximum possible
degree by the cable specification. Allowable random unbalance is
specified between tip and ring conductors within each reel. Further
random patterns should occur when the cable conductor size changes.
Cable meeting the unbalance requirements of the cable specification may
under some conditions result in unacceptable noise levels as discussed
in paragraph (d)(6)(iii) of this section.
(4) Method of measurement. The method of measurement shall be as
detailed in Figures 4 and 5.
(5) Test equipment. The test equipment is shown in Figures 4 and 5
as follows:
BILLING CODE 3410-15-P
[[Page 23969]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.026
[[Page 23970]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.027
BILLING CODE 3410-15-C
[[Page 23971]]
(6) Applicable results. (i) The measured dc loop resistance shall
be within 5% of the calculated dc loop resistance when
corrected for temperature.
(ii) The calculated dc loop resistance is computed as follows:
(A) Multiply the length of each different gauge by the applicable
resistance per unit length as shown in Table 3 as follows:
Table 3.--DC Loop Resistance @ 68 deg.F (20 deg.C)
------------------------------------------------------------------------
Loop resistance
American wire gauge (AWG) -------------------------------
ohms/1000 ft ohms/km
------------------------------------------------------------------------
19...................................... 16.1 52.8
22...................................... 32.4 106.3
24...................................... 51.9 170.3
26...................................... 83.3 273.3
------------------------------------------------------------------------
(B) Add the individual resistances for each gauge to give the total
calculated dc loop resistance at a temperature of 68 deg.F (20 deg.C).
(C) Correct the total calculated dc loop resistance at the
temperature of 68 deg.F (20 deg.C) to the measurement temperature by
the following formulae:
Rt=R68 x [1+0.0022 x t--68)] for English Units
Rt=R20 x [1+0.0040 x (t--20)] for Metric Units
Where:
Rt = Loop resistance at the measurement temperature in ohms.
R68 = Loop resistance at a temperature of 68 deg.F in ohms.
R20 = Loop resistance at a temperature of 20 deg.C in ohms.
t = Measurement temperature in deg.F or ( deg.C).
(D) Compare the calculated dc loop resistance at the measurement
temperature to the measured dc loop resistance to determine compliance
with the requirement specified in paragraph (d)(6)(i) of this section.
(iii) Resistance varies directly with temperature change. For
copper conductor cables, the dc resistance changes by 1%
for every 5 deg.F (2.8 deg.C) change in temperature from
68 deg.F (20 deg.C).
(iv) The dc resistance unbalance between the individual conductors
of a pair shall not exceed that value which will result in a circuit
balance of less than 60 dB when computed from noise measurements as
described in paragraph (e) of this section. It is impractical to
establish a precise limit for overall circuit dc resistance unbalance
due to the factors controlling its contribution to circuit noise. These
factors include location of the resistance unbalance in relation to a
low impedance path to ground (close to the central office) and the
magnitude of unbalance in short lengths of cable making up the total
circuit length. The objective is to obtain the minimum unbalance
throughout the entire circuit when it is ascertained through noise
measurements that dc resistance unbalance may be contributing to poor
cable balance.
(v) Pairs with poor noise balance may be improved by reversing tip
and ring conductors of pairs at cable splices. Where dc resistance
unbalances are systematic over the total trunk circuit or loop circuit
length, tip and ring reversals may be made at frequent intervals. Where
the unbalances are concentrated in a shorter section of cable, only one
tip and ring reversal should be required. Concentrated dc resistance
unbalance produces maximum circuit noise when located adjacent to the
central office. Concentrated dc resistance unbalance will contribute to
overall circuit noise at a point approximately two-thirds (\2/3\) of
the distance to the subscriber. All deliberate tip and ring reversals
shall be tagged and identified to prevent plant personnel from removing
the reversals when resplicing these connections in the future. The
number of tip and ring reversals shall be held to a minimum.
(vi) A systematic dc resistance unbalance can sometimes be
accompanied by other cable parameters that are marginal. Among these
are pair-to-pair capacitance unbalance, capacitance unbalance-to-
ground, and 150 kilohertz (kHz) crosstalk loss. Engineering judgment
has to be applied in each case. Rejection of cable for excessive dc
resistance unbalance shall only apply to a single reel length, or
shorter.
[[Page 23972]]
(7) Data record. The measurement data for dc loop resistance and dc
resistance unbalance shall be recorded. Suggested formats similar to
Format I for subscriber loops and Format II for trunk circuits in
Sec. 1755.407 or formats specified in the applicable construction
contract may be used.
(8) Probable causes for nonconformance. Dc loop resistance and dc
resistance unbalance are usually the result of the resistance of
individual conductors used in the manufacture of the cable. Resistance
unbalance can be worsened by defective splicing of the conductors
(splicing connectors, improper crimping tool, etc.).
(e) Subscriber loop measurement (loop checking). (1) When specified
by the borrower, insertion loss and noise measurements shall be
performed on subscriber loops after connection of a line circuit to the
loop by the one person method using loop checking equipment from the
customer access location. For this method, the central office should be
equipped with a 900 ohm plus two microfarad quiet termination and a
milliwatt generator having the required test frequencies; or a portable
milliwatt generator having the desired frequencies may be used,
especially, where several small offices are involved.
(2) At a minimum, insertion loss and frequency response of
subscriber loop plant shall be measured at 1,000, 1,700, 2,300, and
2,800 Hertz (Hz). When additional testing frequencies are desired, the
additional frequencies shall be specified in the applicable
construction contract.
(3) Measurements of insertion loss and noise shall be made on five
percent or more of the pairs. A minimum of five pairs shall be tested
on each route. Pairs shall be selected on a random basis with greater
consideration in the selection given to the longer loops. Consideration
shall be given to measuring a large percentage, up to 100 percent, of
all loops.
(4) Method of measurement--(i) Insertion loss. The step-by-step
measurement procedure shall be as shown in Figure 6. The output level
of the milliwatt generator tones shall be determined prior to leaving
the CO. This shall be accomplished by dialing the milliwatt generator
number from a spare line at the MDF and measuring with the same
equipment to be used in the tests at customer access locations. The
output levels shall be recorded for reference later. Insertion loss
measurements shall be made across the tip and ring terminals of the
pair under test. Figure 6 is as follows:
BILLING CODE 3410-15-P
[[Page 23973]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.028
BILLING CODE 3410-15-C
[[Page 23974]]
(ii) Noise. The step-by-step measurement procedure shall be as
shown in Figure 7. Prior to leaving the CO for testing, dial the 900
ohm plus two microfarad quiet termination from a spare pair and measure
the termination to determine that it actually is quiet. Circuit noise
(noise-metallic) shall be measured at the customer access location
across the tip and ring terminals of the pair under test. Power
influence (direct reading with loop checking equipment) shall be
measured at the customer access location from tip and ring conductors-
to-ground (this connection is completed via the test unit). The power
influence measurement includes the entire talking connection from the
quiet termination to the customer. (That is, the power influence
measurement includes all the CO equipment which normally makes up the
connection.) Figure 7 is as follows:
BILLING CODE 3410-15-P
[[Page 23975]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.029
BILLING CODE 3410-15-C
[[Page 23976]]
(5) Test equipment. (i) Loop checking equipment which is available
from several manufacturers may be used for these measurements. The
equipment should have the capability of measuring loop current,
insertion loss, circuit noise (NM) and power influence (PI). The test
equipment manufacturer's operating instructions shall be followed.
(ii) There should be no measurable transmission loss when testing
through loop extenders.
(6) Applicable results--(i) Insertion loss. (A) For D66 loaded
cables (a specific loading scheme using a 66 millihenry inductor spaced
nominally at 4,500 ft [1,371 m] intervals) measured at a point one-half
section length beyond the last load point, the measured nonrepeated
insertion loss shall be within 10% at 1000, 1700, 2300,
and 2800 Hz, 15% at 3400 Hz and 20% at 4000
Hz of the calculated insertion loss at the same frequencies and
temperature.
(B) For H88 loaded cables (a specific loading scheme using an 88
millihenry inductor spaced nominally at 6,000 ft [1,829 m] intervals)
measured at a point one-half section length beyond the last load point,
the measured nonrepeatered insertion loss shall be within
10% at 1000, 1700, and 2300 Hz, 15% at 2800 Hz, and
20% at 3400 Hz of the calculated insertion loss at the
same frequencies and temperature.
(C) For nonloaded cables, the measured insertion loss shall be
within 10% at 1000, 1700, 2300, and 2800 Hz,
15% at 3400 Hz and 20% at 4000 Hz of the calculated
insertion loss at the same frequencies and temperature.
(D) For loaded cables, the calculated loss at each desired
frequency shall be computed as follows:
(1) Multiply the length in miles (km) of each different gauge in
the loaded portion of the loop (between the office and a point one-half
load section beyond the furthest load point) by the applicable decibel
(dB)/mile (dB/km) value shown in Table 4 or 5. This loss represents the
total loss for each gauge in the loaded portion of the loop;
(2) Multiply the length in miles (km) of each different gauge in
the end section or nonloaded portion of the cable (beyond a point one-
half load section beyond the furthest load point) by the applicable dB/
mile (dB/km) value shown in Table 6. This loss represents the total
loss for each gauge in the nonloaded portion of the loop; and
(3) The total calculated insertion loss is computed by adding the
individual losses determined in paragraphs (e)(6)(i)(D)(1) and
(e)(6)(i)(D)(2) of this section.
(E) For nonloaded cables, the calculated loss at each desired
frequency shall be computed by multiplying the length in miles (km) of
each different gauge by the applicable dB/mile (dB/km) value shown in
Table 6 and then adding the individual losses for each gauge to
determine the total calculated insertion loss for the nonloaded loop.
(F) The attenuation information in Tables 4, 5, and 6 are based on
a cable temperature of 68 deg.F (20 deg.C). Insertion loss varies
directly with temperature. To convert measured losses for loaded cables
to a different temperature, use the following value for copper
conductors: For each 5 deg.F ( 2.8 deg.C)
change in the temperature from 68 deg.F (20 deg.C), change the
insertion loss at any frequency by 1%. To convert measured
losses for nonloaded cables to a different temperature, use the
following value for copper conductors: For each 10 deg.F
(5.6 deg.C) change in the temperature from 68 deg.F (20
deg.C), change the insertion loss at any frequency by 1%.
Tables 4, 5, and 6 are as follows:
Table 4.--Frequency Attenuation @ 68 deg.F (20 deg.C) D66 Loaded Exchange Cables 83 nanofarad (nF)/mile (52 nF/
km) (See Note)
----------------------------------------------------------------------------------------------------------------
Attenuation dB/mile (dB/km) AWG
Frequency (Hz) -------------------------------------------------------------------
19 22 24 26
----------------------------------------------------------------------------------------------------------------
200......................................... 0.41 (0.26) 0.67 (0.42) 0.90 (0.56) 1.21 (0.75)
400......................................... 0.43 (0.26) 0.77 (0.48) 1.09 (0.68) 1.53 (0.95)
600......................................... 0.44 (0.27) 0.80 (0.49) 1.17 (0.73) 1.70 (1.06)
800......................................... 0.44 (0.27) 0.81 (0.50) 1.21 (0.75) 1.80 (1.12)
1000........................................ 0.44 (0.27) 0.82 (0.51) 1.23 (0.76) 1.86 (1.15)
1200........................................ 0.45 (0.28) 0.83 (0.52) 1.24 (0.77) 1.91 (1.19)
1400........................................ 0.45 (0.28) 0.83 (0.52) 1.26 (0.78) 1.94 (1.20)
1600........................................ 0.45 (0.28) 0.84 (0.52) 1.26 (0.78) 1.96 (1.22)
1800........................................ 0.45 (0.28) 0.84 (0.52) 1.27 (0.78) 1.98 (1.23)
2000........................................ 0.46 (0.29) 0.85 (0.53) 1.28 (0.79) 1.99 (1.24)
2200........................................ 0.46 (0.29) 0.85 (0.53) 1.29 (0.80) 2.01 (1.25)
2400........................................ 0.47 (0.29) 0.86 (0.53) 1.30 (0.81) 2.02 (1.26)
2600........................................ 0.47 (0.29) 0.87 (0.54) 1.31 (0.81) 2.04 (1.27)
2800........................................ 0.48 (0.30) 0.88 (0.55) 1.32 (0.82) 2.07 (1.29)
3000........................................ 0.49 (0.30) 0.89 (0.55) 1.34 (0.83) 2.10 (1.30)
3200........................................ 0.50 (0.31) 0.91 (0.57) 1.36 (0.84) 2.13 (1.32)
3400........................................ 0.52 (0.32) 0.93 (0.58) 1.40 (0.87) 2.19 (1.36)
3600........................................ 0.54 (0.34) 0.97 (0.60) 1.45 (0.90) 2.26 (1.40)
3800........................................ 0.57 (0.35) 1.02 (0.63) 1.52 (0.94) 2.36 (1.47)
4000........................................ 0.62 (0.38) 1.10 (0.68) 1.63 (1.01) 2.53 (1.57)
----------------------------------------------------------------------------------------------------------------
Note: Between end-section lengths of 2,250 ft (686 m) for D66 loading.
Table 5.--Frequency Attenuation @ 68 deg.F (20 deg.C) H88 Loaded Exchange Cables 83 nF/ mile (52 nF/km) (See
Note)
----------------------------------------------------------------------------------------------------------------
Attenuation dB/mile (dB/km) AWG
Frequency (Hz) -------------------------------------------------------------------
19 22 24 26
----------------------------------------------------------------------------------------------------------------
200......................................... 0.40 (0.25) 0.66 (0.41) 0.90 (0.56) 1.20 (0.75)
[[Page 23977]]
400......................................... 0.42 (0.26) 0.76 (0.47) 1.08 (0.67) 1.53 (0.95)
600......................................... 0.43 (0.27) 0.79 (0.49) 1.16 (0.72) 1.70 (1.06)
800......................................... 0.43 (0.27) 0.80 (0.50) 1.20 (0.75) 1.80 (1.12)
1000........................................ 0.43 (0.27) 0.81 (0.50) 1.23 (0.76) 1.86 (1.15)
1200........................................ 0.44 (0.27) 0.82 (0.51) 1.24 (0.77) 1.91 (1.19)
1400........................................ 0.44 (0.28) 0.82 (0.51) 1.25 (0.78) 1.94 (1.20)
1600........................................ 0.44 (0.27) 0.83 (0.52) 1.26 (0.78) 1.97 (1.22)
1800........................................ 0.45 (0.28) 0.84 (0.52) 1.28 (0.79) 1.99 (1.24)
2000........................................ 0.46 (0.29) 0.85 (0.53) 1.29 (0.80) 2.02 (1.26)
2200........................................ 0.47 (0.29) 0.86 (0.53) 1.31 (0.81) 2.06 (1.28)
2400........................................ 0.48 (0.30) 0.89 (0.55) 1.34 (0.83) 2.10 (1.30)
2600........................................ 0.50 (0.31) 0.92 (0.57) 1.39 (0.86) 2.18 (1.35)
2800........................................ 0.53 (0.33) 0.97 (0.60) 1.47 (0.91) 2.29 (1.42)
3000........................................ 0.59 (0.37) 1.07 (0.66) 1.60 (0.99) 2.48 (1.54)
3200........................................ 0.71 (0.44) 1.26 (0.78) 1.87 (1.16) 2.86 (1.78)
3400........................................ 1.14 (0.71) 1.91 (1.19) 2.64 (1.64) 3.71 (2.30)
3600........................................ 4.07 (2.53) 4.31 (2.68) 4.65 (2.90) 5.30 (3.29)
3800........................................ 6.49 (4.03) 6.57 (4.08) 6.72 (4.18) 7.06 (4.39)
4000........................................ 8.22 (5.11) 8.27 (5.14) 8.36 (5.19) 8.58 (5.33)
----------------------------------------------------------------------------------------------------------------
Note: Between end-section lengths of 3,000 ft (914 m) for H88 loading.
Table 6.--Frequency Attenuation @ 68 deg.F (20 deg.C) Nonloaded Exchange Cables 83 nF/ mile (52 nF/km) AWG
----------------------------------------------------------------------------------------------------------------
Attenuation dB/mile (dB/km) AWG
Frequency (Hz) -------------------------------------------------------------------
19 22 24 26
----------------------------------------------------------------------------------------------------------------
200......................................... 0.58 (0.36) 0.82 (0.51) 1.03 (0.64) 1.30 (0.81)
400......................................... 0.81 (0.51) 1.15 (0.71) 1.45 (0.90) 1.84 (1.14)
600......................................... 0.98 (0.61) 1.41 (0.87) 1.77 (1.10) 2.26 (1.40)
800......................................... 1.13 (0.70) 1.62 (1.01) 2.04 (1.27) 2.60 (1.61)
1000........................................ 1.25 (0.78) 1.80 (1.12) 2.28 (1.42) 2.90 (1.80)
1200........................................ 1.36 (0.84) 1.97 (1.22) 2.50 (1.55) 3.17 (1.97)
1400........................................ 1.46 (0.91) 2.12 (1.32) 2.69 (1.67) 3.42 (2.12)
1600........................................ 1.55 (0.96) 2.26 (1.40) 2.87 (1.78) 3.65 (2.27)
1800........................................ 1.63 (1.01) 2.39 (1.48) 3.04 (1.89) 3.87 (2.40)
2000........................................ 1.71 (1.06) 2.51 (1.56) 3.20 (1.99) 4.08 (2.53)
2200........................................ 1.78 (1.11) 2.62 (1.63) 3.35 (2.08) 4.27 (2.65)
2400........................................ 1.85 (1.15) 2.73 (1.70) 3.49 (2.17) 4.45 (2.76)
2600........................................ 1.91 (1.19) 2.83 (1.76) 3.62 (2.25) 4.63 (2.88)
2800........................................ 1.97 (1.22) 2.93 (1.82) 3.75 (2.33) 4.80 (2.98)
3000........................................ 2.03 (1.26) 3.02 (1.88) 3.88 (2.41) 4.96 (3.08)
3200........................................ 2.08 (1.29) 3.11 (1.93) 4.00 (2.48) 5.12 (3.18)
3400........................................ 2.13 (1.32) 3.19 (1.98) 4.11 (2.55) 5.27 (3.27)
3600........................................ 2.18 (1.35) 3.28 (2.04) 4.22 (2.62) 5.41 (3.36)
3800........................................ 2.22 (1.38) 3.36 (2.09) 4.33 (2.69) 5.55 (3.45)
4000........................................ 2.27 (1.41) 3.43 (2.13) 4.43 (2.75) 5.69 (3.53)
----------------------------------------------------------------------------------------------------------------
(G) For loaded subscriber loops, the 1 kHz loss shall be
approximately 0.45 dB per 100 ohms of measured dc loop resistance. This
loss shall be the measured loss less the net gain of any voice
frequency repeaters in the circuit. Testing shall also be conducted to
verify that the loss increases gradually as the frequency increases.
The loss on H88 loaded loops should be down only slightly at 2.8 kHz
but drop rapidly above 2.8 kHz. The loss on D66 loaded loops shall be
fairly constant to about 3.4 kHz and there shall be good response at
4.0 kHz. When voice frequency repeaters are in the circuit there will
be some frequency weighting in the build-out network and the loss at
the higher frequencies will be greater than for nonrepeatered loops.
(H) For nonloaded subscriber loops, the 1 kHz loss shall be
approximately 0.9 dB per 100 ohms of measured dc loop resistance.
Testing shall also be conducted to verify that the loss is
approximately a straight line function with no abrupt changes. The 3
kHz loss should be approximately 70% higher than the 1 kHz loss.
(ii) Noise. The principal objective related to circuit noise
(noise-metallic) and the acceptance of new plant is that circuit noise
levels be 20 dBrnc or less (decibels above reference noise, C-message
weighted (a weighting derived from listening tests, to indicate the
relative annoyance or speech impairment by an interfering signal of
frequency (f) as heard through a ``500-type'' telephone set)). For most
new, properly installed, plant construction, circuit noise will usually
be considerably less than 20 dBrnc unless there are unusually long
sections of telephone plant in parallel with electric power facilities
and/or power influence of paralleling electric facilities is abnormally
high. When circuit noise is
[[Page 23978]]
20 dBrnc or less, the loop plant shall be considered acceptable. When
measured circuit noise is greater than 20 dBrnc, loop plant shall still
be considered acceptable providing circuit balance (power influence
reading minus circuit noise readings) is 60 dB or greater and power
influence readings are 85 dBrnc or greater. When circuit noise is
greater than 20 dBrnc and circuit balance is less than 60 dB and/or
power influence is less than 85 dBrnc, loop plant shall not be
considered acceptable and the loop plant shall be remedied to make
circuit balance equal to or greater than 60 dB.
(7) Data record. Measurement data shall be recorded. A suggested
format similar to Format I for subscriber loops in Sec. 1755.407 or a
format specified in the applicable construction contract may be used.
(8) Probable causes for nonconformance.--(i) Insertion loss. Some
of the more common causes for failing to obtain the desired results may
be due to reversed load coil windings, missing load coils, bridge taps
between load coils, load coil spacing irregularities, excessive end
sections, cables having high or low mutual capacitance, load coils
having the wrong inductance, load coils inadvertently installed in
nonloaded loops, moisture or water in cable, split pairs, and
improperly spliced connections. The above factors can occur singularly
or in combination. Experience to date indicates that the most common
problems are missing load coils, reversed load coil windings or bridge
taps.
(ii) Noise. Some of the common causes for failing to obtain the
desired results may be due to high power influence from paralleling
electrical power systems, poor telephone circuit balance, discontinuous
cable shields, inadequate bonding and grounding of cable shields, high
capacitance unbalance-to-ground of the cable pairs, high dc loop
resistance unbalance, dc loop current less than 20 milliamperes, etc.
The above factors can occur singularly or in combination. See TE&CM
Section 451, Telephone Noise Measurement and Mitigation, for steps to
be taken in reducing telecommunications line noise.
(f) One-person open circuit measurement (subscriber loops). (1)
When specified by the borrower, open circuit measurements shall be made
on all loaded and nonloaded subscriber loops upon completion of the
cable work to verify that the plant is free from major impedance
irregularities.
(2) For loaded loops, open circuit measurements shall be made using
one of the following methods:
(i) Impedance or pulse return pattern, with cable pair trace
compared to that of an artificial line of the same length and gauge.
For best results, a level tracer or fault locator with dual trace
capability is required;
(ii) Return loss using a level tracer, with cable pair compared to
an artificial line of the same length and gauge connected in lieu of a
Precision Balance Network (PBN). This method can be made with level
tracers having only single trace capability; or
(iii) Open circuit structural return loss using a level tracer.
This method can be made with level tracer having only single trace
capability.
(3) Of the three methods suggested for loaded loops, the method
specified in paragraph (f)(2)(ii) of this section is the preferred
method because it can yield both qualitative and quantitative results.
The methods specified in paragraphs (f)(2)(i) and (f)(2)(iii) of this
section can be used as trouble shooting tools should irregularities be
found during testing.
(4) For nonloaded loops, open circuit measurements shall be made
using the method specified in paragraph (f)(2)(i) of this section.
(5) Method of measurement. Open circuit measurements shall be made
at the CO on each loaded and nonloaded pair across the tip and ring
terminals of the pair under test. All CO equipment shall be
disconnected at the MDF for this test. For loaded loops containing
voice frequency repeaters installed in the CO or field mounted, the
open circuit measurement shall be made after the repeaters have been
disconnected. Where field mounted repeaters are used, the open circuit
measurement shall be made at the repeater location in both directions.
(i) Impedance or pulse return pattern. The step-by-step measurement
procedure using the impedance or pulse return pattern for loaded and
nonloaded loops shall be as shown in Figure 8. An artificial line of
the same makeup as the cable to be tested shall be set up. The traces
of the impedance or pulse return pattern from the cable pair and the
artificial line shall be compared and should be essentially identical.
If the impedance or pulse return traces from the cable pair are
different than the artificial line trace, cable faults are possible.
When the cable pair trace indicates possible defects, the defects
should be identified and located. One method of identifying and
locating defects involves introducing faults into the artificial line
until its trace is identical with the cable trace.
(ii) Return loss balanced to artificial line. The step-by-step
measurement procedure using the return loss balanced to artificial line
for loaded loops shall be as shown in Figure 9. An artificial line of
the same makeup as the cable to be tested shall be set up. The
artificial line is connected to the external network terminals of the
test set. The cable pair under test is compared to this standard. When
defects are found, they should be identified and located by introducing
faults into the artificial line. This is more difficult than with the
method referenced in paragraph (f)(5)(i) of this section since this
measurement is more sensitive to minor faults and only a single trace
is used.
(iii) Open circuit structural return loss using level tracer. The
step-by-step measurement procedure using the level tracer for loaded
loops shall be as shown in Figure 10. The cable pair is compared to a
PBN.
(6) Test equipment. Equipment for performing these tests is shown
in Figures 8 through 10. For loaded loops, artificial loaded lines must
be of the same gauge and loading scheme as the line under test. For
nonloaded loops, artificial nonloaded lines must be of the same gauge
as the line under test. Artificial lines should be arranged using
switches or other quick connect arrangements to speed testing and
troubleshooting. Figures 8 through 10 are as follows:
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[[Page 23982]]
(7) Applicable results. (i) For loaded and nonloaded loops, the two
traces in the pulse return pattern or impedance method (paragraph
(f)(5)(i) of this section) shall be essentially identical. The degree
of comparison required of the two traces is to be determined by
experience.
(ii) For loaded loops, results for return loss measurements using a
level tracer, with artificial line, in lieu of a PBN (paragraph
(f)(5)(ii) of this section) shall meet the following requirements:
(A) For D66 and H88 loaded cables the structural return loss (SRL)
values shall range between 28 and 39 dB, respectively, at the critical
frequency of structural return loss (CFSRL) within the pass band of the
loading system being used. The minimum SRL value for uniform gauge
shall be 25 dB CFSRL. These SRL values apply for loaded cables of
uniform gauge for the entire length of the subscriber loop circuit.
Subscriber loop circuits shall meet the loading spacing deviations and
the cable mutual capacitance requirements in the applicable RUS cable
specifications;
(B) For mixed gauge loaded cables the SRL values shall be 25 and 27
dB CFSRL, respectively, and the minimum SRL value shall be 22 dB CFSRL;
and
(C) The two traces in the pulse return pattern should be
essentially identical. The degree of comparison required of the two
traces is determined by experience.
(iii) For loaded loops, the results of open circuit structural
return loss measurements using a level tracer (paragraph (f)(5)(iii) of
this section) shall meet the following requirements. For D66 and H88
loaded cables with uniform or mixed gauges, the worst value allowed for
measured open circuit structural return loss between 1,000-3,500 Hz and
1,000-3,000 Hz, respectively, shall be approximately 0.9 dB (round
trip) for each 100 ohms outside plant dc loop resistance including the
resistance of the load coils. The value of 0.9 dB per 100 ohms for the
round trip loss remains reasonably accurate as long as:
(A) The subscriber end section of the loaded pair under test is
approximately 2,250 ft (685 m) for D66 loading or 3,000 ft (914 m) for
H88 loading in length; and
(B) The one-way 1,000 Hz loss does not exceed 10 dB.
(iv) For loaded loops, the measured value of open circuit
structural return loss can only be as accurate as the degree to which
the dc loop resistance of the loaded pair under test is known. Most
accurate results shall be obtained when the dc loop resistance is known
by actual measurements as described in paragraph (d) of this section.
Furthermore, where the dc loop resistance is measured at the same time
as the open circuit structural return loss, no correction for
temperature is needed because the loss is directly proportional to the
loop resistance. Where it is not practical to measure the dc loop
resistance, it shall be calculated and corrected for temperature as
specified in paragraph (d)(6)(ii) of this section. When measuring
existing plant, care shall be taken to verify the accuracy of the
records, if they are used for the calculation of the dc loop
resistance. For buried plant, the temperature correction shall be based
at the normal depth of the cable in the ground. (Temperature can be
measured by boring a hole to cable depth with a ground rod, placing a
thermometer in the ground at the cable depth, and taking and averaging
several readings during the course of the resistance measurements.) For
aerial cable it shall be based on the temperature inside the cable
sheath.
(v) For loaded loops, the best correlation between the measured and
the expected results shall be obtained when the cable is of one gauge,
one size, and the far end section is approximately 2,250 ft (685 m) for
D66 loading or 3,000 ft (914 m) for H88 loading. Mixing gauges and
cable sizes will result in undesirable small reflections whose
frequency characteristics and magnitude cannot be accurately predicted.
In subscriber loop applications, cable gauge may be somewhat uniform
but the cable pair size most likely will not be uniform as cable pair
sizes taper off toward the customer access location and a downward
adjustment of 1 dB of the allowed value shall be acceptable. ``Long''
end sections (as defined in TE&CM Section 424, ``Guideline for
Telecommunications Subscriber Loop Plant'') lower the expected value, a
further downward adjustment of 3 dB in the allowed value shall be
acceptable.
[[Page 23983]]
(vi) For loaded loops, the limiting factor when making open circuit
structural return loss measurements is when the 1,000 Hz one-way loss
of the loaded cable pair under test becomes 10 dB or greater; it
becomes difficult to detect the presence of irregularities beyond the
10 dB point on the loop. To overcome this difficulty, loaded loops
having a one-way loss at 1,000 Hz greater than 10 dB shall be opened at
some convenient point (such as a pedestal or ready access enclosure)
and loss measurements at the individual portions measuring less than 10
dB one-way shall be made separately. When field mounted voice frequency
repeaters are used, the measurement shall be made at the repeater
location in both directions.
(8) Data record. (i) When performing a pulse return pattern or
impedance open circuit measurement on loaded and nonloaded loops, a
``check mark'' indicating that the pair tests good or an ``X''
indicating that the pair does not test good shall be recorded in the
SRL column. A suggested format similar to Format I for subscriber loops
in Sec. 1755.407 or a format specified in the applicable construction
contract may be used.
(ii) When performing open circuit return loss measurements using
the return loss balanced to an artificial line or return loss using a
level tracer on loaded loops, the value of the poorest (lowest
numerical value) SRL and its frequency in the proper column between
1,000 and 3,500 Hz for D66 loading or between 1,000 and 3,000 Hz for
H88 loading shall be recorded. A suggested format similar to Format I
for subscriber loops in Sec. 1755.407 or a format specified in the
applicable construction contract may be used.
(9) Probable causes for nonconformance. Some of the more common
causes for failing to obtain the desired results may be due to reversed
load coil windings, missing load coils, bridge taps between load coils,
load coil spacing irregularities, excessive end sections, cables having
high or low mutual capacitance, load coils inadvertently installed in
nonloaded loops, moisture or water in the cable, load coils having the
wrong inductance, split pairs, and improperly spliced connectors. The
above can occur singularly or in combination. Experience to date
indicates that the most common problems are missing load coils,
reversed load coil windings or bridge taps.
(g) Cable insertion loss measurement (carrier frequencies). (1)
When specified by the borrower, carrier frequency insertion loss
measurements shall be made on cable pairs used for T1, T1C, and/or
station carrier systems. Carrier frequency insertion loss shall be made
on a minimum of three pairs. Select at least one pair near the outside
of the core unit layup. If the three measured pairs are within 10% of
the calculated loss in dB corrected for temperature, no further testing
is necessary. If any of the measured pairs of a section are not within
10% of the calculated loss in dB, all pairs in that section used for
carrier transmission shall be measured.
(2) Method of measurement. The step-by-step method of measurement
shall be as shown in Figure 11.
(3) Test equipment. The test equipment is shown in Figure 11 as
follows:
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[GRAPHIC] [TIFF OMITTED] TR02MY97.033
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[[Page 23985]]
(4) Applicable results. (i) The highest frequency to be measured is
determined by the type of carrier system. For T1 type carrier, the
highest frequency is normally 772 kHz. For T1C type carrier, the
highest frequency is normally 1576 kHz. The highest frequency to be
measured for station carrier is 140 kHz.
(ii) The measured insertion loss of the cable shall be within
10% of the calculated loss in dB when the loss is corrected
for temperature.
(iii) The calculated insertion loss is computed as follows:
(A) Multiply the length of each different gauge by the applicable
dB per unit length as shown in Table 7 or 8 as follows:
Table 7.--Cable Attenuation @ 68 deg.F (20 deg.C) Filled Cables--Solid Insulation
----------------------------------------------------------------------------------------------------------------
Frequency (kHz) Attenuation dB/mile (dB/km) Gauge (AWG)
----------------------------------------------------------------------------------------------------------------
19 22 24 26
----------------------------------------------------------------------------------------------------------------
10.......................................... 2.8 (1.7) 4.8 (2.9) 6.4 (3.9) 8.5 (5.3)
20.......................................... 3.2 (2.0) 5.8 (3.6) 8.2 (5.1) 11.2 (6.9)
40.......................................... 3.6 (2.2) 6.5 (4.0) 9.6 (6.0) 13.9 (8.6)
60.......................................... 4.0 (2.5) 6.9 (4.2) 10.3 (6.4) 15.2 (9.4)
80.......................................... 4.5 (2.8) 7.3 (4.5) 10.7 (6.6) 16.0 (9.9)
100......................................... 4.9 (3.0) 7.7 (4.7) 11.1 (6.8) 16.5 (10.2)
112......................................... 5.2 (3.2) 8.0 (4.9) 11.3 (7.0) 16.8 (10.5)
120......................................... 5.4 (3.3) 8.1 (5.0) 11.5 (7.1) 17.0 (10.6)
140......................................... 5.8 (3.6) 8.6 (5.3) 11.9 (7.4) 17.4 (10.8)
160......................................... 6.2 (3.8) 9.0 (5.6) 12.3 (7.6) 17.8 (11.1)
180......................................... 6.6 (4.1) 9.5 (5.9) 12.7 (7.9) 18.2 (11.3)
200......................................... 7.0 (4.3) 10.0 (6.2) 13.2 (8.2) 18.6 (11.5)
300......................................... 8.7 (5.4) 12.2 (7.5) 15.4 (9.6) 20.6 (12.8)
400......................................... 10.0 (6.2) 14.1 (8.8) 17.7 (11.0) 22.9 (14.2)
500......................................... 11.2 (6.9) 15.9 (9.8) 19.8 (12.3) 25.2 (15.6)
600......................................... 12.2 (7.5) 17.5 (10.9) 21.8 (13.6) 27.4 (17.0)
700......................................... 13.2 (8.2) 19.0 (11.8) 23.6 (14.7) 29.6 (18.4)
772......................................... 13.8 (8.5) 19.9 (12.4) 24.8 (15.4) 31.4 (19.5)
800......................................... 14.2 (8.8) 20.1 (12.5) 27.4 (17.1) 31.7 (19.7)
900......................................... 14.8 (9.2) 21.6 (13.4) 29.0 (18.0) 33.8 (21.0)
1000........................................ 15.8 (9.8) 22.7 (14.1) 31.1 (19.3) 35.9 (22.3)
1100........................................ 16.4 (10.2) 23.8 (14.8) 32.7 (20.3) 38.0 (23.6)
1200........................................ 17.4 (10.8) 24.8 (15.4) 34.3 (21.3) 40.0 (24.9)
1300........................................ 17.9 (11.1) 25.9 (16.1) 35.4 (22.0) 41.7 (25.9)
1400........................................ 19.0 (11.8) 26.9 (16.7) 37.0 (23.0) 43.3 (26.9)
1500........................................ 19.5 (12.1) 28.0 (17.4) 38.0 (23.6) 44.3 (27.6)
1576........................................ 20.1 (12.4) 29.0 (18.0) 39.0 (24.3) 44.4 (28.2)
----------------------------------------------------------------------------------------------------------------
Table 8.--Cable Attenuation @ 68 deg.F (20 deg.C) Filled Cables--Expanded Insulation
----------------------------------------------------------------------------------------------------------------
Attenuation dB/mile (dB/km) Gauge (AWG)
Frequency (kHz) -------------------------------------------------------------------
19 22 24 26
----------------------------------------------------------------------------------------------------------------
10.......................................... 3.0 (1.8) 4.9 (3.0) 6.5 (4.0) 8.6 (5.3)
20.......................................... 3.5 (2.1) 6.0 (4.1) 8.5 (5.2) 11.5 (7.1)
40.......................................... 4.0 (2.5) 7.0 (4.3) 10.2 (6.3) 14.4 (8.9)
60.......................................... 4.5 (2.8) 7.5 (4.6) 11.1 (6.8) 16.0 (9.9)
80.......................................... 5.2 (3.3) 7.9 (4.9) 11.3 (6.9) 16.2 (10.1)
100......................................... 5.8 (3.6) 8.4 (5.2) 11.6 (7.2) 16.4 (10.2)
112......................................... 6.0 (3.8) 8.8 (5.4) 11.9 (7.4) 16.6 (10.3)
120......................................... 6.2 (3.9) 9.0 (5.6) 12.1 (7.5) 16.9 (10.5)
140......................................... 6.6 (4.1) 9.5 (5.9) 12.7 (7.9) 17.2 (10.7)
160......................................... 6.9 (4.3) 10.0 (6.2) 13.2 (8.2) 17.4 (10.8)
180......................................... 7.4 (4.6) 10.6 (6.6) 13.7 (8.5) 17.9 (11.1)
200......................................... 7.9 (4.9) 11.1 (6.9) 14.2 (8.8) 18.5 (11.5)
300......................................... 9.5 (5.9) 13.2 (8.2) 16.8 (10.5) 21.6 (13.4)
400......................................... 11.1 (6.9) 15.3 (9.5) 19.5 (12.1) 24.3 (15.1)
500......................................... 12.1 (7.5) 17.9 (11.1) 22.2 (13.8) 27.4 (17.1)
600......................................... 13.7 (8.5) 19.5 (12.1) 24.3 (15.1) 29.6 (18.4)
700......................................... 14.8 (9.2) 21.1 (13.1) 26.4 (16.4) 32.2 (20.0)
772......................................... 15.3 (9.5) 21.6 (13.4) 27.4 (17.1) 33.8 (21.90)
800......................................... 15.8 (9.8) 22.2 (13.8) 28.0 (17.4) 34.4 (21.3)
900......................................... 17.0 (10.5) 23.8 (14.8) 29.6 (18.4) 36.4 (22.6)
1000........................................ 17.4 (10.8) 24.8 (15.4) 31.1 (19.3) 38.5 (23.9)
1100........................................ 17.9 (11.1) 26.4 (16.4) 33.3 (20.7) 40.6 (25.3)
1200........................................ 19.0 (11.8) 27.4 (17.1 34.3 (21.3) 42.2 (26.2)
1300........................................ 19.5 (12.1) 28.5 (17.7) 35.9 (22.3) 43.8 (27.2)
1400........................................ 20.1 (12.5 29.6 (18.4) 37.0 (23.0) 45.9 (28.5)
1500........................................ 20.6 (12.8) 30.6 (19.0) 38.5 (23.9) 47.5 (29.5)
1576........................................ 21.6 (13.4) 31.1 (19.3) 39.1 (24.3) 48.6 (30.2)
----------------------------------------------------------------------------------------------------------------
[[Page 23986]]
(B) Add the individual losses for each gauge to give the total
calculated insertion loss at a temperature of 68 deg.F (20 deg.C);
(C) Correct the total calculated insertion loss at the temperature
of 68 deg.F (20 deg.C) to the measurement temperature by the following
formulae:
At = A68 x [1 + 0.0012 x (t -- 68)] for
English Units
At = A20 x [1 + 0.0022 x (t--20)] for Metric
Units
Where:
At = Insertion loss at the measurement temperature in
dB.
A68 = Insertion loss at a temperature of 68 deg.F in dB.
A20 = Insertion loss at a temperature of 20 deg.C in dB.
t = Measurement temperature in deg.F or ( deg.C); and
(D) Compare the calculated insertion loss at the measurement
temperature to the measured insertion loss to determine compliance with
the requirement specified in paragraph (g)(4)(ii) of this section.
(Note: Attenuation varies directly with temperature. For each
10 deg.F (5.6 deg.C) change in temperature increase or
decrease the attenuation by 1%.)
(iv) If the measured value exceeds the 10% allowable
variation, the cause shall be determined and corrective action shall be
taken to remedy the problem.
(5) Data record. Results of carrier frequency insertion loss
measurements for station, T1, and/or T1C type carrier shall be
recorded. Suggested formats similar to Format III, Outside Plant
Acceptance Tests--T1 or T1C Carrier Pairs, and Format IV, Outside Plant
Acceptance Tests--Station Carrier Pairs, in Sec. 1755.407 or formats
specified in the applicable construction contract may be used.
(6) Probable causes for nonconformance. If the measured loss is
low, the cable records are likely to be in error. If the measured loss
is high, there may be bridge taps, load coils or voice frequency build-
out capacitors connected to the cable pairs or the cable records may be
in error. Figures 12 and 13 are examples that show the effects of
bridge taps and load coils in the carrier path. Figures 12 and 13 are
as follows:
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[[Page 23988]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.035
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[[Page 23989]]
Sec. 1755.404 Fiber optic cable telecommunications plant measurements.
(a) Armor continuity. (1) Tests and measurements shall be made to
ensure that the armor of fiber optic cables is continuous. There are
two areas of concern. The first is armor bonding within a splice and
the second is armor continuity between splices.
(2) Measurement techniques outlined here for verification of armor
continuity are applicable to buried fiber optic cable plant.
Measurements of armor continuity between splices in aerial, armored,
fiber optic cable should be made prior to completion of splicing.
Conclusive results cannot be obtained on aerial plant after all bonds
have been completed to the supporting strand, multigrounded neutral,
etc.
(3) Method of measurement. Armor continuity within splices shall be
measured with a cable shield splice continuity test set. The step-by-
step measurement procedure outlined in the manufacturer's operating
instructions for the specific test equipment being used shall be
followed.
(4) Test equipment. A cable shield splice continuity tester shall
be used to measure armor continuity within splices.
(5) Applicable results. When utilizing shield continuity testers to
measure armor continuity within splices, refer to the manufacturer's
published information covering the specific test equipment to be used
and for anticipated results.
(6) Data record. Measurement data from armor continuity tests shall
be recorded together with anticipated values in an appropriate format
to permit comparison. The recorded data shall include specific
location, cable size, and cable type, if known, etc.
(7) Probable causes for nonconformance. Among probable causes for
nonconformance are broken or damaged armors, bad bonding harnesses,
poorly connected bonding clamps, loose bonding lugs, etc.
(b) Fiber optic splice loss measurement. (1) After placement of all
fiber optic cable plant has been completed and spliced together to form
a continuous optical link between end termination points, splice loss
measurements shall be performed on all field and central office splice
points.
(2) Method of measurement. (i) Field splice loss measurements shall
be made between the end termination points at 1310 and/or 1550
nanometers for single mode fibers and in accordance with Figure 14. Two
splice loss measurements shall be made between the end termination
points. The first measurement shall be from termination point A to
termination point B. The second measurement shall be from termination
point B to termination point A.
(ii) CO splice loss measurements shall be made at 1310 and/or 1550
nanometers for single mode fibers and in accordance with Figure 15. Two
splice loss measurements shall be made between the end termination
points. The first measurement shall be from termination point A to
termination point B. The second measurement shall be from termination
point B to termination point A.
(3) Test equipment. The test equipment is shown in Figures 14 and
15. The optical time domain reflectometer (OTDR) used for the testing
should have dual wave length capability. Figures 14 and 15 are as
follows:
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[[Page 23991]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.037
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[[Page 23992]]
(4) Applicable results. (i) The splice loss for each single mode
field splice shall be the bi-directional average of the two OTDR
readings. To calculate the actual splice loss, substitute the OTDR
readings maintaining the sign of the loss (+) or apparent gain (-) into
the following equation:
[GRAPHIC] [TIFF OMITTED] TR02MY97.021
(ii) When specified in the applicable construction contract, the
splice loss of each field splice at 1310 and/or 1550 nanometers shall
not exceed the limit specified in the contract.
(iii) When no limit is specified in the applicable construction
contract, the splice loss of each field splice shall not exceed 0.2 dB
at 1310 and/or 1550 nanometers.
(iv) The splice loss for each single mode CO splice shall be the
bi-directional average of the two OTDR reading. To calculate actual
splice loss, substitute the OTDR reading, maintaining the sign of the
loss (+) or apparent gain (-), into the equation specified in paragraph
(b)(4)(i) of this section.
(v) When specified in the applicable construction contract, the
splice loss of each central office splice at 1310 and/or 1550
nanometers shall not exceed the limit specified in the contract.
(vi) When no limit is specified in the applicable construction
contract, the splice loss of each central office splice shall not
exceed 1.2 dB at 1310 and/or 1550 nanometers.
(5) Data record. The measurement data shall be recorded. A
suggested format similar to Format V, Outside Plant Acceptance Test--
Fiber Optic Telecommunications Plant, in Sec. 1755.407 or a format
specified in the applicable construction contract may be used.
(6) Probable causes for nonconformance. When the results of the
splice loss measurements exceed the specified limits the following
factors should be checked:
(i) Proper end preparation of the fibers;
(ii) End separation between the fiber ends;
(iii) Lateral misalignment of fiber cores;
(iv) Angular misalignment of fiber cores;
(v) Fresnel reflection;
(vi) Contamination between fiber ends;
(vii) Core deformation; or
(viii) Mode-field diameter mismatch.
(c) End-to-end attenuation measurement. (1) After placement of all
fiber optic cable plant has been completed and spliced together to form
a continuous optical link between end termination points, end-to-end
attenuation measurements shall be performed on each optical fiber
within the cable.
(2) Method of measurement. For single mode fibers, the end-to-end
attenuation measurements of each optical fiber at 1310 and/or 1550
nanometers in each direction between end termination points shall be
performed in accordance with Figure 16.
(3) Test equipment. The test equipment is shown in Figure 16 as
follows:
BILLING CODE 3410-15-P
[[Page 23993]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.038
BILLING CODE 3410-15-C
[[Page 23994]]
(4) Applicable results. The end-to-end attenuation of each single
mode optical fiber at 1310 and/or 1550 nanometers shall not exceed the
limits specified in the applicable construction contract.
(5) Data record. The measurement data shall be recorded. A
suggested format similar to Format V for fiber optic telecommunications
plant in Sec. 1755.407 or on a format specified in the applicable
construction contract may be used.
(6) Probable causes for nonconformance. Failure of each optical
fiber to meet the end-to-end attenuation limit could be attributed to
the following:
(i) Excessive field or central office splice loss;
(ii) Excessive cable attenuation; or
(iii) Damage to the fiber optic cable during installation.
(d) End-to-end fiber signature measurement. (1) After placement of
all fiber optic cable plant has been completed and spliced together to
form a continuous optical link between end termination points, end-to-
end fiber signature testing shall be performed on each optical fiber
within the cable.
(2) Method of measurement. For single mode fibers, the end-to-end
fiber signature measurement of each optical fiber in each direction
shall be performed between end termination points at 1310 and/or 1550
nanometers in accordance with Figure 17.
(3) Test equipment. The test equipment is shown in Figure 17 as
follows:
BILLING CODE 3410-15-P
[[Page 23995]]
[GRAPHIC] [TIFF OMITTED] TR02MY97.039
BILLING CODE 3410-15-C
[[Page 23996]]
(4) Applicable results. The appearance of each optical fiber
between end termination points.
(5) Data record. Plot the trace of each optical fiber and retain as
a permanent record for future comparison if needed.
(6) Probable causes for nonconformance. None.
Sec. 1755.405 Voiceband data transmission measurements.
(a) The data transmission measurements listed in this section shall
be used to determine the acceptability of trunk and nonloaded
subscriber loop circuits for data modem transmission.
(b) Signal-to-C notched noise (S/CNN) measurement. (1) When
specified by the borrower, S/CNN measurements shall be made on trunk
circuits and nonloaded subscriber loops. For trunk circuits, the
measurement shall be made between CO locations. For nonloaded
subscriber loops, the measurement shall be made from the CO to the
station protector of the NID at the customer's access location.
(2) S/CNN is the logarithmic ratio expressed in dB of a 1,004 Hz
holding tone signal compared to the C-message weighted noise level. S/
CNN is one of the most important transmission parameters affecting the
performance of data transmission because proper modem operation
requires low noise relative to received power level. Since modulated
carriers are used in data communication systems, noise measurements
need to be performed with power on the connection to activate equipment
having signal-level-dependent noise sources. For 4 kHz channels, a
1,004 Hz holding tone is used to activate the signal-dependent
equipment on the channel or connection.
(3) Method of measurement. The S/CNN measurement shall be made
using a 1,004 Hz holding tone at -13 dBm0 (decibels relative to one
milliwatt, referred to a zero transmission level point) and performed
in accordance with American National Standards Institute (ANSI) T1.506-
1990, American National Standard for Telecommunications--Network
Performance--Transmission Specifications for Switched Exchange Access
Network including supplement ANSI T1.506a-1992, and American National
Standards Institute/Institute of Electrical and Electronics Engineers
(ANSI/IEEE) 743-1984, IEEE Standard Methods and Equipment for Measuring
the Transmission Characteristics of Analog Voice Frequency Circuits.
The ANSI T1.506-1990, American National Standard for
Telecommunications--Network Performance--Transmission Specifications
for Switched Exchange Access Network is incorporated by reference in
accordance with 5 U.S.C. 522(a) and 1 CFR part 51. Copies of ANSI
T1.506-1990 are available for inspection during normal business hours
at RUS, room 2845, U.S. Department of Agriculture, STOP 1598,
Washington, DC 20250-1598 or at the Office of the Federal Register, 800
North Capitol Street, NW., suite 700, Washington, DC. Copies are
available from ANSI, Customer Service, 11 West 42nd Street, New York,
New York 10036, telephone number (212) 642-4900. The ANSI/IEEE 743-
1984, IEEE Standard Methods and Equipment for Measuring the
Transmission Characteristics of Analog Voice Frequency Circuits is
incorporated by reference in accordance with 5 U.S.C. 522(a) and 1 CFR
part 51. Copies of ANSI/IEEE 743-1984 are available for inspection
during normal business hours at RUS, room 2845, U.S. Department of
Agriculture, STOP 1598, Washington, DC 20250-1598 or at the Office of
the Federal Register, 800 North Capitol Street, NW., suite 700,
Washington, DC. Copies are available from ANSI, Customer Service, 11
West 42nd Street, New York, New York 10036, telephone number (212) 642-
4900.
(4) Test equipment. The equipment for performing the measurement
shall be in accordance with ANSI/IEEE 743-1984.
(5) Applicable results. The S/CNN for both trunk and nonloaded
subscriber loop circuits shall not be less than 31 dB.
(6) Data record. The measurement data shall be recorded. Suggested
formats similar to Format VI, Voiceband Data Transmission Tests--
Nonloaded Subscriber Loops, and Format VII, Voiceband Data Transmission
Tests--Trunk Circuits, in Sec. 1755.407 or formats specified in the
applicable construction contract may be used.
(7) Probable causes for nonconformance. Some of the causes for
failing to obtain the desired results may be due to excessive harmonic
distortion, quantizing noise, phase and amplitude jitter, and loss in
digital pads used for level settings.
(c) Signal-to-intermodulation distortion (S/IMD) measurement. (1)
When specified by the borrower, S/IMD measurements shall be made on
trunk circuits and nonloaded subscriber loops. For trunk circuits, the
measurement shall be made between CO locations. For nonloaded
subscriber loops, the measurement shall be made from the CO to the
station protector of the NID at the customer's access location.
(2) S/IMD is a measure of the distortion produced by extraneous
frequency cross products, known as intermodulation products, when a
multi-tone tone signal is applied to a system.
(3) Intermodulation distortion (IMD) is caused by system
nonlinearities acting upon the harmonic frequencies produced from an
input of multiple tones. The products resulting from IMD can be more
damaging than noise in terms of producing data transmission errors.
(4) IMD is measured as a signal to distortion ratio and is
expressed as the logarithmic ratio in dB of the composite power of four
resulting test frequencies to the total power of specific higher order
distortion products that are produced. The higher order products are
measured at both the 2nd order and 3rd order and are designated R2 and
R3, respectively. The four frequency testing for IMD is produced with
four tones of 857, 863, 1,372, and 1,388 Hz input at a composite power
level of -13 dBm0.
(5) Method of measurement. The S/IMD measurement shall be performed
in accordance with ANSI T1.506-1990 and ANSI/IEEE 743-1984.
(6) Test equipment. The equipment for performing the measurement
shall be in accordance with ANSI/IEEE 743-1984.
(7) Applicable results. The 2nd order (R2) S/IMD for both trunk and
nonloaded subscriber loop circuits shall not be less than 40 dB. The
3rd order (R3) S/IMD for both trunk and nonloaded subscriber loop
circuits shall not be less than 40 dB.
(8) Data record. The measurement data shall be recorded. Suggested
formats similar to Format VI for nonloaded subscriber loops and Format
VII for trunk circuits in Sec. 1755.407 or formats specified in the
applicable construction contract may be used.
(9) Probable causes for nonconformance. Some of the causes for
failing to obtain the desired results may be due to channel
nonlinearities, such as compression and clipping, which cause harmonic
and intermodulation distortion in a voiceband signal.
(d) Envelope delay distortion (EDD) measurement. (1) When specified
by the borrower, EDD measurements shall be made on trunk circuits and
nonloaded subscriber loops. For trunk circuits, the measurement shall
be made between CO locations. For nonloaded subscriber loops, the
measurement shall be made from the CO to the station protector of the
NID at the customer's access location.
[[Page 23997]]
(2) EDD is a measure of the linearity or uniformity of the phase
versus frequency characteristics of a transmission facility. EDD is
also known as relative envelope delay (RED).
(3) EDD is specifically defined as the delay relative to the
envelope delay at the reference frequency of 1,704 Hz. EDD is typically
measured at two frequencies, one low and one high in the voiceband. The
low frequency measurement is made at 604 Hz. The high frequency
measurement is made at 2,804 Hz.
(4) Method of measurement. The EDD measurement shall be performed
in accordance with ANSI T1.506-1990 and ANSI/IEEE 743-1984.
(5) Test equipment. The equipment for performing the measurement
shall be in accordance with ANSI/IEEE 743-1984.
(6) Applicable results. The EDD for both trunk and nonloaded
subscriber loop circuits at the low frequency of 604 Hz shall not
exceed 1,500 microseconds. The EDD for both trunk and nonloaded
subscriber loop circuits at the high frequency of 2,804 Hz shall not
exceed 1,000 microseconds.
(7) Data record. The measurement data shall be recorded. Suggested
formats similar to Format VI for nonloaded subscriber loops and Format
VII for trunk circuits in Sec. 1755.407 or formats specified in the
applicable construction contract may be used.
(8) Probable causes for nonconformance. Some of the causes for
failing to obtain the desired results may be due to nonlinearity of the
phase versus frequency characteristic of the transmission facility.
This nonlinear phase versus frequency characteristic of the
transmission facility causes the various frequency components to travel
at different transit times which results in successively transmitted
data pulses to overlap at the receive end. The overlapping of the
pulses at the receive end results in distortion of the received signal.
Excessive EDD on the transmission facility may be reduced using data
modems with equalization or by conditioning the transmission line.
(e) Amplitude jitter (AJ) measurement. (1) When specified by the
borrower, AJ measurements shall be made on trunk circuits and nonloaded
subscriber loops. For trunk circuits, the measurement shall be made
between CO locations. For nonloaded subscriber loops, the measurement
shall be made from the CO to the station protector of the NID at the
customer's access location.
(2) AJ is any fluctuation in the peak amplitude value of a fixed
tone signal at 1,004 Hz from its nominal value. AJ is expressed in peak
percent amplitude modulation.
(3) AJ is measured in two separate frequency bands, 4-300 Hz and
20--300 Hz. The 4--300 Hz band is important for modems employing echo
canceling capabilities. The 20-300 Hz band is used for modems that do
not employ echo cancelers.
(4) Amplitude modulation can affect the error performance of
voiceband data modems. The measurement of amplitude jitter indicates
the total effect on the amplitude of the holding tone of incidental
amplitude modulation and other sources including quantizing and message
noise, impulse noise, gain hits, phase jitter, and additive tones such
as single-frequency interference.
(5) Method of measurement. The AJ measurement shall be performed in
accordance with ANSI T1.506-1990 and ANSI/IEEE 743-1984.
(6) Test equipment. The equipment for performing the measurement
shall be in accordance with ANSI/IEEE 743-1984.
(7) Applicable results. The AJ for both trunk and nonloaded
subscriber loop circuits in the 4--300 Hz frequency band shall not
exceed 6%. The AJ for both trunk and nonloaded subscriber loop circuits
in the 20--300 Hz frequency band shall not exceed 5%.
(8) Data record. The measurement data shall be recorded. Suggested
formats similar to Format VI for nonloaded subscriber loops and Format
VII for trunk circuits in Sec. 1755.407 or formats specified in the
applicable construction contract may be used.
(9) Probable causes for nonconformance. Some of the causes for
failing to obtain the desired results may be due to excessive S/CNN,
impulse noise, and phase jitter.
(f) Phase jitter (PJ) measurement. (1) When specified by the
borrower, PJ measurements shall be made on trunk circuits and nonloaded
subscriber loops. For trunk circuits, the measurement shall be made
between CO locations. For nonloaded subscriber loops, the measurement
shall be made from the CO to the station protector of the NID at the
customer's access location.
(2) PJ is any fluctuation in the zero crossings of a fixed tone
signal (usually 1,004 Hz) from their nominal position in time within
the voiceband. PJ is expressed in terms of either degrees peak-to-peak
( deg.p-p) or in terms of a Unit Interval (UI). One UI is equal to
360 deg. p-p.
(3) PJ measurements are typically performed in two nominal
frequency bands. The frequency bands are 20-300 Hz band and either the
2-300 Hz band or the 4-300 Hz band. The 20-300 Hz band is important to
all phase-detecting modems. The 4-300 Hz band or the 2-300 Hz band is
important for modems employing echo canceling capabilities.
(4) Phase jitter can affect the error performance of voiceband data
modems that use phase detection techniques. The measurement of phase
jitter indicates the total effect on the holding tone of incidental
phase modulation and other sources including quantizing and message
noise, impulse noise, phase hits, additive tones such as single-
frequency interference, and digital timing jitter.
(5) Method of measurement. The PJ measurement shall be performed in
accordance with ANSI T1.506-1990 and ANSI/IEEE 743-1984.
(6) Test equipment. The equipment for performing the measurement
shall be in accordance with ANSI/IEEE 743-1984.
(7) Applicable results. The PJ for both trunk and nonloaded
subscriber loop circuits in the 4-300 Hz frequency band shall not
exceed 6.5 deg. p-p. The PJ for both trunk and nonloaded subscriber
loop circuits in the 20-300 Hz frequency band shall not exceed
10.0 deg. p-p.
(8) Data record. The measurement data shall be recorded. Suggested
formats similar to Format VI for nonloaded subscriber loops and Format
VII for trunk circuits in Sec. 1755.407 or formats specified in the
applicable construction contract may be used.
(9) Probable causes for nonconformance. Some of the causes for
failing to obtain the desired results may be due to excessive S/CNN,
impulse noise, and amplitude jitter.
(g) Impulse noise measurement. (1) When specified by the borrower,
impulse noise measurements shall be made on trunk circuits and
nonloaded subscriber loops. For trunk circuits, the measurement shall
be made between CO locations. For nonloaded subscriber loops, the
measurement shall be made from the CO to the station protector of the
NID at the customer's access location.
(2) Impulse noise is a measure of the presence of unusually large
noise excursions of short duration that are beyond the normal
background noise levels on a facility. Impulse noise is typically
measured by counting the number of occurrences beyond a particular
noise reference threshold in a given time interval. The noise reference
level is C-message weighted.
(3) Method of measurement. The impulse noise measurement shall be
performed using a 1,004 Hz tone at -13 dBm0 and in accordance with ANSI
T1.506-1990 and ANSI/IEEE 743-1984.
[[Page 23998]]
(4) Test equipment. The equipment for performing the measurement
shall be in accordance with ANSI/IEEE 743-1984.
(5) Applicable results. The impulse noise for both trunk and
nonloaded subscriber loop circuits shall not exceed 65 dBrnC0 (decibels
relative to one picowatt reference noise level, measured with C-message
frequency weighting, referred to a zero transmission level point). The
impulse noise requirement shall be based upon a maximum of 5 counts in
a 5 minute period at equal to or greater than the indicated noise
thresholds.
(6) Data record. The measurement data shall be recorded. Suggested
formats similar to Format VI for nonloaded subscriber loops and Format
VII for trunk circuits in Sec. 1755.407 or formats specified in the
applicable construction contract may be used.
(7) Probable causes for nonconformance. Some of the causes for
failing to obtain the desired results may be due to excessive transient
signals originating from the various switching operations.
Sec. 1755.406 Shield or armor ground resistance measurements.
(a) Shield or armor ground resistance measurements shall be made on
completed lengths of copper cable and wire plant and fiber optic cable
plant.
(b) Method of measurement. (1) The shield or armor ground
resistance measurement shall be made between the copper cable and wire
shield and ground and between the fiber optic cable armor and ground,
respectively. The measurement shall be made either on cable and wire
lengths before splicing and before any ground connections are made to
the cable or wire shields or armors. Optionally, the measurement may be
made on cable and wire lengths after splicing, but all ground
connections must be removed from the section under test.
(2) The method of measurement using either an insulation resistance
test set or a dc bridge type megohmmeter shall be as shown in Figure 18
as follows:
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(c) Test equipment. (1) The shield or armor ground resistance
measurements may be made using an insulation resistance test set, a dc
bridge type megohmmeter, or a commercially available fault locator.
(2) The insulation resistance test set should have an output
voltage not to exceed 500 volts dc and may be hand cranked or battery
operated.
(3) The dc bridge type megohmmeter, which may be ac powered, should
have scales and multipliers which make it possible to accurately read
resistance values of 50,000 ohms to 10 megohms. The voltage that is
applied to the shield or armor during the test should not be less than
``250 volts dc'' nor greater than ``1,000 volts dc'' when using an
instrument having adjustable test voltage levels.
(4) Commercially available fault locators may be used in lieu of
the above equipment, if the devices are capable of detecting faults
having resistance values of 50,000 ohms to 10 megohms. Operation of the
devices and method of locating the faults should be in accordance with
manufacturer's instructions.
(d) Applicable results. (1) For all new copper cable and wire
facilities and all new fiber optic cable facilities, the shield or
armor ground resistance levels normally exceed 1 megohm-mile (1.6
megohm-km) at 68 deg.F (20 deg.C). A value of 100,000 ohm-mile (161,000
ohm-km) at 68 deg.F (20 deg.C) shall be the minimum acceptable value of
the shield or armor ground resistance.
(2) Shield or armor ground resistance varies inversely with length
and temperature. In addition other factors which may affect readings
could be soil conditions, faulty test equipment and incorrect test
procedures.
(3) For the resistance test method and dc bridge type megohmmeter,
the ohm-mile (ohm-km) value for the shield or armor ground resistance
shall be computed by multiplying the actual scale reading in ohms on
the test set by the length in miles (km) of the cable or wire under
test.
(4)(i) The objective shield or armor ground resistance may be
determined by dividing 100,000 by the length in miles (161,000 by the
length in km) of the cable or wire under test. The resulting value is
the minimum acceptable meter scale reading in ohms. Examples for
paragraphs (d)(3) and (d)(4) of this section are as follows:
Equation 1. Test Set: Scale Reading * Length = Resistance-Length
75,000 ohms * 3 miles = 225,000 ohm-mile
(75,000 ohms * 4.9 km = 367,000 ohm-km)
Equation 2. 100,000 ohm-mile ' Length = Minimum Acceptable
Meter Scale Reading
100,000 ohm-mile ' 3 miles = 33,333 ohms
(161,000 ohm-km ' 4.9 km = 32,857 ohms)
(ii) Since the 33,333 ohms (32,857 ohms) is the minimum acceptable
meter scale reading and the meter scale reading was 75,000 ohms, the
cable is considered to have met the 100,000 ohm-mile (161,000 ohm-km)
requirement.
(5) Due to the differences between various jacketing materials used
in manufacturing cable or wire and to varying soil conditions, it is
impractical to provide simple factors to predict the magnitude of
variation in shield or armor to ground resistance due to temperature.
The variations can, however, be substantial for wide excursions in
temperature from the ambient temperature of 68 deg.F (20 deg.C).
(e) Data record. The data shall be corrected to the length
requirement of ohm-mile (ohm-km) and a temperature of 68 deg.F
(20 deg.C) and shall be recorded on a form specified in the applicable
construction contract.
(f) Probable causes for nonconformance. (1) When results of
resistance measurements are below the 100,000 ohm-mile (161,000 ohm-km)
requirement at 68 deg.F (20 deg.C), the jacket temperature, soil
conditions, test equipment and method shall be reviewed before the
cable or wire is considered a failure. If the temperature is
approximately 68 deg.F (20 deg.C) and soil conditions are acceptable,
and a reading of less than 100,000 ohm-mile (161,000 ohm-km) is
indicated, check the calibration of the equipment; as well as, the test
method. If the equipment was found to be out of calibration,
recalibrate the equipment and remeasure the cable or wire. If the
temperature was 86 deg.F (30 deg.C) or higher, the cable or wire shall
be remeasured at a time when the temperature is approximately 68 deg.F
(20 deg.C). If the test was performed in unusually wet soil, the cable
or wire shall be retested after the soil has reached normal conditions.
If after completion of the above steps, the resistance value of 100,000
ohm-mile (161,000 ohm-km) or greater is obtained, the cable or wire
shall be considered acceptable.
(2) When the resistance value of the cable or wire is still found
to be below 100,000 ohm-mile (161,000 ohm-km) requirement after
completion of the steps listed in paragraph (f)(1) of this section, the
fault shall be isolated by performing shield or armor ground resistance
measurements on individual cable or wire sections.
(3) Once the fault or faults have been isolated, the cable or wire
jacket shall be repaired in accordance with Sec. 1755.200, RUS Standard
for Splicing Copper and Fiber Optic Cables or the entire cable or wire
section may be replaced at the request of the borrower.
Sec. 1755.407 Data formats.
The following suggested formats listed in this section may be used
for recording the test data:
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Dated: April 24, 1997.
Jill Long Thompson,
Under Secretary, Rural Development.
[FR Doc. 97-11316 Filed 5-1-97; 8:45 am]
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