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S/N: 19970007 c 1997 3M Ver 1.01 USA

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DynatelTM Systems

Prepared By: Roger C. Valencia US and International Technical Service Engineer 3M Test & Measurement Systems 3M Austin Center Austin, TX, USA - January 1999

Outside Plant Telephone Cable Testing & Fault Locating 1

The Telephone Outside Plant [OSP]

Aer

480

ial

Cab

le

Sys

tem

TURBO

ice l Off a r t Cen

lcoM e T D XYZ

m yste ble S a C ied Bur t c e r Di

X-Connect Boxes

F Manholes

lt Vau e l b Ca

Und

erg

rou

nd

Cab

VO

YK 749

M a n h o l e s

le

Sys

tem

2

Vertical Frame

The Telephone Outside Plant [ OSP ]

CO MDF

Horizontal Frame

TSPS *

Switch Jumper Wires CAMA **

Protectors

Underground Plant

Manhole

Tip Cables Feeder Cable

* T raffic S ervice P osition S ystem

Operator-assisted long distance calls

** C entralized A utomatic M essage A ccounting

Computerized billing equipment for long distance calls

Manhole Cable Vault Distribution Cable

Aerial Plant

Distribution Cables

Subscriber X-Connect Boxes

Protector Box

Subscriber Direct-Buried Plant

Direct-Buried Drop Wire

3

The

Telephone Cable [Definition] It is one of several other types of communication facilities or media which is generally made up of paired, insulated copper conductors called TIP [A] and RING [B]. A cable can consist a few pairs, hundreds of pairs or thousands of pairs and the conductors can be of different sizes or gauges depending upon system requirements.

Other types of Communication Facilities

OPEN WIRE SYSTEMS [ Telegraph ] COAXIAL SYSTEMS [ CATV ] RADIO SYSTEMS [ Microwave, Cellular ] COMMUNICATION SATELLITES [ Disk ] FIBER OPTIC SYSTEMS 4

The Telephone Cable [Basic Construction]

Cable Shield [Corrugated Aluminum ]

Air or Jelly-filled RING [ B ]

Copper Conductors TIP [ A ] Conductor Insulation [ Plastic, Pulp or Paper ]

Outer Cable Jacket [ Plastic ]

5

The origin of the name Tip [A] and Ring [B]

Insulators

Shell

Tip [A]

Sleeve

Tip [A]

Ring [B] Ring [B]

Insulator

Sleeve

6

The

Telephone Cable [ Electrical Representation ]

Cable Shield / Gnd

Tip [A]

Ring [B]

T [A] - Gnd Capacitance

T [A] - Gnd Capacitance

T [A] - Gnd Capacitance

T [A] - Gnd Capacitance

T [A] - Gnd Capacitance

T [A] - R [B] Mutual Capacitance

T [A] - R [B] Mutual Capacitance

T [A] - R [B] Mutual Capacitance

T [A] - R [B] Mutual Capacitance

T [A] - R [B] Mutual Capacitance

R [B] - Gnd Capacitance

R [B] - Gnd Capacitance

R [B] - Gnd Capacitance

R [B] - Gnd Capacitance

R [B] - Gnd Capacitance

Cable Shield / Gnd

7

Effect of Cable Resistance to Signal Transmission Note: In a pure resistive circuit, the transmitted signal will be attenuated but its original shape is maintained. There will 0 dBm [ 1 mw ]

be no distortion of the signal.

- 8.5 dBm

Cable Shield Tip [A]

Transmit Side

Receive Side

Ring [B] Cable Shield

8

Effect of Cable Resistance and Capacitance to Signal Transmission 0 dBm [ 1 mw ]

Note: In a circuit where both resistance and capacitance exist, the transmitted tones were attenuated and their original shapes were also altered or changed. In other words, the signal became distorted.

- 16.5 dBm

High frequencies normally suffers most because of the combined filter effect of cable resistance and capacitance. In the illustration, the high frequency tone was almost totally absorbed by the added capacitance of the cable.

Tip [A]

Transmit

Receive

Ring [B]

Cable Shield

9

RESISTANCE [Definition] It is a natural characteristic of any conductor (i.e. Copper, Aluminum, Nickel, Silver, Gold, etc.) which opposes the flow of electrical current through it. Electric current

IN

OUT Conductor

Conductor Resistance

Available electric current from the battery Conductor Resistance

Battery

Actual current flowing through the circuit due to the conductor resistance. 10

OHM

Unit of measure for Resistance Commonly used units: Ohm

=

0 to 1

Ohms

=

2 to 999

Kilo-Ohms ( K )

=

1000 to 999,999

Mega-Ohms ( M )

=

1,000,000 to 999,999,999

Giga-Ohms

=

1,000,000,000 11

Electrical Length of a Conductor It is the resistance of a conductor in OHMS measured at a certain temperature in oFarenheit or oCentigrade and then converted into DISTANCE (length). Copper W I R E

Plastic Insulation

Conductor Resistance

Ohmmeter

12

Physical Length of a Conductor

It is the length measured with the use of a measuring device like a WHEEL or a RULER Tape.

Conductor

Insulation

0

1

2

3

4

5

6

7

8

9

Measuring Device

13

Conductor Resistance To Distance Conversion Table

Gauge [Size]

Conductor Length

AWG ( mm )

per Ohm

19 AWG ( 0.91 mm )

124.24 ft. ( 37.87 m )

22 AWG ( 0.64 mm )

61.75 ft. (18.82 m)

24 AWG ( 0.51 mm )

38.54 ft. ( 11.75 m )

26 AWG ( 0.41 mm )

24.00 ft. ( 7.32 m )

28 AWG ( 0.32 mm )

15.08 ft ( 4.60 m )

Formulas: 1. For cable temperatures ABOVE 68 oF [ 20oC ] :

Ft = Fa [ 1 - 0.00218 ( t - 68 ) ]

2. For cable temperature BELOW 68 oF [ 20oC ] :

Ft = Fa [ 1 + 0.00218 ( t + 68 ) ] Where: Ft = Feet / Meters per Ohm @ temperature t ( oF / oC ) Fa = Feet / Meters per Ohm @ temperature 68 oF / 20 oC (see table above). 14

The “ TWIST ” Factor Outer Plastic Sheath

Spiral twisting of conductors

The “ Twist ” Factor Cable Shield

Cable Length

3%

Pair Length

Note: The twisting of the conductors inside the cable makes the physical and electrical length of the pair about 3% longer than cable. Ex.: If the electrical length of a pair is 103 feet or meters, this can be translated to 100 feet or meters of cable length.

15

Factors That Affect Resistance 1. Length: The shorter the conductor, the lower its resistance. The longer the conductor, the higher its resistance.

2. Gauge (Size): The bigger the conductor, the lower its resistance. The smaller the conductor, the higher its resistance.

3. Temperature: The lower the conductor’s temperature, the lower its resistance. The higher the conductor’s temperature, the higher its resistance. Therefore: The Length of a conductor is a factor of Gauge (Size) and Temperature.

16

Loop Resistance Tip [A] - R1 Strap Ring [B] - R2

Loop Resistance

= R1 + R2

Resistance to strap

= R1 + R2 2

Ohmmeter

17

Resistive Balance Test Measurement #1

Tip [A] Strap Ring [B] Shield

Measurement #2

Tip [A] Strap Ring [B] Shield

Measurement #3

Tip [A] Strap Ring [B] Shield

Note: For a normal cable --a) Measurement #1 should be equal to Measurement #2 (If they differ by 10% or more, a “partial open” exist in either Tip [A] or Ring [B] or both). b) Measurement #3 = Measurement #1 + Measurement #2 18

More About Resistors

R1 (10)

Rt = R1 + R2 = 10 + 10 = 20 Ohms

R2 (10)

1 R1

R2

(10)

(10)

=

Rt Rt 1

R1 + R2 R1 x

=

100

R2

=

=

10 + 10 10 x 10

=

20

or

100

5 Ohms

20 19

Wheatstone (Resistance) Bridge [ Basic Concept]

A

Conditions for NULL R1

R3

6VDC

6VDC

= R2

R4

R1=120

R3=120

NULL

12VDC

12VDC

Battery

Battery

Galvanometer R2=120

R4=120

6VDC

6VDC

B 20

Wheatstone Bridge [ Precision Ohmmeter ] A RL1

Tip [A]

R1

Strap

R3 NULL Meter

Battery

Battery

Ring [B]

RL2

G Note: R2

R4 (Variable )

R1 & R2 are fixed and ratio is known RL1 + RL2 = Loop resistance [ Tip (A) & Ring (B) ]

B

R4 = Variable Resistor G = Galvanometer [ NULL Meter ] A R1

R3

Conditions for NULL R1

R3 =

R2

R4

R2

R4

B

Basic Wheatstone Bridge 21

Resistance Fault Locate using a Wheatstone Bridge

[ Basic Concept ]

T1 R1

Faulted Conductor

T2

A R3 Fault

DTF (Distance-To-Fault)

DTS (Distance-To-Strap) = 1000 meters

A R1

STF (Strap-To-Fault)

T1

Note: If the bridge nulls at 75 % of DTS (1000 meters) then DTF = 75% of 1000 m = 750 m STF = 25% of 1000 m = 250 m

A

R3 T2

Fault

G R2

R4

R1

R3 G

B Conditions for NULL R1 R3 = R2 R4

B

T1 0%

T2

Slider Arm

R2

R4

100 %

75 % 1000 meters

Dynatel 965 Subscriber Loop Analyzer 22

CAPACITANCE It is the electrical property of a device called “Capacitor” which is created when two or more metallic plates or conductors are placed close to but electrically insulated from each other. Capacitance permits the storage of electrical energy which means that the capacitor can be charged or discharged similar to a rechargeable battery.

Connecting Lead Plate #1

Commonly used dielectric materiasls 1. Paper 2. Ceramic 3. Mylar 4. Polyester 5. Mica 6. Electrolyte

Plate #2 Dielectric [ Insulator ]

Connecting Lead

Basic Construction of a Capacitor

23

Common types of Capacitors 1. Mica 2. Paper 3. Polyester 4. Ceramic

0.0022 0.022/250 5%

Mica Trimmer capacitor

Tubular Paper capacitor

WIMA MKC4

0.1 ufd . 3 50 VD C

Polyester capacitor

50V

Ceramic capacitor

1000 uf 16v 1000

5. Electrolytic

Electrolytic capacitor

24

Factors Affecting Capacitance

Closer Gap Solid Dielectric

Larger Plates

Wider Gap Air Dielectric Smaller Plates

1. The Larger the plates, the higher the capacitance. 2. The closer the plates, the higher the capacitance. 3. Solid dielectric (insulation) materials increases capacitance compared to air. 25

How a Capacitor Works 12 V Charging the capacitor

12 V Charger disconnected

12 V Charge retained

12 V lamp

Lamp lights up until capacitor is fully discharged.

26

More about Capacitors

C1 = 1uF

1

=

Ct 1

C1 = 1uF

=

1 + 1

C1 x C2 =

Ct C2 = 1uF

C1 + C2

2

1

or

1 1

Ct

=

2

= 0.5 uF

C2 = 1uF

Ct = C1 + C2 = 2uF

27

Capacitances on a telephone pair

Tip [A] Ring [B]

Shield

Mutual Capacitance

Ring [B]

Ring [B] to Ground Capacitance

C1

C2

Tip [A]

C3

Tip [A] to Ground Capacitance

Shield

28

Capacitances in a telephone cable

Shield

Ring [B]

Ring [B]

Tip [A]

Tip [A]

29

FARAD Unit of measure for capacitance Commonly-used capacitance units:

Microfarad (uF) = 1 millionth of a FARAD

Nanofarad (nF) = 1 thousanths of a Microfarad

Picofarad (pF) = 1 millionth of a Microfarad

30

Standard Capacitances Of Telephone Cables

Type

Mutual

Tip[A] / Ring[B] To Ground

Aircore

0.083 uF/Mile [ 0.052 uF/Km ]

0.125 uF/Mile [ 0.078 uF/Km ]

Jelly-Filled

0.083 uF/Mile [ 0.052 uF/Km ]

0.140 uF/Mile [ 0.087 uF/Km ]

2-Pair Drop

0.083 uF/Mile [ 0.052 uF/Km ]

0.155 uF/Mile [ 0.096 uF/Km ]

5-Pair Drop

0.083 uF/Mile [ 0.052 uF/Km ]

0.150 uF/Mile [ 0.093 uF/Km ] 31

How A Uniform Mutual Capacitance Of A Telephone Cable Pair Is Achieved Irrespective Of The Different Conductor Sizes (Gauges)

D D

D

Ring[B]

Tip[A]

Tip[A]

Ring[B]

Tip[A]

Ring[B]

Tip[A]

D

Tip[A]

Ring[B]

Ring[B]

Tip[A]

Ring[B]

D D

‘D’istance

=

the same

‘D’istance

=

not the same

‘D’istance

=

not the same

Insulation Thickness

=

the same

Insulation Thickness

=

the same

Insulation Thickness

=

not the same

Size/Gauge

=

not the same

Size/Gauge

=

not the same

Size/Gauge

=

not the same

Mutual Capacitance

=

not the same

Mutual Capacitance

=

not the same

Mutual Capacitance

=

the same

32

How the 965DSP measures capacitance AC current

R = resistance of the conductors to AC R=?

current in ohms.

XL = 0

XL = Inductive reactance - opposition of a

XC = ?

Voltage Lo-Hi Frequency Sweep R=?

coil to AC current in ohms. XC = Capacitive reactance - opposition of a capacitor to AC current in ohms. R + XL + XC = Impedance in ohms.

XL = 0

1. The 965DSP transmits a Lo-Hi frequency sweep at a specified voltage across the circuit where the amount of current flow is determined. Once the amount of circuit current is known, circuit impedance is then calculated. 2. Once the circuit impedance is known, the value of the two unknown factors R = ? Ohms and XC = ? Ohms are calculated with the use of sophisticated mathematical process. 3. When the value of XC is found, it is translated into capacitance and then into distance based on pre-programmed Capacitance-To-Distance table in the software. Example: Impedance

=

600 ohms

R

=

40 ohms

XC

=

560 ohms = 0.083uF = 1 mile (length of cable)

XL

=

0 ohms (insignificant in this example)

33

How length of Tip[A] is measured with the 965DSP “OPEN” Meter Lo-Hi Frequency Sweep

Ring[B]

C1a

C1b

C1c

C2a

C2b

C2c

C3a

C3b

C3c

Red

Blk

Tip[A]

Grn B l k

G r n

Shield

R e d

Note: When the length of Tip[A] is being measured, the Red test lead is shorted to Green (Shield/Ground) through an internal switch thus grounding the Ring[B] conductor. The total capacitive reactance of C3 and C2 (in ohms) translated into distance (in feet or meters) represents the length of Tip[A]. Tip[A]

Ring[B]

Tip[A]

C2

C3

C3

C2

34

How length of Ring[B] is measured with the 965DSP “OPEN” Meter Lo-Hi Frequency Sweep

Ring[B]

C1a

C1b

C1c

C2a

C2b

C2c

C3a

C3b

C3c

Red

Blk

Tip[A]

Grn B l k

G r n

Shield

R e d

Note: When the length of Ring[B] is being measured, the Black test lead is shorted to Green (Shield/Ground) through an internal switch thus grounding the Tip[A] conductor. The total capacitive reactance of C3 and C1 (in ohms) translated into distance (in feet or meters) represents the length of Ring[B]. Tip [A]

Ring[B] C2

Short

C1

Shield

C1

C2

Shield

35

How Mutual length is measured with the 965DSP “OPEN” Meter Lo-Hi Frequency Sweep

Ring[B]

C1a

C1b

C1c

C2a

C2b

C2c

C3a

C3b

C3c

Red

Blk

Tip[A]

Grn B l k

G r n

R e d

Shield

Note: ‘Mutual’length is measured between ‘Tip [A]’and ‘Ring[B]’with all the test leads floating.Also take note that‘C1’and ‘C3’ are connected in series through the cable shield and then in parallel to‘C2’. The ‘Mutual’capacitance will then be ‘C2’plus the series capacitances of ‘C1’and ‘C3’. Tip [A]

Ring[B] C2

C3

C1

Cable Shield 36

Categories & Types Of Cable Faults

A. Resistance Faults: 1. Ground 2. Short 3. Cross 4. Battery Cross

B. Capacitance Faults: 1. Complete Open 2. Partial Open 3. Dirty Open 4. Split 37

A: Resistance Faults

Tip [A] Solid Ground Fault

1. GROUND : A fault between ‘Tip [A]’and ‘Ground’, ‘Ring [B]’and ‘Ground’or both conductors and ‘Ground’.

Ring [B]

OR Water

Shield Ground Fault

Tip [A] Ring [B]

Solid Ground Fault Ground Fault due to water Shield

Shield

Schematic diagram

Schematic diagram

Tip [A]

2. SHORT : A fault between ‘Tip [A]’and ‘Ring [B]’ conductors.

Water

OR Ring [B] Short due to water Solid

Short

Schematic diagram

Schematic diagram

38

Resistance Faults ( con’t ) Pair # 1 - Non-working

3. CROSS : A fault between a non-working (pair under test) and another or other nonworking pairs.

Tip [A] Ring [B] Solid

OR

Cross Fault

Water

Ring [B] Tip [A] Pair # 2 - Non-working

Note: To locate a ‘CROSS’, the pairs involved must be identified, initially.

Tip [A] Pair # 1 - Non-working Ring [B] Solid

Cross Fault

Resistive Cross fault

due to water

Ring [B] Pair # 2 - Non-working Tip [A] Schematic diagram

4. Battery CROSS : A fault between a working pair and a non-working pair (pair under test).

Pair # 1 - Working pair Pair # 1 - Working pair Tip [A]

Note:

Ring [B]

a) To locate a ‘Battery CROSS’, there is no need to identify the working pair. The fault locate procedure is the same as locating a ‘GROUND’due to the battery’s internal resistance to ‘GROUND’

Ring [B]

b) In a ‘Solid Cross Fault’, the voltage reading on the pair under test is quite high (the same or very close to the CO battery voltage) while in a ‘Non-solid Cross Fault’the voltage reading is very much lower.

Ring [B]

-48 VDC -48 VDC Solid

OR

Cross Fault

Water

-46 VDC -7 VDC

Tip [A] Pair # 2 - Non-working (Pair under test)

Resistive Cross fault

Tip [A] Pair # 1 - Working pair Solid Ring [B] Tip [A]

-48 VDC

Cross Fault

Pair # 2 - Non-working (Pair under test)

-48 VDC

OR -46 VDC

Resistive Cross fault

due to water

-7 VDC

Schematic diagram

39

B: Capacitance Faults 1. Complete OPEN: A fault where a conductor is cut off completely.

Tip [A] Complete Open Ring [B]

Tip [A] Complete Open Ring [B] Schematic diagram

Partial Open

2. Partial OPEN: A fault where a high resistance path developed on a conductor. ( Ex. Corroding splice)

Tip [A] Water Ring [B]

Partial Open Tip [A] Ring [B] Schematic diagram

40

B: Capacitance Faults (con’t) A: Complete OPEN and a SHORT

D: Partial OPEN and a SHORT

Tip [A]

3. Dirty OPEN:

Tip [A] Ring [B]

Water

Any combination of a ‘RESISTANCE’and ‘CAPACITANCE’faults

Ring [B] Tip [A] Short

Open

Tip [A] Short

Ring [B] Schematic diagram

Ring [B]

Partial Open Schematic diagram

B: Complete OPEN and a GROUND E: Partial OPEN and a GROUND

Tip [A] Ring [B]

Ring [B]

Water

Tip [A] Water

Ground Tip [A] Complete Open Partial Open

Ring [B] Ground Schematic diagram

C: Complete OPEN and a CROSS

Ring [B] Partial Open Tip [A] Ground

Pair # 1

Schematic diagram Pair # 2

Pair # 1 Cross

Complete Open

Pair # 2 Schematic diagram

41

B: Capacitance Faults (con’t) 4. SPLIT: A splicing error where one conductor of a pair (normally ‘Tip [A]’because they the same color) is spliced to ‘Tip [A]’ of another pair.

Ring [B] Pair # 1 Tip [A] Tip [A] Pair # 2 Ring [B]

Ring [B] Pair # 1 Tip [A] Split Tip [A] Pair # 2 Ring [B] Schematic diagram

42

Cable Fault-Locating Procedure 1. Fault Analysis: - Analyze symptoms carefully. - Determine the category and type of fault or faults.

2. Fault Locate to a Cable Section: - Determine the faulted cable section and isolate other sections without fault. - From a measured fault location, always consider the nearest access point (Splice, X-Connect box, or a Terminal) as the prime suspect.

3. Fault Locate (Pinpoint). - Determine the exact physical length of the cable section under test and calibrate the test set to that length. (i. e. If the section length is 500 feet or meters, select “DTS (Distance-To-Strap) Known” in RFL Setup and enter this length). - Use a separate good pair, as much as possible. Note: For short cable sections it is better to run your own “good pair” using a roll of MDF jumper wire rather than look for one in the cable.

4. Repair or Fix the Fault or Faults. 5. Verify that the line works. 43

Cable Fault Analysis Procedure 1. Check and Measure possible Voltages (AC & DC) on the line: a) between Tip[A] and Ring[B] b) between Ring[B] and Ground c) between Tip[A] and Ground 2. Check and Measure Insulation (Leakages) Resistances a) between Tip[A] and Ring[B] b) between Ring[B] and Ground c) between Tip[A] and Ground 3. With the OPENS Meter, check the capacitance lengths of Tip[A] & Ring[B] and compare. The lengths should be equal or within 10% of each other. 4. Perform a Resistance Balance Test using the Ohmmeter or Special Resistance Test in the Tool Box. a) Strap Tip[A] and Ring[B] to Shield/Ground at the far-end. b) Measure Tip[A] to Shield/Ground Resistance. c) Measure Ring[B] to Shield/Ground Resistance. d) Measure Loop Resistance (Tip[A] + Ring[B] ohms) Note: Measurements (b) and (c) should be equal or within 10% , otherwise an “open” or a “partial open” exists. 44

Factors that can cause errors in fault locate measurements 1. Poor Connections will affect RFL measurements. a) Test Leads b) Strap Note: A 1/4 (0.25) ohm resistance introduced into a 22AWG (0.61mm) conductor will constitute and error of about 16 feet (5 meters).

2. Incorrect assumption of conductor gauge (size) will affect RFL measurements. A one gauge higher or lower assumption will result into a 40% to 50% error.

3. In equalities of conductor resistances will affect RFL measurements. a) Variations of gauge created during the cable manufacturing process. b) Unequal twisting of pairs. c) Resistances introduces by connectors used during splicing. d) Inequalities of temperature along the cable length.

4. Random distribution of moisture or water in the cable will affect OPEN measurements. 5. Induced currents (from Power lines, lighting and traction circuits) during the fault locate process will affect both RFL and OPEN measurements.

45

CRAFTSMAN’S GOLDEN RULE

95% OF ALL TELEPHONE CABLE FAULTS ARE LOCATED IN AN ACCESS POINT (ex: Splices, Terminals, Cross-Connect or Protector Boxes, etc.) THE OTHER

5% CAN BE IN MID-SPAN. This means that the access point closest to the fault locate measurement must be checked first before considering the fault to be in mid-span. 46

CABLE FAULT LOCATING

? It is “NOT” an “EXACT SCIENCE”. ? It is an “ART”. ? The name of the game is “SKILL”.

47

Fault Analysis Sheet 1 (Use for Fault Diagnostics) 1. Insulation Test: Use this test to determine possible Resistance Faults like a SHORT, GROUND, CROSS or BATTERY CROSS. Tip[A] Black

Red

Black

Red

Ring[B]

Cable Shield / Ground Green Green

Note: Leave the far-end open (do not strap). Connect the test leads as shown above. Press the OHMS key and write down the resistance readings between the following: Tip[A] / Ring[B] =________________ Ohms Ring[B] / Ground = ________________Ohms Tip[A] / Ground

=________________ Ohms

A reading of 3.3 Meg-Ohms or less is will affect service which can trigger a formal complaint from the Subscriber. To avoid the customer initiating a complaint, it is suggested that the fault must be located and fixed before the fault value goes down to 3.3Meg. At this same time, since a Capacitance Balance Test does not require putting a far-end strap, the same hookup above can be used to check for possible OPEN faults using an OPEN Meter. Tip[A] Length___________feet. Ring[B] Length ____________feet.

Mutual Length _____________feet. 48

Fault Analysis Sheet 2 (Use for Fault Diagnostics) 2. Resistance-Balance Test: This test is used to determine possible existence of Capacitance Faults on a pair, like a COMPLETE OPEN, PARTIAL OPEN or DIRTY OPEN.

Tip[A] Black

Black Strap

Red

Red

Green

Ring[B]

Cable Shield / Ground

Note: In this test, the continuity of conductors TIP[A] and RING [B] are measured and compared using Shield/Ground as a reference. This is to check for possible opens on the pair, like COMPLETE OPEN, PARTIAL OPEN, or DIRTY OPEN. Strap the far-end and connect the test leads, as shown above. Press the OHMS key and write down the resistance reading between the following: Tip[A] / Ring[B] =________________ Ohms Ring[B] / Ground = ________________Ohms Tip[A] / Ground

=________________ Ohms

If Tip[A] to Shield/Ground and Ring[B] to Shield/Ground resistances differ by 10% or more, an OPEN exists on the pair. 49

50

Resistance Fault Locate (RFL) Hookups Option A: Using a Separate Good Pair

1. Ground: Green

Separate Good Pair

Yellow Strap Ring[B] Pair Under Test Red

Tip[A] Ground

965DSP Black

Fault

Shield / Ground

Option B: Single Pair (Single Good Conductor) Ring[B] - Good Conductor Green Strap Red

Tip[A] Ground

Black

Fault

Shield / Ground

965DSP

51

Resistance Fault Locate (RFL) Hookups (con’t) Option A: Using a Separate Good Pair

2. Short:

Green Good Pair

Yellow Strap Ring[B] Red Short

965DSP Black

Tip[A]

Option B: Single Pair (Single Good Conductor)

Good conductor Green Strap

Red

Tip[A] Short

Black

Ring[B]

965DSP 52

Resistance Fault Locate (RFL) Hookups (con’t) Option A: Using a Separate Good Pair

3. Cross: Green Good Pair

Yellow Strap

Ring[B] Pair Under Test [Non-Working] Tip[A] Red

965DSP

Cross

Black

Ring[B] Other Pair [Non-Working] Tip[A]

Option B: Ring [B] conductors of each pair used as a GOOD pair if they are clean (no faults).

Green

Ring[B] - Good Conductor Tip[A] Strap

Red Cross

Black

Strap

Tip[A] Ring[B] - Good Conductor

965DSP Yellow

53

Resistance Fault Locate (RFL) Hookups (con’t)

C. Cross:

Option C: Using a Single Good Conductor

Good conductor Green

Tip[A] Pair Under Test - Non-Working

Strap

Ring[B] Red Cross

Black

965DSP

Ring[B] Other Pair - Non-Working Tip[A]

54

Resistance Fault Locate (RFL) Hookups (con’t)

4. Battery Cross: Option A: Separate Good Pair Green

Tip[A] Strap

Good Pair

965DSP

Ring[B] Yellow

Red

Tip[A] Pair Under Test [Non-Working] Ring[B]

(

)

-48VDC Battery Cross

CO Battery

Ring[B] Other Pair - Working (Unknown) Tip[A]

(

) Black

Shield / Ground

Note: The Tip[A] conductors from each pair can be used used as the GOOD pair.

55

Resistance Fault Locate (RFL) Hookups (con’t)

4. Battery Cross: Option B: Single Good Conductor 965DSP

Good Conductor Green

Tip[A]

Red

Ring[B]

Pair Under Test - Non-Working

(

Strap

) Battery Cross

Ring[B] Other Pair - Working (Unknown) Tip[A]

(

) Black

Shield / Ground

-48VDC CO Battery

Note: Use this option if only one GOOD conductor is available.

56

RFL TIPS The use of a “Separate Good Pair” is always the most accurate way to locate any type of a resistance fault.

57

“Separate Good Pair” It can be any pair of any gauge, longer or shorter than the faulted one, it doesn’t matter. For short cable section lengths (1000 feet or less), the good pair can be a reel of a CO jumper wire or a telephone jacketed wire placed above ground. Reel of CO jumper wire

End-2

or Good Pair

telephone jacketed wire

End-1

Good Pair

Strap

Faulted Pair

Ground

Near-End

Shield/Ground

Fault

Far-End

58

“Separate Good Pair” It can be any pair of any gauge, longer or shorter than the faulted one, it doesn’t matter. For long cable section lengths (several thousand feet), the good pair can come from another cable adjacent to the cable with the faulted pair. End-2 Good Pair

Good Pair End-1

Strap Fault Common Faulted Pair Faulted Pair

Short Near-End

Far-End

59

How To Extend The “Far-End Strap” If Necessary Reel of CO jumper wire or telephone jacketed wire or any two wires, same length (any gauge)

Good Pair [ from a distant cable ]

Strap extension

End-1

End-2

Far-End Strap

Faulted Pair Near-End

Short

Common

Far-End

60

Fault Locating Tips RFL (Resistance Fault Locate): 1. Always draw a diagram of the fault for better analysis. 2 . There three factors that is always involved in RFL (Resistance Fault Locating) - Gauge, Length and Temperature of the cable. Any two of the three must be known for RFL to work. The best option is to know the Gauge and Length of the section under test and the test set will compute the cable temperature. This is done during RFL Setup. 3. A pair may have some light faults in it but it can be used as a ‘Good Pair’as long as the light fault is at least 200 times better than the magnitude of the fault in the faulted pair. Ex: If the fault on a pair is 1 kilo-ohms, a pair with a 200 kilo-ohm fault can be used as a good pair. Of course, the higher the magnitude, the better. 4. For best RFL accuracy , make a long cable section shorter by going to the middle of the section and open the pair to cut it in half. Check for the fault in one direction and then the other and then isolate the clean side. Repeat the process until the cable section becomes short enough where the following becomes practical: a) the length of a short section can easily be measured physically with a roller tape. If gauge and section length are known, the test set will compute cable temperature. b) With a short cable section, the use of a reel of jumper wire as a “Good Pair” placed above ground is now possible, instead of digging into the cable for a good one. Saves time. With a separate good pair and knowing the gauge and length of the section is the best and most accurate RFL option. 5. The procedure in locating a ‘Battery Cross’is exactly the same as that for a ‘Ground’ fault. 6. In a ‘Single Pair Hookup’, the best good conductor to use is the mate of the faulted one and the next best is any good conductor from any of the adjacent pairs in the same group. Ex: If a pair has TIP(A) is faulted and RING(B) is good, RING(B) is then the best good conductor to use to shoot the fault on TIP(A). 7. If DTF (Distance-To-Fault) and DTS (Distance-To-Strap) are equal, the fault is either at the strap or beyond. 61

Estimating Cable Temperatures

Aerial Cable: 1. If cable is not in direct sunlight. Add 20oF or 15oC whichever is used, to the air temperature. 2. If cable is in direct sunlight. Add 40oF or 30oC whichever is used, to the air temperature.

Buried Cable: 1. Use temperature of tap water. Let water flow out of a water faucet for several minutes and then measure the temperature using a common household thermometer. 2. In cold climates, use soil temperature at cable depth. 62

Gauge (Size) Conversion Table FROM GAUGE

TO GAUGE

MULTIPLY BY

19 ----

22 24 26 28

0.497 0.310 0.193 0.121

22 ----

19 24 26 28

2.010 0.624 0.389 0.244

24 ----

19 22 26 28

3.220 1.600 0.623 0.391

26 ----

19 22 24 28

5.180 2.570 1.610 0.628

28 ----

19 22 24 26

8.240 4.090 2.560 1.590

Example: Convert the following into 19AWG. 400 feet of 24AWG + 350 feet of 22AWG + 800 feet of 19AWG

400 x 3.220 = 1,288 feet of 19AWG 350 x 2.010 =

703 feet of 19AWG

800 x 1.000 =

800 feet of 19AWG

-------------------------------------------Total

= 2,791 feet of 19AWG

63

How To Determine Length of Cable In A Reel - Using RFL Option #1: 1. Create a “SHORT” at the far-end of Pair #2 and strap it to Pair #1 (Good Pair) and connect the 965DSP clips as shown below. 2. Press the RFL key and do the following: a) Select “Separate Pair” option. b) Press the “Tab” key : - Highlight the correct gauge (size) of the pair. - Press the ‘Select’key and enter cable temperature (ex: 70 oF) 3. Press the ‘Enter’ key to accept options. 4. Press the ‘Enter’ key to continue. 5. The DTF (Distance -To-Fault) or DTS (Distance-To- Strap) measurement will be the length of the cable.

Tip [A] Green Pair #1 - Good Yellow

Ring [B] Strap Tip [A]

Red

DynatelTM 965DSP

Black

Pair #2

Short

Ring [B]

Reel of Cable

64

How To Determine Length of Cable In A Reel - Using RFL

Option #2: 1. Press the RFL key. 2. Short the pair at the far-end and connect the 965DSP test clips, as shown below. 3. Press the ‘Tab’ key to select ‘Single Pair’. 4. Press the ‘Setup’ key and do the following: a) Highlight the correct gauge (size) of the pair. c) Press the ‘Tab’ key and enter cable temperature (ex: 70 oF). 5. Press the ‘Enter’ key to accept the options. 6. Press the ‘Enter’ key to continue 4. The DTS (Distance-To-Strap) reading will be the length of the cable.

Red Tip [A] Black Green

Short Ring [B]

DynatelTM 965DSP

Reel of Cable

65

Measuring Distance To A Solid Short - Using RFL Note: This procedure only applies to a solid “short”, meaning (0 ohm- resistance), otherwise use the standard RFL procedure using a separate good pair or a single good conductor. 1. Connect the 965DSP test clips, as shown below. 2. Press the RFL key. 3. Press the ‘Tab’ key to select ‘Single Pair’. 4. Press the ‘Setup’key and do the following: a) Highlight the correct gauge (size) of the pair. c) Press the ‘Tab’key and enter cable temperature (ex: 70 oF). 5. Press the ‘Enter’ key to accept the options. 6. Press the ‘Enter’ key to continue 4. The DTS (Distance-To-Strap) reading will be the location of the solid short.

Solid SHORT (0-ohm) Red

Tip [A]

Black Green

Ring [B]

DynatelTM 965DSP

66

Fault Locating Tips OPENS Locate: 1. Make sure the ‘GREEN’clip is connected to the cable shield (ground) when locating opens. 2. Cable ‘gauge and temperature’will not affect cable capacitance. 3. For accuracy, always calibrate the test set to a good pair in the same cable as the faulted one. 4. ‘OPENS’Locate does not require a strap. Use it first when analyzing cable faults. 5. If ‘MUTUAL’measurement is 10% or more longer than Tip [A] or Ring [B], the cable shield can be open due to a missing bond, corroded bond connections or it went open due to extreme cable temperature changes.

TDR (Time Domain Reflectometer): In most cases, a TDR (Time Domain Reflectometer) which uses RADAR technology is a better test set to use for locating any type of OPENS [Complete Open, Partial (high-resistance) Open or Dirty Open (a combination of resistance and capacitance faults)]. But never use a TDR when you do not exactly know what type of fault/faults or line treatment devices (load coils, build-out capacitors) you are looking for.

67

Metric Conversion Table

Metric Unit

Metric Length

Approximate U.S. Equivalent

Metric (m)

1.0 m

39.4 inches

Millimeter (mm)

.001 m

.0384 inches

Micrometer (um)

.000 001 m

.000 0394 inches

Nanometer (nm)

.000 000 001 m

.000 000 0394 inches

Angstrom (A)

.000 000 000 1 m

.000 000 00394 inches

68

POWERS OF TEN Prefixes and symbols to form decimal multiples and/or submultiples. Power

E

Decimal

Prefix

Phonic

of Ten

Notation

Equivalent

1012

E + 12

109

Symbol

1 000 000 000 000

tera

ter’a

T

E + 09

1 000 000 000

giga

gi’ga

G

106

E + 06

1 000 000

mega

meg’a

M

103

E + 03

1 000

kilo

kil’o

k

102

E + 02

100

hecto

hek’to

h

10

E + 01

10

deka

dek’a

da

10-1

E-01

0.1

deci

des’i

d

10-2

E-02

0.01

centi

sen’ti

c

10-3

E-03

0.001

milli

mil’I

m

10-6

E-06

0. 000 001

micro

mi’kro

u

10-9

E-09

0.000 000 001

nano

nan’o

n

10-12

E-12

0.000 000 000 001

pico

pe’ko

p

10-15

E-15

0.000 000 000 000 001

femto

fem’to

f

10-18

E-18

0.000 000 000 000 000 001

atto

at’to

a 69

Locating OPENS by Ratio

Requirement: Length of cable section under test must be known. Procedure: 1. Connect the test set as shown in the illustration and make the “A” measurement.

Measuring distance to an open using cable SHIELD as reference.

2. Move the test set to the far-end and make the “B” measurement. 965DSP “A” measurement

“D” measurement

3. Calculate distance to the open using the formula, below: d = (A or B) x D meters to open

OPEN

C Cable Shield

Where: 965DSP

“D” measurement “B” measurement

d = Distance-To-Open (A or B) means whichever is shorter. D = Length of cable section under test. C = A+B

OPEN

Cable Shield

Example: D = 290 m

Note: The RED and GREEN leads are used so consider the Ring [B] measurement only.

A = 110 m B = 240 m C = A + B = 110 + 240 = 350 m d = A x D = 110 x 290 = 91.14 m C

350 70

Locating OPENS by Ratio Measuring distance to an open shield using Earth/Soil as reference.

965DSP

Red Grn

Ground Rod

Cable Shield

Earth/Soil

OPEN

Cable Shield

“A” measurement “D” measurement

Note: The RED and GREEN leads are used so consider the Ring [B] only.

measurement

965DSP

Red Grn

Ground Rod

Earth/Soil

Cable Shield

OPEN

Cable Shield

“B” measurement “D” measurement

71

Locating OPENS by Ratio

Measuring distance to an open shield using a group of conductors as reference. “D” measurement “A” measurement Open

965SLA

“D” measurement “B” measurement Open

965SLA

Note: The RED and GREEN leads are used, consider the Ring [B] measurement only.

72

Dynatel 965DSP Subscriber Loop Testing & Analysis

73

Subscriber Loop Components Central Office

Protector

48VDC

Distribution Cable

Fig. 1: Standard Telephone Circuit

Telephone Set

Protector

REG Protector 30VDC 48VDC

78VDC

Distribution Cable

Telephone Set

Central Office Protector

Fig. 2: Telephone Circuit with REG (Range Extender with Gain). 74

Why analyze a Subscriber Loop? A: To evaluate a cable pair before it is put into service. Generally Accepted Criteria for POTS (Plain Old Telephone Service) ________________________________________________________________________________________________________________ Parameter

Acceptable

Marginal

Unacceptable

________________________________________________________________________________________________________________ Voltage

=

48 to 52VDC

_________________

_______________

Loop Current

=

-23 mA or more

-20 mA to -8.5 dBm

Power Influence

=

80 dBrnC or less

> -80 dBrnC to < -90 dBrnC

-90 dBrnC or more

Circuit Noise

=

20 dBrnC

> 20 dBrnC to < 30 dBrnC

-30 dBrnC or more

Balance

=

60 dB

> 50 dB to < 60 dB

50 dB or less

Station Ground Resistance =

25 ohms or less

_________________

> 25 ohms

Slope

7.5 dB or less

_________________

> 7.5 dB

=

________________________________________________________________________________________________________________ Parameter

Insulation Good

Light Fault

Heavy Fault

(Service Affected)

(Out Of Service)

________________________________________________________________________________________________________________ Insulation Resistance

3.3 Meg or more

> 2.8 K ohms to < 3.3 Meg

2.8 K ohms or less

75

Why analyze a Subscriber Loop?

B: To identify and isolate the cause of a problem on a partially working cable pair.. Common Subscriber complaints: 1. No dial tone. 2. Continuous dial tone. 3. Signal is too weak can not hear on long distance calls. 4. Occasionally get wrong numbers. 5. Line is too noisy.

76

Resistance Zones and CO Equipment

RZ13

RZ16

RZ18

RZ28

CO

15Kft (4,572m) Loading

required

1300 Ohms

1540 Ohms

2000 Ohms

2800 Ohms

37Kft (11,278m)

44Kft (13,411m)

56Kft (17,069m)

79Kft (24,079m)

2A RE (Range Extender)

DLL + E6 Repeater or 5A or 7A REG (Range Extender with Gain)

DLL + E6 Repeater or 5A or 7A REG (Range Extender with Gain)

Note: This example shows distances of the RZs based on a 22AWG (0.64mm) cable. If the Engineers undergauge, RZ18 could start as close as 18Kft. (5,486m).

77

Transmission

Resistance Design

Long Route Design 1300 ohms

Main Distribution Frame

Customer Line Equipment

5A or 7A REG

2000 ohms

2800 ohms

RZ13

CO

2A RE

1540 ohms

RZ16

RZ18

RZ28 5A or 7A REG

78

Load Coil Construction Coil Sales 662

88 MH

309 79

Tip[A]

Tip[A]

Ring[B]

Ring[B]

Tip[A]

IN

Tip[A]

OUT Ring[B]

Hundreds of turns of fine magnet wire

Ring[B] Torroid (Doughnut)-shaped iron/nickel core

A Load Coil is used to cancel out the effects of too much capacitance on the pair as it gets longer so that voice frequency signals can be transmitted at longer distances (ie: 18000 to 34000 feet)

79

Load Coil Schemes

Loading System B-44 D-66 H88

Bandwidth

Cutoff Frequency

Inductance

Spacing

2400 Hz 3100 Hz 4500 Hz

6943 Hz 4629 Hz 3471 Hz

44 mH 66 mH 88 mH

3000 Ft 4500 Ft 6000 Ft

80

Resistance Design Examples 14.5Kft (4,420m) 1300 ohms 14,500Ft. (4,420m)

26AWG (0.41mm)

CO

9Kft (2,743m) 26AWG (0.41mm)

CO

3Kft (914m)

1

6Kft (1,829m)

9Kft (2,743m) 24AWG (0.51mm) 2

6Kft (1,829m)

1300 ohms 18,000Ft. (5,486m)

3Kft (914m)

3

Load Coils 22Kft (6,706m) 24AWG (0.51mm)

CO 3Kft (914m)

CO

CO

1

6Kft (1,829m)

2

6Kft (1,829m)

3

1300 ohms 22,000Ft. (6,706m)

6Kft (1,829m)

13Kft (3,962m) 24AWG (0.51mm) 3Kft (914m)

1

6Kft (1,829m)

4

1Kft (305m)

15Kft (4,572m) 22AWG (0.64mm) 2

4Kft + 2Kft (1,219m + 610m)

3

6Kft (1,829m)

4

1300 ohms 28,000Ft. (8,534m)

7Kft (2,134m)

34Kft (10,363m) 22AWG (0.64mm) 3Kft (914m)

1

6Kft (1,829m)

2

6Kft (1,829m)

3

6Kft (1,829m)

1300 ohms 34,000Ft. (10,363m) 4

6Kft (1,829m)

5

7Kft (2,134m)

81

Build Outs Cable build outs are primarily designed to make cable pairs electrically longer when cable sections are physically too short. Build Out Configurations 1. Build Out Capacitor [BOC] - it is used when the length of cable section is more than half of the cable spacing required. (ie: H-88 coils require 6000 feet of cable spacing. If the cable section is more than 3000 feet but less then 6000 feet, a build out capacitor [BOC] must be used. Lake or Riverbed

Physical length 3000 Ft

4750 Ft 6000 Ft

CO

BOC

Load Coil

Load Coil

6000 Ft Electrical length

2. Build Out Lattice [BOL] - it is used when the length of the cable section is less than half of the cable spacing required. (ie: if the cable section is less than 3000 feet). Lake or Riverbed

Physical length 3000 Ft

1700 Ft 6000 Ft

R

CO

Load Coil

C

BOL

Load Coil

6000 Ft Electrical length

82

How to compute the equivalent length of build-out capacitor and subtract it from Distance To Open measurements Standard Tip[A] or Ring [B] to Shield/Ground Capacitances Aircore

=

0.125uf / mile (5280 feet)

Jelly-Filled

=

0.140uf / mile (5280 feet)

2-Pair Drop

=

0.155uf / mile (5280 feet)

5-Pair Drop

=

0.150uf / mile (5280 feet)

Example: Ring is open at 7000 feet Aircore (Tip[A] /Ring[B] to Shield /Ground capacitances

=

0.125 uf / 5280 feet

0.125uF / 5280 feet

=

0.000024 uF / feet

0.000024 uF x 1000

=

0.024uF / 1000 feet

=

0.0314 uF

0.0314 uF / 0.024 uF

=

1.308

1.308 x 1000 feet

=

1308 feet (equivalent length of build-out

Build-Out capacitor across Tip[A] & Ring[B]

capacitor) Distance to Open on Ring [B]

=

7000 feet - 1308 feet = 5692 feet

83

Noise and Power Influence Measurements 965DSP Red Quiet Termination

Grn

600 ohms

2 uF

Blk Fig. 1:Circuit Noise (Noise Metallic) is measured between Tip[A] & Ring[B]

965DSP Red

Grn

Quiet Termination

600 ohms

2 uF

Blk Fig. 2: Power Influence is measured between Tip[A] & Ring[B] (shorted together internally) and Shield/Ground Blk

Red

84

Circuit Noise Basics IP - Current flowing through the power line. IT - Induced current on the Tip[A] conductor from the power line. IR - Induced current into the Ring[B] conductor from the power line.

IP

Power Line

Magnetic Field

Central Office Tip[A] 600 ohms

2 uF

Quiet Termination

IT Telephone Set

Ring[B]

IR

Power induction parameters: 1. Influence - depends on power utility load; therefore it varies during the day. 2. Coupling - depends on the length of exposure and separation between Telco and Power utility. 3. Susceptibility - depends on cable pair balance, shield continuity and low resistance grounds. If the pair is well-balanced, IT and IR will be equal and self-cancellation occurs and Noise = 0. Note: 1 & 2 above, usually are beyond the control of the Telco and rarely can they do anything about them. 85

Circuit Noise Basics (con’t) IP - Current flowing through the power line. ISP - Induced current on the cable shield from the power line. IT - Induced current on the Tip[A] conductor from the power line. IR - Induced current into the Ring[B] conductor from the power line. ITS - Induced current on the Tip[A] conductor from the cable shield. IRS - Induced current on the Ring [B] conductor from the cable shield.

Power Line

Shield/Ground

Power Line Magnetic Field

IP

Shield Magnetic Field

ISP Tip[A]

600 ohms

2 uF

Quiet Termination

ITS

IT Telephone Set

IRS

IR

Ring[B]

Central Office Note: 1. If the pair is well balanced, the opposing currents IT vs IR and ITS vs IRS will be equal and therefore cancel out. 2. A perfectly balanced pair can be noise-free even without a cable shield. 3. A good shield continuity and low resistance grounds can reduce Power Influence by 15dBrnC. 86

Relationship between dBrnC and dBm Noise dBrnC Very Noisy

dBrnC =

dB reference to noise with C-Message Weighting

Very Quiet

Signal Level dBm

90

0

80

-10

70

-20

60

-30

50

-40

40

-50

30

-60

20

-70

10

-80

0

-90

dBm =

dB reference to milliwatt

Note:

dBm - dBm = dB

Very Weak 87

3M Training Center Telephone Numbers Line Assignments: Left Side:

Right Side:

1.

9-984-2983

5.

9-984-2966

2.

9-884-2974

6.

9-984-2977

3.

9-984-2966

7.

9-984-2978

4.

9-984-2988

8.

9-984-2979

3M 1020B Access Numbers - Training Room: 1.

9-984-2036

6.

9-984-2048

2.

9-984-2040

7.

9-984-2052

3.

9-984-2041

8.

9-984-2975

4.

9-984-2041

9.

9-418-1458 (10 Frequency Step Tone 1004Hz, 404Hz,

5.

9-984-2047

650Hz, 1004Hz, 1300Hz, 1704Hz, 2000Hz, 2300Hz, 2804, 3000Hz, 5000Hz) then disconnect. Duration per frequency is 5 seconds with 1 second quiet intervals. All frequencies are transmitted @ 0 dBm.)

Southwestern Bell Telephone Company Milliwatt Tone Sources (1004 Hz.): Jollyville C.O.

9-258-1632

Evergreen C.O.

9-474-8800

Fireside C.O.

9-345-1217

9-258-9827

Evergreen C.O.

9-474-8801

Fireside C.O.

9-345-1212

Quiet Line: Jollyville C.O.

ANA (Automatic Number Announcer):

9-830

NYNEX Programmable Test Line (18- Frequency Tone Source) *8-518-435-2332 When initial 1004Hz tone stops, press 5 to switch source from Milliwatt to 17 frequency Step Tone - 304Hz, 404Hz, 604Hz, 804Hz, 1004Hz, 1204Hz,1404Hz, 1604Hz, 1804Hz, 2004Hz, 2204Hz, 2404Hz, 2604Hz, 2804Hz, 3004Hz, 32004Hz, 3404Hz. Press *5 to set tone levels at 0 dBm at the C.O. 88