GPO 746 bell tinkle problem

[poplar1]

And just to clarify things a bit with terminology, here in the UK, it's not called "P&S", its PSTN, Plug and Socket Telephone Networking...

I thought PSTN = Public Switched Telephone Network, the pre-VOIP global method of interconnecting calls.

[Jack Ryan]

I thought PSTN = Public Switched Telephone Network, the pre-VOIP global method of interconnecting calls.

That's right.

The system of master and extension sockets that uses a common capacitor is called "New Plan" or more generally, "Plug and Socket". I'm afraid I get lazy and call it P&S, usually after defining it. I forgot this time.

Jack

[andy1702]

Hi Barry,

I'm also in the UK and started with a very similar situation to what you have, master socket miles away from my router and a couple of extensions. I too had broadband issues, so went into every socket and disconnected the bell wire. The phones still ring because, as you correctly worked out, all the ADSL filters have a capacitor built in and you should have a filter at every socket. So then I effectively had a two wire system (using 1 pair) throughout the house. All the phones (a mix of old and new) are converted to plug and socket where necessary and there is never any bell tinkle on any of them.

What I think you need to do is make sure the bell wire is disconnected at every socket. Then make sure every socket has a working ADSL filter fitted. be warned though, these filters can (and do) fail occasionally and they should be the first suspect if you experience any problems in the future. Next you should make sure every old phone connected is correctly converted. That image of the wiring diagram you posted is exactly the same one that I use and it's spot on.

What actually happens when you convert, say, a GPO 706 to plug and socket wiring is you over ride the capacitor (or condenser) in the phoneand alter the wiring so it uses the one in the master socket to generate the ring. As you've removed the ring wire connected to the master socket that's why your phones didn't ring until you fitted the ADSL filter which also has a capacitor built in.

Pre-plug and socket wiring (like the 706 originally was) relies on the capacitor in the phone to generate the ring.

So to recap... You've done the right thing removing the ring wire (often called the anti-tinkle wire) from the sockets. Just make sure it's disconnected everywhere. You've also done the right thing having your phones converted to the modern plug and socket system. It means they have more value if you come to sell them and you can also take them places and just plug them in. The final point is to make sure anything plugged into any socket is going through an ADSL filter.

Now, regarding a splitter faceplate, I never used one. In my case the two wire drop cable comes into the master socket in the front room, where there is also a telephone. The router is in an extension right out the back of the house where there is another phone. All this is joined up with 4 pair cable. What I did was to use one pair of my domestic cable to carry the combined signal from BT's incoming cable in the back of the master socket right round the outside wall of the house to the back extension where it comes inside. Here there's a standard extension socket (with just the single pair connected) with an ADSL filter to take the broadband to my router. The filtered phone signal from the filter then goes into an old BT Revelation PABX as an incoming line. One of the Revelation extensions then goes back down the same cable round the outside of the house using one of the spare pairs, back to the front room where I installed a second socket to plug a phone into. Because this signal is already filtered and I need to generate a ring, this second socket is actually anotehr master socket because I need the capacitor in it to do the ringing. The original BT master has nothing plugged into it's face as all the connections were made on the back.

There are also various other extensions from the Revelation that go off all over the house, each one terminating in a master socket to generate the ringing.

Now, just to make things interesting there is also a VOIP C*Net line coming from an ATA which also goes into the Revelation as a second incoming line.

There are various benefits to this system.
1. There is absolutely no bell tinkle.
2. The Revelation does very relaible pulse to tone conversion, so I can use absolutely any phone for either normal phone line calls or VOIP without needing an ATA that accepts pulse dialling.
3. I can make internal calls from one phone to another.
4. Someone can be on the phone on line 1 while I'm talking from another extension to someone on C*Net using line two (VOIP).
5. The Revelation can be set to ring groups of phones, single phones or all phones. Handy if you don't want every phone in the house to ring in the middle of the night!

Best of all... The cost of this whole system was less than buying a singe Rotatone or Dial Gizmo. I think the ATA was about £12, the Revelation was picked up for £10 and the master sockets were about £1.50 each, all from E-Bay!

Andy.

[Jack Ryan]

The UK Plug & Socket wiring system is not always easy to comprehend.

Originally phones were self-contained; the bell capacitor (actually a dual purpose capacitor) was in the telephone and all was well.

Eventually subscribers started installing additional telephones and this caused problems with loading, false ring trip and bell tinkle. The Plug and Socket system was meant to address this by fitting a single capacitor in a master socket and feeding the bell and receiver circuits of the telephones from that via the "bell wire". Bell tinkle was suppressed because when one handset was lifted, the (low impedance) audio circuit bridged the line and effectively short circuited all the other bells via the "bell wire".

When ADSL was introduced, it was found that the Plug and Socket wiring unbalanced the line and adversely affected broadband operation. The solution seems to be to disconnect the bell wire and add an ADSL filter containing a capacitor for each telephone. This appears to mean that each telephone now has its own capacitor so the wiring has reverted to pre Plug and Socket.

If that is the case, I would reinstate the original telephone capacitor, use a central splitter and remove the individual filters.

Jack

[Owain]

Before parallel (New Plan) wiring, the 2x500 ohm bells in all phones were connected in series and the capacitor in the *first* phone was used as the ringing capacitor. Thus phones were strapped differently for first, intermediate and last in the chain.

On plug in systems pre-New Plan there was always a fixed phone or bellset to provide the ringing capacitor. The phones were strapped differently depending on whether there was one or more than one pluggable instrument supplied. The GPO considered it unacceptable to have a line without a ringing indication.

Using separate filters for each phone does not prevent tinkle because there is no anti-tinkle bell wire between all phones.

The best way, for both phones and broadband, is one latest spec Mark 4 master socket and filter.
https://www.run-it-direct.co.uk/mk4btopenreachvdslsocket.html

[Jack Ryan]

Before parallel (New Plan) wiring, the 2x500 ohm bells in all phones were connected in series and the capacitor in the *first* phone was used as the ringing capacitor. Thus phones were strapped differently for first, intermediate and last in the chain.

On plug in systems pre-New Plan there was always a fixed phone or bellset to provide the ringing capacitor. The phones were strapped differently depending on whether there was one or more than one pluggable instrument supplied. The GPO considered it unacceptable to have a line without a ringing indication.

The bells were officially connected is series here as well but I only saw parallel connections. In the USA (Bell System) phones were connected in series and parallel so that the impedance remained approximately that of a single phone.

Our portable telephones also used wiring that included a fixed bellset (just a bell).

Nevertheless, the current wiring with ADSL filter circumvents the bell wire and common capacitor and the phone circuit reverts to pre Plug and Socket.

Using separate filters for each phone does not prevent tinkle because there is no anti-tinkle bell wire between all phones.

No, that's right but if a 3k3 or 4k7 ohm resistor is fitted in series with the bells there may well be enough damping to suppress bell tinkle - it does here.

The best way, for both phones and broadband, is one latest spec Mark 4 master socket and filter.
https://www.run-it-direct.co.uk/mk4btopenreachvdslsocket.html

If that is a central splitter, that is what I was suggesting. The link is "forbidden".

Regards
Jack

[Owain]

If that is a central splitter, that is what I was suggesting. The link is "forbidden"

Sorry, I don't know why. It works here.

Same item, from Amazon
https://www.amazon.co.uk/dp/B01LHBF4GA/

[twocvbloke]

Them Mk.4 faceplates look pretty weird, especially coupled to that modernised NTE5... 

[Jack Ryan]

Sorry, I don't know why. It works here.

Same item, from Amazon
https://www.amazon.co.uk/dp/B01LHBF4GA/

Probably geographical filtering. The Amazon link works - thanks.

Is there a circuit diagram or block diagram? The Amazon page has "Bellwire filter provided" which could mean anything.

Regards
Jack

[twocvbloke]

The "Bellwire filter" basically means that the master socket hasn't got the ring capacitor connected anymore (heck, I don't think they even have capacitors in them now, just an out-of-service resistor!), and the faceplate has the xDSL filter built in plus a ring capacitor circuit for older BT-wired phones, as even relatively modern BT phones have still continued to be 3-wire, despite everyone else going to two-wire (because that's all that's needed)...

There's some pictures of the NTE5s and the xDSL faceplates here:

http://telephonesuk.co.uk/line_jacks.htm

No diagrams unfortunately...

[Jack Ryan]

The "Bellwire filter" basically means that the master socket hasn't got the ring capacitor connected anymore

English is a strange language.

Jack

[twocvbloke]

English is a strange language.

Jack

Nah, it's just technobabble speak to make the BT-Openreach guys seem like they know something that we don't...

[andy1702]

There's nothing to stop you using a two wire system. That's what I use. You just need to remember that if your telephone is wired for plug & socket then you need an external capacitor (either in the socket it's plugged into or in an ADSL filter) to make it ring. If you have something like a tele 706 or 746 that hasn't been converted, then it will use the onboard capacitor so you don't need an external one somewhere.

Personally I convert all my phones to plug & socket in case I ever want to sell them  or use them elsewhere in the UK.

Andy.

[royalbox]

Thanks for all the information, very interesting but it can get complex.

I have 4 746 phones at the moment and have been playing around with them  using the best parts to make up 2 good ones to keep. I have one with a single coil 500 ohm bell ringer. I notice when I use that (with a 3.3K resistor in series of course) I don't get the bell tinkle when I dial the other phone. The only one that tinkles is one that has 2, 2000 ohm coils (so no resistor). I've adjusted the bells about the same on all the phones so that the clapper just touches each bell when moved to either side.

I've decided to keep the one with the single coil because it also has a kind of volume adjustment lever that prevents the clapper hitting the bells so much.

I probably will redo the wiring with a new faceplate as mentioned though in the new year, and run the ADSL on a separate pair of wires (within the same cable). Just need to replace a short stretch of wire between the master and first extension because it is only 2 pair. The rest of the cabling round the house is 3 pair so won't need to redo that thankfully.

Thanks again,
Barry.

[Jack Ryan]

I notice when I use that (with a 3.3K resistor in series of course) I don't get the bell tinkle when I dial the other phone. The only one that tinkles is one that has 2, 2000 ohm coils (so no resistor).

I think I mentioned that earlier. The addition of a 3k3 or 4k7 Ohm resistor damps (filters) the bell circuit so it is much less likely to tinkle.

I've adjusted the bells about the same on all the phones so that the clapper just touches each bell when moved to either side.

It might be better if they just *didn't* touch.

Jack