New wired 'phone not working after BT visit - Page 1
Forum section: electronics / projects

author: 741
author_rank: Frequent Contributor
timestamp: December 31, 2022, 04:38:00 pm
content: I've got a copper/wired broadband connection. Some months ago BT visited and bypased the downstairs master socket, keeping only the 'A' and 'B' wires. These were routed upstairs to a new 'Master Socket 5C', right near the router.The BT engineer mentioned the BT 'phone I was using seemed to be noisy. After the visit, I tried a much newer 'phone (from Aldi) - but the new phone failed to operate (no power, nothing). Maybe I should have simply gone through the process of booking another BT visit, but I assumed it was simply a couple of wires not connected.Now I look more in detail today, the problem seems not so easy to solve practically speaking - see picture. I do not know if there is any circuitry inside the new socket, but essentially I now have A & B to the two outer connectors (1,4) of the RJ11. The old BT phone works fine - although I am a bit confused by the fact it seems to implement 3 sprung contacts rather than two or four.The new phone uses the centre pins 2,3 wheras the BT phone uses 1,3,4. There is no way to change the Master Socket wiring to suit the new phone - it' seems 'set in stone'. What is the best solution I can install here - looks to me like I need to use a cable taking pins 1,4 from the master and routing to 2,3 to suit the newer phone?

author: wasedadoc
author_rank: Super Contributor
timestamp: December 31, 2022, 09:27:13 pm
content: Not clear what you are doing. The standard BT phone connector is not RJ11. The NTE box has two sockets. One is RJ11 for connecting the xDSL signal to your broadband modem. The other is a BT style phone socket. There is a low pass filter network between the incoming line and that socket which has the dual purpose of keeping the broadband signals from reaching the phone and stopping the phone adversely loading the line at the frequencies of the broadband signal.You new phone should have its cable terminated in a BT style phone plug or be supplied with an adapter to achieve the same functionality.If the new phone (or DECT base station) has a RJ11 socket on its body, ensure you are using the cable supplied with it. Other cables you already have may not be wired appropriately.

author: tooki
author_rank: Super Contributor
timestamp: December 31, 2022, 10:48:40 pm
content: Quote from: 741 on December 31, 2022, 04:38:00 pmFirst of all, just a quick, but important, correction: your pin numbering is wrong, in that it’s a 6-pin connector, not 4, so your numbering is off by 1. Standard pinout (like the Aldi phone) uses pins 3 and 4. And your old BT equipment is pins 2, 4, and 5.A bit of quick googling says that the phone end of a BT cord can use pins 3 and 4, or use 2 and 5.

author: wasedadoc
author_rank: Super Contributor
timestamp: December 31, 2022, 11:42:52 pm
content: A single line phone will use pins 2 and 5 of the BT style plug. (The type with the latch of the thin side.)

author: 741
author_rank: Frequent Contributor
timestamp: January 01, 2023, 06:48:32 pm
content: OK Thanks one and allThanks in particular for the correction about numbering.QuoteThe Aldi cable does indeed have pins 2 & 5 occupied here. At the telephone side is a 6P2C connector, and that uses the centre 2 pins i.e. (3,4). Therefore, in principle it should still work - It is being "fed from" the correct pins at the master socket I now realise - unless it 'cares about' polarity? (Unlikely I know). Maybe I need to beep-test the cable/check the sprung contacts on the telephone? However, the coincidence that it never worked after the BT visit is hard to ignore.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 01, 2023, 07:02:53 pm
content: If the old phone is working when plugged into the same socket where the new one does not it is difficult not to conclude the problem is with the new phone or its cable. (Phones are not polarity sensitive.)

author: IanB
author_rank: Super Contributor
timestamp: January 01, 2023, 07:11:33 pm
content: Buy a third cheap phone to test with, or borrow one. Make sure you plug the BT plug that came with the phone into the BT socket on the wall. If it doesn't work, you may wish to call out BT to check the wiring.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 01, 2023, 07:18:25 pm
content: It is strongly advised to be as absolutely certain as you can be that any fault is not in the user's equipment of user premises wiring after the master socket. Any callout where the BT line up to the master socket proves to be not-faulty will incur a not insignificant callout charge.