Digital Voice over FTTC with extensions

[wkirkman]

Hi there. First off, establishing a few things:

- I have been informed that BT are going to change me over to Digital Voice (VoIP) within the next couple of months.

- I have been preparing for this even before them telling me, assuming it would happen at some point soon.

- I have FTTC not FTTP and so still use the copper phone line for the VDSL2 connection.

- I have telephone extensions running to an Annex building at the back of the main house, which needs to remain working and as with the following scenario, have no need for the adaptors they offer.

So, in preparation, I have made up a cable with a single BT Plug on the end. When the switchover happens, I was going to unclip the extensions from front of the NTE5c plate, and jelly crimp wires 5, 3, 2 onto the counterparts of the made-up cable, and plug this into the back of the BT Smart Hub 2 telephone socket. Thereby, allowing the Smart Hub 2 to kick out the analogue phone signals directly onto the extension wiring, keeping the Annex phones alive.

I see no problem with doing this, and this is still my decided way forward at the moment.

HOWEVER… I have been giving it thought, and the below scenario 'could be' possible, and would be simpler:

Make up a cable with two BT ends, plug one end into the Smart Hub 2 and the other into the main Phone socket on the MK4 VDSL2 filter faceplate. The phone signal would then go into this socket and light-up the extensions at the same time. I don't use this socket for a phone, so it is free to use.

I am, however, unsure as to what would then happen further back. Because it is FTTC the A and B wires still need to be connected at the back of the NTE5c socket to provide the VDSL2 connection. The PTSN equipment at the exchange will no longer be active on the other end of those cables, but, being just copper cabling, the phone signalling, including any incoming ringtone 'will likely' go back up those two wires, back toward the exchange.

So, my question for those hopefully more in the know that I, is: If I did it this way, would or does it cause any issues with internet connectivity, or any other issues I have not foreseen here?

I personally don't think it will, as the telephone signalling is there on a normal PTSN/DSL mix anyway. It only normally becomes a problem when going to the receiving modem/router at Customer Premises if unfiltered as the modem/router will drop the connection.

However, if anyone could think of legitimate concerns as to why this would not work, please let me know here?

Obviously, if this was FTTP I wouldn't have the issue as there would be no copper in A/B anymore, but alas, I cannot get FTTP yet.

Any help with the logic of this scenario is appreciated. Many thanks.

William

[imjolly]

up to you if you want to try it but should you cause any damage to openreach line then you will be billed

much simpler would be just to use an extension socket next to master and connect your extension cable currently in master to 2&5  (3 no longer need) then connect cable from hub to extension socket making existing phone connections live

[licquorice]

First of all you only need to connect the wires from 2&5, 3 is not needed.

I'm not entirely sure of the arrangements at the DSLAM and whether it will change with digital voice. I suspect the telephony 50V and ringing supply are isolated from the broadband component at the DSLAM but obviously not at the CPE. However, if the DC and ringing component is fed back from the CPE  I'm not sure if the broadband component will still have any isolation at the DSLAM after changeover. It may also affect the ability of the HUB ringing current to actually ring the extension phones.

[wkirkman]

@imjolly Thanks for the reply. However, that is pretty much the same as my first solution, just with the extra step of connecting an extension socket to the wall (which will soon end up with more holes than bricks the way I drill 🙂 )

[wkirkman]

@licquorice That makes sense. So, my first solution is more elegant by not feeding back into A/B at all. Great, thanks.

[licquorice]

It's certainly the safest option.