My 79 year old mum's landline phone isn't ringing properly. It just gives one long ring then stops. Calling out is fine. I've been trying to track down the problem for her. She has a fairly complex set-up with extensions, broadband, an automatic panic alarm box etc. I've gone through every socket and checked ADSL filters etc etc, I've tried replacing the phone, but still the problem persists. BT can't find a fault with their line checker. BT of course are happy to send an engineer out, but will charge a fortune if the fault is beyond their master socket. My mum can't afford the cost. How can I determine whether the fault is a BT one? Are their freelance engineers out there that could check everything out for less than £200?

Disconnect everything until you are left with just the master socket. Now plug in an ADSL filter the the test socket (remove the lower half of the BT faceplate to access this.)
You are now right on the edge of BT's network. Plug a telephone into the filter as you normally would. Phone it. What happens? If the fault has gone, then the problem lies within the house. If the fault is still there, call BT.

Actually dispense with the filter.

Plug the phone and only the phone into the test socket. Try more than one phone just to be sure. If you get constant ringing then the fault is with the BT line.

If not try with an ADSL filter. If you now get constant ringing the filter may be faulty so try another one. Basically work through them all to check they all work properly

Next double check all your extension wiring. I have known odd things happen occasionally if you get the line pair reversed, ie terminal 2 on the master socket wired to 5 on the extension and master terminal 5 to extension terminal 2.

Also remove any wiring to terminals 3 and 4 if there is any. Terminal 3 is the bell wire which is only needed if you have secondary extension sockets without their own ring capacitors. But as you have ADSL the filters you have to use on all extensions have ring capacitors anyway so the bell wire is redundant. But it has been known to cause problems with ADSL so might be worth removing.

Terminal 4 is an earth connection. not really used on domestic installations. Mainly used if you have your own switchboard for services like call divert.

If you don't use a filter then the high frequency ADSL signal will be present at the phone - probably not a problem but i would have thought that keeping the set-up the same as in normal operation would be better.
There is no "ringing" capacitor in a micro-filter, just some induction coils in series with each other (which offer a high resistance to high frequency AC signals) in both legs with a balancing capacitor across them, and a low value resistor, (about 20 ohm) in series with each leg

The ADSL signal is always present at the phone, it is the phone that is filtered not the ADSL signal, to stop interference with the ADSL.

The balance capacitor acts as a ringing capacitor that is one reason why you can disconnect the ring wire and phones will still ring, though most modern phones do not need a ringing capacitor anyway.

The ADSL signal should not affect ringing.

Most, if not all, of the filters i've taken apart have a capacitor connected to pin 3. Though more and more phones these days don't need anything on pin 3 to make them ring.

The whole point about not using a filter is it is one less thing to affect the test. By pluging just a phone into the test socket you only have two options if it doesn't work, the line or the phone. If you have a filter in circuit then that is another point of failure to eliminate.

Just that in many years fault finding i always reduce everything to it's most basic working state to begin with and test that. Then start to make it more complex untill you find the bit that is screwing it all up.

I've seen this happen before, it's usually a fault at the exchange, but excellent advice above, very well put. Eliminate everything in your house by using the test socket inside the master socket.

Wow! Thanks for all the responses.

My mum doesn't have a modern master socket. The 'master socket' is one of the old BT ones, about 2" square with the 'T' logo (pre prancing man). This is extended to 3 other sockets.

Where the main line enters the house, the ancient wires are connected to an old oval box that's not screwed to the wall, and has no top. There is green copper corrosion on the terminals.

It's a mess of a system that's been mucked about with and extended several times over the last 40 years.

If she had the later NTE5 master BT would charge for any internal faults after the master

As it is the older hard wired master all the internal wiring is BT's responsibility and there should not be any charges for fixing any problems.

It's the other way around - the phone signal is present everywhere, not the ADSL.
Here's a diagram which kind of shows what i said in an earlier posting, so maybe i should have linked it to here earlier.
Here it is anyway >>>>> http://www.accesscomms.com.au/images...ilter-do-2.gif

I think the rule used to be that you could do extensions yourself but BT had to make the connection to the master unit, so be careful as they will probably still say that the extensions belong to you.
Then when the new style lineboxes came along you were allowed to make the connection to the faceplate yourself as you could effectively isolate your own work from the BT network if need be (for fault finding purposes)

Just like to thank everyone for the help they gave with this issue. I discovered that where the main wiring came into my mum's house, the junction box had corroded terminals. I cleaned it all up, stripped the wires and rewired it, and bingo, everything works perfectly! Cost - nil! (well apart from the cost to my sanity)

we would have repaired that for free, and changed it out from a screw type to IDC(crimp) type. but oh well, saves a job for us.

The OP couldn't have known that though? Either that or he wasn't prepared to take the risk!

thats true, however by doing what they did they actually breach their contract with their CP as they meddled in our wiring.
there is an agreement between us and the CP's that we will visit and change out the LJU to a NTE5, for free on a fault providing that work beyond the nte5 hasn't been authorised by the CP. so if we had gone and the fault was beyond the LJU, we would have fitted the NTE5 and disconnected the faulty ext'n. etc. and the EU would not have been charged. we would have then standardised the wiring coming into the house by upgrading the junction box or if the cable feeding the property was of an obsolete type change that out aswell.

But had he tested as recommended (unplug everything after the first socket, even if it's hard wired, remove it), the fault would have still been there, so BT could have been called.

Well, would it be apparent to any subsequent BT engineer that work had been done here? And would they then get snotty about it, if they can see a tidy job had still been done?

I did exactly that and then phoned the BT faults number when we had severe noise on our line. I explained to the lady that the fault was intermittent, she clearly heard the noise and acknowledged its presence. The engineer came out, couldn't find any fault so sent me down the road with a pole, had me shake the wires in order to try & recreate the fault. He left having done nothing and charged me £100 for the privilege. BT are totally disgusting.
Similarly with mother-in- law who was quite ill, she had an alarm system installed& was obviously dependant on a good phone line. I had dire warnings about being charged £100 if they found nothing wrong. The engineer came out found nothing, then said that he would make up a suitable story to avoid mother -in-law paying £100 from her pension. I had to find the fault myself, it was a very obvious worn connection, before he came out again and fixed it.
The phrase lower than a snakes belly comes to mind.

That's a laugh !