3M CablePipe Locating Techniques Manual

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4. Applying Signal to Telephone Cable: Dyna-Coupler Method
4.1 The Dyna-Coupler puts signal selectively on a cable by clamping around it.  This eliminates the
need to disconnect the cable.  Do not use the Dyna-Coupler on a cable that has the shield
ungrounded at both ends.
4.2 Place the Dyna-Coupler on the cable between
the ground bonding and the point where the
cable enters the earth as shown (A).  Note
that if you place the Dyna-Coupler above the
bond, the signal travels to ground, and not
onto the cable.
Note: Always use the high output level when using the coupler. 4.3 On short cables, such as service drops, do
not use the Dyna-Coupler on an ungrounded
end (C). It works better on the grounded end
(D). If possible, ground end (C); if not, be
sure to use the highest frequency possible. 
						

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4.4 If the cable is long, remove the bonding
and signal goes both ways as shown.
4.6 Several cables grounded at a common
point present no problem for the Dyna-
Coupler method. Even though signal is
coupled into each cable, the cable with
the Dyna-Coupler is clearly
identifiable because it has the strongest
signal. 4.5 Clamping the Dyna-Coupler to a cable
with drop lines or laterals puts full
signal on the cable until the junction
point. The signal may split evenly at
the lateral as shown. When tracing, the
speaker volume and signal level
indication drops when the Receiver
passes the junction.  This is an easy
way to find laterals. 
						

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5. Locating Slack Loops and Butt Splices
5.1 To identify the presence of a slack loop or
butt splice in a cable path, first locate and
mark the cable path.
5.2 Find the strongest response over the marked
cable path and reset the gain.
5.3 Retrace the cable path with the Receiver
held so the handle is perpendicular to
(across) the cable path, as shown. When the
Receiver passes over a slack loop or butt
splice, the signal increases and the bar graph
closes. Mark each response. Whenever you
encounter such a condition, check to see if
an unknown lateral exists.
6. Locating Unknown Laterals
6.1 To check for unknown laterals which may
radiate from a butt splice type or closure, first
trace and mark the cable path.  Retrace to
locate any butt splices or slack loops. Mark
the spot of any detected butt splices or slack
loops.
 6.2 If the Receiver gain has not been set while
performing the normal trace, go to the marked
trace path and pinpoint the path. Reset the
gain.
6.3 Walk 10 to 25 feet off the trace path and away
from the marked butt splice or slack loop.
Hold the Receiver so that the display end of
the handle points directly to the mark. Walk in
a circle around the mark with the Receiver
handle pointing to the mark.
6.4 The Receiver remains relatively quiet until it
crosses a lateral or the actual cable path.
Since there could be several laterals radiating
from the closure, mark each occurrence of
signal around the circle.  After you locate each
lateral, trace and mark its path. 
						

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7. Locating Cables from Pedestals
7.1 To locate a single cable path from a pedestal, follow these steps:
7.2 At the pedestal, apply tracing signal on the target cable using the Dyna-Coupler method.  If the
header in the pedestal is not grounded, use the ground rod and ground extension cable to ground
it.
7.3 Walk 10 to 25 feet away from the pedestal.  Hold the Receiver so that the display end of the
handle points directly to the pedestal.  Start walking in a circle around the pedestal with the
Receiver always pointing toward the pedestal.
7.4 The Receiver remains relatively quiet until it crosses a cable.  Stop when there is a response.  Find
the point of strongest signal and press gain. Check the numeric display for relative signal strength.
Remember the number and continue walking the circle. As you walk away from the cable, the
signal drops. Press gain and continue. When you encounter another response, find the point of
strongest signal. If the greatest signal strength is more than 25 points higher than the others (if any
found), then that is the target cable.  If the signal levels are closer, then measure the depth of each
cable found and note the bar graph in the depth mode (this is a relative measurement of the current
flowing in the cable). In the depth mode, the cable that shows at least two more segments on the
bar graph than the other cables is the target cable. 
						

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8. Locating Service Drops
8.1 When locating the path of a service drop from a house or other building, it is more convenient to
apply signal at the house or building.  Connect the Transmitter using the direct-connect method.
Use the standard tracing techniques described earlier.
9. Locating an Open End
9.1 To locate an unterminated or open end of a cable or drop, follow these steps.
9.2 If the cable is bonded to ground at the access point, connect the Transmitter using the Dyna-
Coupler method. Otherwise, if the cable is not bonded to ground at the access point, connect the
Transmitter using the Direct-connect method. With either method, choose the highest frequency
available, at high level.
9.3 Trace the cable path. The receiverÕs response decreases suddenly at the site of the clear or severed
end.
10. Identifying Cables
10.1 This procedure identifies a single cable in a group of similar cables. At an access where cable
identity is known, use the Transmitter to put signal on the sought cable with the Dyna-Coupler.
Select the highest frequency available.  Output level should be set to high.  It is not necessary to
remove any bonds or ground. At an access at the far-end of the cable group, connect another
Dyna-Coupler to the Receiver with the Extension Cable. On the Receiver, select the PEAK trace
mode.  Select the same frequency as the Transmitter. Check the first cable in the group by
clamping the Dyna-Coupler around the cable.  Press the GAIN ADJUST key and observe the
numeric display, which is relative signal strength.  Remember the number and continue by
clamping the Dyna-Coupler around the next cable in the group.  If the signal strength is greater
than the previous observation, press the GAIN ADJUST key.  If the signal strength is less than
before, ignore it.  After checking all the cables in the group, the cable with the highest reading is
the one being sought. 
						

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11. Pair Identification
11.1 This procedure identifies individual conductors within the same cable.  It uses the Dyna-Coupler,
so none of the pairs will need to be cut.  The use of the high frequency will also allow tagging of
conductors in a wet pulp section.
11.2 At a splice or access, use the Transmitter to put signal on the pair to be identified using the Dyna-
Coupler. To minimize signal canceling and disruption on active pairs, clamp the Dyna-Coupler
around both tip and ring of the pair and make sure it is fully closed.  Place the transmitter in the
tone mode and select the highest frequency. If your Transmitter does not have this feature, the
highest frequency trace mode will also work.
11.3 Take the Receiver and Inductive Probe to the location where identification is needed.  Connect the
Inductive Probe to the Receiver using the 6-ft. Probe Cable.  Both the probe and the cable are
available as optional accessories.  Select the same mode and frequency as the Transmitter.
11.4 Insert the Probe into the bundle of pairs (or the group, if known) and press the  GAIN ADJUST
key.  Next, divide the pairs into two bundles and insert the Probe into each of the bundles and
observe the numeric display.  The bundle with the highest reading will contain the sought pair.
Continue by dividing the bundle with the sought pair into two parts and checking each part for the
highest signal.  In this way the sought pair will be isolated.
Note: There is a groove around the inductive Probe to indicate the location of the sensing coil. The
coil is oriented so that maximum signal will be sensed when the probe is perpendicular to the
cable conductor. 
						

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12. Locating Splits
12.1 To locate the splice where a split occurs, attach the Transmitter to tip and ring of one pair of the
split. Strap the tips and rings of both pairs at a far-end access beyond the splice.
12.2 On the Transmitter, select the tone mode and the low frequency.
12.3 Using either the Receiver, a toning amplifier or a toning coil, detect a weak tone from the
Transmitter to the split, and strong tone from the split to the strap.
12.4 To verify that the split has been located, attach the Transmitter to a non-split conductor of one pair
and a split conductor of the other pair. The tracing tone is strong from the Transmitter to the split,
and weak from the split to the strap. 
						

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A. Can the Fiber Be Traced?
13.1 Fiber optic cables consist of fragile optical fibers encased in a strengthened outer member. The
internal sheath of the cable may or may not be metallic. If it is not metallic, the manufacturer may
include a metallic strength member (wire) within the sheath.  Some fiber optic cables have no
internal metal structure, in which case the contractor installing the cable may pull an insulated
wire through the underground duct with the fiber optic cable. If a metallic conductor is not in or
next to the fiber optic cable, you cannot trace the cable path. You must then rely on site plans for
physical location.
13.2 You normally find underground fiber optic cable installed in a duct, or a tube within the duct. The
installation is normally made from a central office to a remote terminal office or distribution point.
There may be several splice points in hand holes or manholes along the route. Installation
practices generally require that the fiber optic cable metallic sheath or strength member be
grounded at the terminating ends. Bonding practices at the splice points vary by company.
Therefore, the metallic strength member may or may not be grounded or may be grounded
through a remotely-actuated relay or a voltage transient suppression device.  Some installations
include a permanently installed rack-mounted transmitter that can selectively place a tracing
signal on one of several fiber optic cables. If this transmitter produces a 577 Hz signal, you can
trace the fiber optic cable using the Dynatel Receiver. 13. Fiber Optic Locating 
						

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B. Applying the Trace Signal
13.3 If the office installation includes a rack-mounted transmitter, check to see if your Receiver has the
same frequency.  Some Receivers will receive 512 Hz and 560 Hz as well as 577 Hz. To use the
transmitter, attach it to the sheath or strength member of the fiber optic cable to be traced and turn
it on. If the transmitter frequency does not match the Receiver, or a rack-mounted transmitter is
not available, attach the Dynatel Transmitter at the CO/Remote Terminal Office, or at an
intermediate splice point.
13.6 To attach the Transmitter at a field splice point, access the splice case.  If the splice case has one
or two metal straps connected to ground, you can attach the Transmitter at this location.
13.7 If the splice case has two straps, one of
them most likely attaches to the
metallic sheath or strength member on
the incoming side and the other strap
attaches to the outgoing side. This lets
you connect the Transmitter to the
incoming or outgoing side. The two
straps may also be connected inside
the splice case. 13.4 To attach the Transmitter at the Central
Office or Remote Terminal Office, bring it
to the location in the office where the fiber
optic cable strength member is grounded.
Typically, this is near the rack-mounted
digital conversion equipment. Locate and
disconnect the metal strength member from
the frame or rack ground point.
13.5 Check the resistance using the ohms mode.
Relatively high resistance (greater than 2 k
ohms) means there may be an open between
this connection point and the ground at the
terminating end or intermediate splice
points. If the resistance is very low (less
than 250 ohms), there may be another
ground point on the strength member within
the CO. Either condition probably causes
very little of the signal to be placed on the
fiber optic cable outside. An acceptable
condition is a resistance reading between
250 ohms and 2 k ohms.
Attaching at the Splice Point
Attaching at CO or Remote Terminal Office 
						

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13.8 Maximum tracing signal is obtained
by disconnecting the bonding
strap(s) from the ground point before
attaching the Transmitter, but local
practice may not allow this.  In this
case, the signal splits between the
incoming cable, outgoing cable, and
the ground point, thus reducing the
tracing range.
13.9 Use high level output if tracing fiber
optic cable longer than .5 miles.
C. Tracing the Fiber Optic Cable
13.10 When tracing from a CO or Remote Terminal office, move to the cableÕs expected exit point
outside the building. Select the same Receiver frequency as the Transmitter.
13.11 Search the area until the unit receives the signal.  When tracing at a manhole or hand hole, walk in
a circle around the hole with your back or front toward the hole.  Move toward increasing signal
strength, adjusting Receiver gain as needed until you locate the cable.  Trace the path of the cable.
13.12 When tracing a cable over a long distance, the signal strength decreases. This can be caused by the
signal ÒbleedingÓ off into the earth due to capacitance or by additional grounds at splice points
along the fiber optic cable. The ÒbleedingÓ effect causes a gradual reduction in signal strength as
the Receiver moves along the cable. The splice point ground causes an abrupt or distinct drop in
signal because the signal is split between the outgoing fiber optic cable and the local ground.
These intermediate ground points can severely limit the tracing distance unless you use a high-
powered Transmitter.  This abrupt drop in signal is a good indication of the presence of an earth
ground at a splice point.