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British Telecom Testing Equiptment Typed by Dosile & Psyclone
> i N D E X <
1. General Desciption
2. Description of Equiptment Items
3. Principle of Operation
4. Using the Oscillator 87G
5. Using the Amplifier 109H
6. Care and Maintenance of the Tester
1. General Desciption
a. Oscillator 87G
b. Amplifier 109H
c. Receiver Headgear 17A
d. Receiver Handgear 18A
e. Adapter Test 18A
f. Cord Connecting 2/26A
g. A storage/carrying satchel
h. This handbook
The powered items (Oscillators and Amplifier) are primary cell battery
operated units.
The Tester 132C enables cable pairs to be identified quickly in BT local
networks, provided that the pairs are in good electril condition.
Where insulation resistance is low or where pairs are subject to short
circuits, contacts or disconnections, location and identification may
bemore difficult.
The equiptment must only be used in the manner and purpose specified inthis
handbook or approved documation.
No unapproved modifications are to be made to this equiptment.
2. Description of the Equiptment Items
2.1 OSCILLATOR 87G
-General
The signal otput us provided via two 4mm sockets enabling the use of
standard leads. A moniter socket is provided to enable connection of a
suitable headphone (Reciever headgear 17A or equipvalent)
The Osciallator provideds a kHz signal output to line. This signal maybe
continuous, or interrupted at between 2 and 10 pulses. The ootput is setby
a single rotary control.
If desired, the output signal can be monitiered whilst the rate is
beingset. This is achieved by listening to a headphone connected to the
monitor socket and with the output sockets shortened (loopened) together.
-DETECTION OF LINE STATUS
The moniter headphones provides an indication of a satisfactory line
connection and also of temporary shorting of the connected line.
When the Oscillator us sending a signal to line, a low level signal willbe
heard in the headphone. The headphone output level will rise briefly (for
approximately 3 seconds) when the line is shorted along it's length. The
`SHORT' indicator will illuminate during this period. The `short' condition
may also be indicated when the line connection is first made. The
indication will depend on the line length and the Oscillator model.
NOTE :
a) When the pair is shorter than 100 meters, the indication of line
presence may not operate reliable. b) When the pair is longer than 2.5
kilometers, the shorting conditionswill not operate reliably.
-BATTERY STATE INDICATION.
A battery state indicator lamp (`BATTERY') is provided on the Oscillator.
When the Oscillator is on, this indicator will flash for approximatelyflash
for 2 second intervals. This signifies that the battery voltage is
adequate.
If the voltage falls to a level such that the battery requires replacement,
the indicator will flash at a faster rate (typically 7 times a second).In
addition, the signal output to line will change. This will give an
indication to the Amplifier operator that Oscillator battery failure is
imminent. (typically half an hour after the output signal changes). The
output signal change takes the form of a long periodic interrupt, i.e. It
turns in andof at two second intervals.
-CONNECTION LEADS
The oscillaor comes complete with a set of connection leads and clips.
Alternatively, Cords Test 1/500A and Clips Test 38A may be used.
-IMPORTANT SAFETY NOTICE:
The moniter (headphone) output is only suitable for use with Recievers
Headgear 18A or 18A and Headsets 7A or 8A. Use of other headphones
mayresult in the users audio exposure exeeding safe limits.
2.2 AMPLIFIER 109H
-GENERAL
The amplifier has an integral probe and a loudspeaker output. Asthe
amplifier probe tip approaches the cable pair which the oscillaor signal is
connected, the clicks generated by the speaker become more frequent. This
enablesthe pair to be located even when high background noise levels exist.
A rotary sensitivity (gain) control is provided so that the Amplifier maybe
adjusted to suit the signal levels being detected.
-BATTERY STATE INDICATION
When the Amplifier is swiched on or off, the red indicator lightwill flash
once. This indicates that the battery voltage is adequate.
If the voltage falls below an acceptable level, the light will be on
continuosly. The battery must then be changed.
-HEADPHONE SOCKET
The output socket at the rear of tthe Amplifier allows the connectionof a
headphone (receiver Headgear 17A or equivalent).
Only the received 1kHz signal is provided to the headphone output. Theclick
rate signal and the loudspeaker output are disabled when the headphoneis
plugged in.
The headphone output system should be used when working in quiet areason
customers premisies, or where interfering signals from other sources are
present on the pair being traced.
-IMPORTANT SAFETY NOTICE
The headset is only suitable for use with Recievers Headgear 17Aor 18A and
headsets 7A or 8A. Use of other headphones may result in the users audio
exposure exceeding safe limits.
2.3 RECIEVER HEADGEAR 17A
This the `standard' headphone for use with the Amplifier or Oscillator.
2.4 RECIEVER HEADGEAR 18A
This headphone is designed for use with Helmets Safetly ....
2.5 ADAPTER TEST 49A
The adapter plugs into the customers' line jack unit to enable test access
to all six connections. The adapter is numbered to corrospond with
thenumbers rear wire connections of the line jack unit.
2.6 CORD CONNECTING 2/26A
The cord is provided for connecting between either the Amplifier of
Oscillator and a Telephone 286. This enables the telephone headset to be
used for communcation and tone tracing.
3. PRINCIPLE OF OPERATION
-GENERAL
The Oscillator provides a 1kHz signal which is connected to the pairof
wires to be traced or identified. The signal power is limited to 20mW. To
minimise interference to adjacent lines a sinusoidal waveform is used.
The signal sets up electromagnetic and electrostatic fields in the vicinity
of, and along the length of, the pair. These fields can be detected bymeans
of either an electromagnetic or electrostatic probe. The signal for these
probes is then amplified and presented to the user through either a loud
speaker or a headphone (reciever Headgear 17A or equivalent).
Induction of the 1kHz signal into ajacent pairs balances itself out giving
negligble crosstalk (interference) to working circuits.
-ELECTROMAGNETIC DETECTION
Where a magnetic detection system is required. (usually only
necessarywhere idenfication of a cable is requiresd) the Tester 453A is
used. This isused in conjunction with the Oscillator 87, provided as part
of the Tester 132C. Principles of magnetic detection and the use of the
Tester 453A are detaield in the suers handbook with the tester 453A.
-ELECTROSTATIC DETECTION
The Tester 132C provides the 1kHz Oscillaotr and an electrostaticdetection
system.
The electrostatic method is employed for the location and identificationof
individual cable pairs. For electrostatic detection the oscillator signalis
connected directly across the cable pair to be identified or located. If
possible, the pair should be open circuit to ensure the highest
signalvoltage at the detection point.
The amplifier 109H detects the electric field resulting from the voltage
across the pair. For maximan flexibility, two output systems have been
incorporated in the amplifier.
The loudspeaker control is the `normally' used system. This is built inthe
Amplifier. The level of the signal detected by the probe is represented by
a varible click rate (pitch) output from the loudspeaker. The closerthe
probe is to the desired pair, the higher will the click rate of the output
from the loudspeaker.
The alternative to this system is the headphone output. This enables
theuser to listen to the signal being radiated by the pair being traced.
The closer the Amplifier is held to the pair, the louder will be the sound
outputfrom the sound outout from the headphone.
4. USING THE OSCILLATOR 87G
The oscillator is connected to the pair to be traced at a convientent
point- typically at a flexablilty point such as an exchange frame or a
street cabinet.
To prevent interference to customer service, care must be taken to avoid
connecting the oscillator to working circuits.
Plug the connecting leads supplied into the output sockets of the
oscillator. Switch the Oscillator on and connect the leads to A and B wires
of thecable pair to be traced using the appropiate test clips or adaptors.
(As the connection is made the `SHORT' indicator on the top of the
Oscillator may illuminate briefly).
If a headphone is connected, satisfactory connection to line is indicated
by a low level tone (the tone may be at the higher `short' indication level
for a brief period after inital connection)
Adjust the Oscillator output to give an interuppted or continuous toneas
required.
Always replace the headphone socket sealing plug when the headphone isnot
connected.
The Oscillator must not be connected between earth and the wires as this
will increase the level of tone induced into other pairs. This will
alsomake positive tracing and identification of the pair difficult and
could result with interference with communications traffic on the cable.
The Adaptor Test 49A supplied with the Tester 132C ensures the Oscillatorto
be connected to a Line Jack Unit. Other adaptors are often providied with
frame and cabinet block systems for test access purpose. These should
beused, where available, to ensure a reliable connection to the pair to be
traced.
Connection to a `live' exchange line will reduce the signal available onthe
line and may make the tracing operation more diffilcult. If practicle,where
the Oscillator is connected at an exchange frame, the exchange connection
should be removed by the approved method for the type of block being used,
i.e insertion of the appropiate wedge or removal of the line fuses.
5. USING THE AMPLIFIER 109H
5.1 LOCATION OF A PAIR AT A CABINET (OR PILLAR)
One press of the `ON' switch turns the Amplifier on. The loudspeaker output
will emit two short `clicks' every second, evan when no signal is being
recieved by the probe.
A further press of the switch turns the amplifier off.
Initially, set the sensitivity control to it's mid point. Move the
amplifier over the terminal strips where the wanted pair is expected to be.
If the click rate of the amplifier does not change, turn the sensitivity
control toward its `FAR' setting and repeat the search.
If the click rate does not increase at any point, then the rest of the
cabinet should be searched with the Amplifier until the approximate
location of the pair is found.
The sensitivity control is then turned towards it's `NEAR' setting until
sufficient discrimination is available to enable accurate location of the
pair.
If the identification is in doubt, this may be confirmed by shorting the
wires if the identified pair together - when this is done the click rateof
the Amplifier will drop significantly if the pair is the correct one.
Where applicable, metallic contact must be made by use of the
appropiatetest clips or adaptors. The exact method employed will depend on
the type ofcross connection system fitted in the cabinet. On no account is
contact to, or shorting out of, the pair to be achieved by cutting into
cable insulation with knives or other insulation piercing devices.
It should be noted that the Amplifier discrimination will always be better
between pair if the sensitivity setting is kept as low as possible,
i.eclose to the `NEAR' setting.
5.2 LOCATION OF A PAIR AT A DISTRIBUTION POINT (DP)
For pair location at a DP the Amplifier sensitivity control will
normallyneed to be set close to the `NEAR' stting. Location is usually so
positive that shoring out the pair is unnecessary.
5.3 LOCATION OF A PAIR IN A CABLE JOINT
To find a pair within a joint the Amplifier sensitivity should be adjusted
such that an increase in click rate is achieved when the amplifier probe is
close to the joint. Search of the units of the joint to identify the unit
containing the wanted pair. When this has been located, the sensitivityis
further reduced (turn the control towards the `NEAR' setting) to allowthe
individual pair to be found.
Maximum clikc rate will be achieved when the probe is adjacent to the `A'or
`B' wire with a drop in click rate noted when the probe is placed between
the two wires.
If more posotive indentification is needed, the located pair can be shorted
out to confirm the identification. Ensure that the pair is correctly
reinstated using approved practice.
5.4 CABLE CHANGEOVER OPERATIONS
The use of the Amplifier is as described for the location of pairs in a
joint.
When the Amplifier operator shorts to verify the location, the operatorat
the Oscillator end will recieve an indication of this (see section 2.1-
DETECTION OF LINE STATUS). This will indicate correct location of the
pairto both users.
The Oscillator moniter output and/or the Amplifer headphone output maybe
fed into the `AUX' input of the Telephones 286 being used to communicate
between the two operators. The Cord Connecting 2/26A is used to make the
connection.
This facility connects the Oscillator monitor output or the Amplifier
headphone output to the reciever of the Telephone. This enables the
telephone headset to be used for communication and tone tracing.
6. CARE AND MAINTENANCE OF THE TESTER
The tester 132C and it's component parts are designed for use in an
external engineering enviorment. When the Tester is not in use, additonal
protection is providied by the storage pouches and carrying satchel.
The headphone socket sealing plug forms an important seal against the
ingress of moisture. Always replace the headphone socket sealing plug when
the headphone is not connected.
The only routine maintenance required is to keep items forming the Testeras
clean and dry as is practicle. If the cleaning is necessary, a cloth
moistened with a warm, mild detergent solution should ne used.
It is particulary important that spent batteries are removed from the
Amplifier and Oscillator. Only maganese alkaline batteries are to be usedin
this items, i.e LR6 for the Oscillator 87G, 6LR61 (6LF22) for the amplifier
109H.
[oFFICIAL eND oF dOCUMENT]
Right, in addition to all this, it is possible to trace a cable pair
without the use of an Oscillator.. the test service 176 can be used for a
localnumber and will apply a trace tone to the number you enter after 176
(full national code must be used). To check for correct line, then apply a
ground of 2kms thro the cable pair, if the correct line has been identified
then the user dialling 176 will recieve the NU tone (continuous tone).
Whilst this service is in use, noone may dial the subscribers line as it
would be busied out.
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