16 March 2006





1                   Do not drop the transformer.

2                   Do not allow the crocodile clips to make contact with each other as this will, after several seconds, result in overheating and eventual burn out of the internal parts.


The enclosed pen-like device, an AC/DC Voltage Sensor, will buzz and light up if held close to a wire connected, for instance, to the mains.  You simply press the pen-clip to make it work.  Try it against the lead going to your electric kettle.  If the plug in the wall is switched on, you hear it buzz even if the kettle itself is turned off.   NOTE: no current has to flow for this Sensor to work.


WARNING: The sensor will 'chirp' if tapped against anything.  Do not confuse this intermittent chirp with the constant buzz that indicates voltage.


This then provides a quick way of finding a break in an Invisible Fence wire loop.  As mains electricity is DANGEROUS, we also enclose a 50 volt transformer to provide enough voltage to activate the sensor, but not enough to severely shock you.


Try plugging the transformer into a socket inside the house and laying both crocodile clips on the carpet. You can just feel a faint tingling if you hold both crocodile clips.  Try holding one clip in your hand and then bring the sensor close to the other crocodile clip lying on the carpet.  The sensor will buzz.  Bring the sensor next to the crocodile clip you are holding; you will get no buzz because you are “earthing” that clip.  Drop the clip you are holding and pick up the other clip; you will find the clip you leave lying on the carpet will now activate the sensor.


NOTE: This method is only suitable for finding breaks in wire above ground, where you can hold the sensor close to the wire.  If you find that you have a break in a buried length of wire, please contact us for further instructions.



889716 - or FAX us on (01305) 889718 - IF YOU HAVE


Invisible Fence (Wessex) LLP

 Westwood House Bradford Peverell DORCHESTER DT2 9SE




Plug the enclosed 50 volt transformer into a three pin outlet near your Invisible Fence transmitter.   DO NOT switch on the outlet yet.


Disconnect the transmitter from BOTH the loop wire ends.


Connect ONE of the loop wire ends to one of the wires fitted with crocodile clips coming from the bottom of the 50 volt transformer.  The other loop wire end is left dangling in the air unconnected.


Connect the other crocodile clip coming from the 50 volt transformer to an earth point, such as a wire connected to a metal rod hammered a foot or so into some damp soil.  A garden fork works quite well too.   (If you cannot reach the earth rod or garden fork with the short wire on the crocodile clip, use an extra bit of wire to connect the earth rod and the crocodile clip.)   YOU MUST MAKE THIS EARTH CONNECTION OR THIS METHOD WILL NOT WORK! Connecting this earth wire to the earth socket of a three pin plug can sometimes give spurious results and should be avoided. Now, switch on the electrical outlet.


Hold the voltage sensor near to the crocodile clip connected to the loop wire, which is now 'live', with 50 volts A.C. above earth.  It should buzz just as the kettle wire did before.


If you cannot get a buzz from the crocodile clip connected to the loop wire, check your earth connection on the other crocodile clip, and also make sure the crocodile clip making the connection to the loop wire is not resting against something that is earthing it.  If your earth contact is not good enough, you will find that the sensor buzzes when brought near the earth wire and stays silent when brought near the wire attached to the loop.  If you have this problem, try hammering the earth rod another foot deeper and watering the soil for six inches or so around it.  Also, the method fails in very dry soil conditions.  In that case, try at dusk as the dew falls or -- even better -- in the early morning before the dew lifts.


If you STILL cannot get the loop wire to buzz, the loop may be earthed at some point; the wire may or may not be broken as well.  This is often the case if the transmitter loop light is still on.   Cut the loop wire at the first wire join around the garden, suspend the cut end in the air above the ground, and see if you can get the sensor to buzz as far as the cut.  If you can, rejoin the loop and proceed around the loop cutting the wire every 100 metres or so.


Walk around the garden holding the sensor against the loop wire following the buzz until the buzzing stops.   When it stops you have found the break.   WARNING: Breaks are sometimes not visible if the outside insulation is undamaged or if a join has parted underneath a winding of black tape.


Repair the break by cutting out any damaged section of wire, and stripping some insulation from the wire ends.  If necessary, splice in a good piece of wire. Clean any black corrosion off the wire ends with sandpaper, and twist the bared wire ends together with plenty of wire overlap.  Wrap the join tightly with black insulating tape.


Continue around the loop, testing with the sensor just to make sure there are no other breaks.  Return to the transmitter again and check that with one end of the loop wire connected to the 50 volt transformer the other unconnected end of the loop wire activates the sensor, indicating the loop is complete.  IF THE ENTIRE PERIMETER WIRE BUZZES, BUT YOU CANNOT GET THE UNCONNECTED WIRE AT THE TRANMITTER TO BUZZ YOU MUST HAVE A BREAK SOMEWHERE ALONG THE TWISTED PAIR.


When you have got the buzz going right round the loop and right back to the unconnected end of the loop wire by the transmitter, this indicates the loop is complete.


Disconnect the 50 volt transformer wire from the loop, reconnect both loop wire ends to the transmitter, connect the transmitter to its 14 volt transformer and plug the 14 volt transformer into the mains socket once again.  The transmitter light should now indicate the loop is intact and the collars should buzz when brought near the Fence.  


If the transmitter still indicates the wire is broken phone us for further instructions.


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Please return the voltage sensor and 50 volt transformer to Invisible Fence (Wessex) as soon as you can.  OTHER CUSTOMERS MAY BE WAITING TO USE IT.