Newly installed FTCC phone no longer rings

[#1]

Bizare problem I have here.
1. BT Openreach turn up Monday install the filter and modem.
2. New service works well.
3. The extention phones no longer rings.
If I plug the phone in the master socket it rings OK. I have re-wired used test meter to check cables removed all filters isolated the 2 extention circuits from the master socket at no point can I get my phone to ring on either extention. The phone displays the caller ID and if I pick it up can conduct a call, and I can make calls from the phone. The other extention has a DECT phone and if I swap the DECT phone for the standard phone the DECT phone rings OK I suspect it is because it has a power brick and batteries in the handset.
It is like the line power has dropped at the extention and there is not quite enought oomph to get a phone to ring on an extention, but can at the socket.
In the master socket I have just 2 wires connected teminal 2 and 5 and this is how I have always installed extentions. I know the terminal 3 (I think) is used to stop extention phones tinkling called the bell wire, but I don't need that as the standard phones are push button DTMF phones and not the really old rotary dial type.
I am at a loss as to know what to do next as BT want to come out test the master socket and say all is OK here then charge me £130.
Any suggestions would be most welcome (apart from buying another DECT phone)

[#2]

I am no expert, but did you try plugging in a micro filter at the extension socket?
From what I know they generate the ring signal that the bell wire normally carried.
Maybe your phone can't generate it's own?
If there is enough power to make a call, then it should be enough to get the phone to ring.

[#3]

TBSteve thanks for your suggestion.
As I understand the FTTC trial requires the fliters to be removed (The BT Engineer also advised me to remove them) as they can attenuate the signal.
I'll give it a try .......
..... Tried it it works I really don't understand why goes against what was recommend by BT etc.
Do you think if I connected all 4 wires from the BT master socket to the extentions it would work?

[#4]

I'd say you only need to reconnect Terminal 3 (the bell wire) and then you should be OK.
Or you could simply leave the filter connected to that phone.

[#5]

yeah, i think vip3rs right, sounds like your phone needs the bell signal from the master/filter to work.

[#6]

Yes indeed - the modern way to wire things is to leave the bell wire (the #3 wire) disconnected. This is to stop it from acting as an aerial and adding interference to the ADSL signal.
In older setups, the master would split the ringing signal off the 2 incoming lines using a big capacitor, and put that on wire #3 to the internal secondary sockets. An old phone expected this to have happened in the socket, which is why one phone doesn't ring. New phones don't need a signal on the #3 wire - they detect the ring on the main pair instead. This is why the DECT phone can ring, even when the other phone can't.
Filters have circuitry that re-introduces the ring signal on the #3 wire, which is why the old phone then works again.
If I had to choose between re-introducing the #3 ring wire in the internal wiring, or just use a filter for that phone, I'd probably choose to do the latter.