British Telecom Testing Equiptment 

Typed by Dosile & Psyclone e | 
P D D P 
+ --------------------------------- 132 C ----------------------------------- + 

 > 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 be more 

The equiptment must only be used in the manner and purpose specified in this 
handbook or approved documation. 

No unapproved modifications are to be made to this equiptment. 

2. Description of the Equiptment Items 



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 may be 
continuous, or interrupted at between 2 and 10 pulses. The ootput is set by 
a single rotary control. 

If desired, the output signal can be monitiered whilst the rate is being set. 
This is achieved by listening to a headphone connected to the monitor 
socket and with the output sockets shortened (loopened) together. 


 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 will be 
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. 


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 conditions will 
not operate reliably. 


A battery state indicator lamp (`BATTERY') is provided on the Oscillator. 
When the Oscillator is on, this indicator will flash for approximately flash 
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 and of 
at two second intervals. 


 The oscillaor comes complete with a set of connection leads and clips. 
Alternatively, Cords Test 1/500A and Clips Test 38A may be used. 


The moniter (headphone) output is only suitable for use with Recievers 
Headgear 18A or 18A and Headsets 7A or 8A. Use of other headphones may result 
in the users audio exposure exeeding safe limits. 



 The amplifier has an integral probe and a loudspeaker output. As the amplifier 
probe tip approaches the cable pair which the oscillaor signal is connected, 
the clicks generated by the speaker become more frequent. This enables the pair 
to be located even when high background noise levels exist. 

A rotary sensitivity (gain) control is provided so that the Amplifier may be 
adjusted to suit the signal levels being detected. 


 When the Amplifier is swiched on or off, the red indicator light will 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. 


 The output socket at the rear of tthe Amplifier allows the connection of a 
headphone (receiver Headgear 17A or equivalent). 

Only the received 1kHz signal is provided to the headphone output. The click 
rate signal and the loudspeaker output are disabled when the headphone is 
plugged in. 

The headphone output system should be used when working in quiet areas on 
customers premisies, or where interfering signals from other sources are 
present on the pair being traced. 


 The headset is only suitable for use with Recievers Headgear 17A or 18A and 
headsets 7A or 8A. Use of other headphones may result in the users audio 
exposure exceeding safe limits. 


This the `standard' headphone for use with the Amplifier or Oscillator. 


This headphone is designed for use with Helmets Safetly .... 


The adapter plugs into the customers' line jack unit to enable test access 
to all six connections. The adapter is numbered to corrospond with the numbers 
rear wire connections of the line jack unit. 


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. 



 The Oscillator provides a 1kHz signal which is connected to the pair of 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 by means 
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. 


 Where a magnetic detection system is required. (usually only necessary where 
idenfication of a cable is requiresd) the Tester 453A is used. This is used 
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. 


 The Tester 132C provides the 1kHz Oscillaotr and an electrostatic detection 

The electrostatic method is employed for the location and identification of 
individual cable pairs. For electrostatic detection the oscillator signal is 
connected directly across the cable pair to be identified or located. If 
possible, the pair should be open circuit to ensure the highest signal voltage 
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 in the 
Amplifier. The level of the signal detected by the probe is represented 
by a varible click rate (pitch) output from the loudspeaker. The closer the 
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 the user 
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 output from 
the sound outout from the headphone. 


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 

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 the cable 
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 tone as 

Always replace the headphone socket sealing plug when the headphone is not 

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 also make 
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 Oscillator to 
be connected to a Line Jack Unit. Other adaptors are often providied with 
frame and cabinet block systems for test access purpose. These should be used, 
where available, to ensure a reliable connection to the pair to be traced. 

Connection to a `live' exchange line will reduce the signal available on the 
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. 



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 

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 rate of 
the Amplifier will drop significantly if the pair is the correct one. 

Where applicable, metallic contact must be made by use of the appropiate test 
clips or adaptors. The exact method employed will depend on the type of cross 
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.e close 
to the `NEAR' setting. 


For pair location at a DP the Amplifier sensitivity control will normally need 
to be set close to the `NEAR' stting. Location is usually so positive that 
shoring out the pair is unnecessary. 


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 sensitivity is 
further reduced (turn the control towards the `NEAR' setting) to allow the 
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. 


The use of the Amplifier is as described for the location of pairs in a 

When the Amplifier operator shorts to verify the location, the operator at 
the Oscillator end will recieve an indication of this (see section 2.1 - 
DETECTION OF LINE STATUS). This will indicate correct location of the pair to 
both users. 

The Oscillator moniter output and/or the Amplifer headphone output may be 
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 

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. 


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 Tester as 
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 used in 
this items, i.e LR6 for the Oscillator 87G, 6LR61 (6LF22) for the amplifier 


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 local number 
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. 

Back to document index 

6Mb free web space. Click here. 6Mb free web space. Click here.