Thank you Keith_Beddoe and Liquorice for your further replies.
I'm still a little unsure about which cores to connect to A/B.
Here's a closer pic of the socket for my modem/router's RJ11 plug:
Using my awesome MSPaint skills I've annotated where the RJ11 and CAT5/6 enter the device.
I'm not sure what the blue A signifies. But, if I wire a CAT5/6 cable into this device, which 2 cores am I connecting to A/B?
Sorry for all the questions guys - I just want to get this clear before I start drilling through walls!
Thanks in advance
I'm not familiar with that device, but the RJ11 only needs the 2 centre pins connecting to the A&B in the NTE. With a normal 6P2C plug the pins would be 3&4 but with 8P2C I'm not sure but would think it would be 4&5 i.e the solid green and the blue stripe. Don't use those coloured wires though as they will not be a pair and will be susceptible to interference. Use the blue blue/white pair in the cable.
If you want to leave the router where it is, you could run ordinary CW1308 cable from the internal two connections off the BT faceplate and terminate them in a RJ11 outlet socket. Then you just need to plug your routers RJ11 plug into that. Or..leave the router where it is and run a CAT5e cable from the LAN connection either port 1-4 is ok on the router and terminate that in a RJ45 modular socket. Terminate all 8 wires colour to colour. You can install a RJ45 socket both ends (easier than fitting RJ45 plugs) and then use standard patch leads to hook the sockets to the router and then the PC direct.
Useful advice but I guess the OP is sorted as the last post on the thread was 18 months ago.