Phone Line Faults

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Here is a brief guide to the most commons problems you will encounter with your home or business phone line. They are listed in order of the most common. But first, here's a basic explanation of how a phone line works.

Your phone line consists of 2 wires. Usually the wires are copper, sometimes aluminium. The one wire is the power (50v approx), the other wire is the earth. They leave the telephone exchange in big cables up to 2000 lines, then via a series of junctions and joints, they arrive at your house in a single cable.

I've used the BT technical term for each fault, plus given an explanation of what they mean.

  • Your phone line is completely dead. No dial tone. Probable causes are:

The line is DIS. This simply means the line test is not picking up the capacitance reading of your master socket. Basically, the line is broken through somewhere, so cannot complete the cicuit to give you dial tone.

The line is LOOP. Or in other words, the line has a short cicuit on it. The 2 wires are touching somewhere, so again cannot complete the cicuit.

  • Your line is very noisy. May have dial tone, may cut off while using the phone.

Noise faults usually fall into one or more of the 4 categories below:

Battery Contact. This means your line is in contact with another line. Usually caused by water in the system causing the insulation on the wire to break down. Unless you have more than one line, it will always be a network fault. You may or may not have dial tone, dependent on how much it is in contact with the other line.

Earth Contact. Your line is going to earth somewhere on it's route to you. Maybe a tree has rubbed it through. A local farmer has hit it with his plough or hedgecutter. Could be anywhere in the system.

HR Dis...or high resistance dis. When one wire (sometimes both wires) of your line is struggling to make contact. Again, possibly caused by a tree rubbing on your line, or maybe in a joint in the network which has not been touched for years. You will usually have dial tone ok, but will be very noisy.

Rectified Loop. This is a one way loop usually caused by damp in the circuit. Mostly this is an internal fault in your house, but not always. You will recognise the symptoms as when someone rings your number, your phone will only ring once then cut off.

There are several other reasons why a phone line will not work, but the above ones are the most common by far.

If you do get any sort of fault on your line, it always pays to locate your master socket...usually downstairs in the hallway or lounge. It is quite large, about the size of a mains socket. On the master socket you will see 2 small screws. Unscrew these and carefully pull off the lower plate. This plate should have all your extensions around the house connected to it, so go careful not to dislodge any wires. You'll then see you can plug a phone into the body of the socket (the lower plate covers this, so cannot be seen until you take the lower plate off). Test your line here. If it is still faulty, call your service provider.

If your line is testing loop or rectified loop, try unplugging all phones, sky tv, fax machine...everything. This is especially important after lighning has been in your area, as lightning close by can knock out sky boxes, fax machines and dial up modems.

The BT national line test number is 17070. It will only test BT lines. BUT, since I wrote this guide, the line tester will now only function for BT authorised engineers. No members of the public can use it.

If you found this very brief guide useful, please say so.

Must go now. More phone lines to repair.


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