[russell_w_b]

Jake,

Have you any extension telephone sockets?

I suspect that the two wires leading to terminals T1 and T4 of your bell are connected to terminals 3 and 5 of either your 'master' socket or any one of your slave (extension) sockets - if you have any.

Without getting too previous, and to keep your system 'universal' (ie: suitable for use with other converted telephones you might acquire), if you adjust the wiring links in your N1071 as per my diagram in post #1 (apart from fitting a standard BT plug and lead, which may not be necessary) you will be in a position to connect it - and the bell - to the system. And if you wish to keep the extension bell 'paired' with your N1071, it would be possible to connect the bell directly to the N1071 via 'hard wiring' in lieu of the 3k3 resistor.

Before going further and to save confusion, it would be a good idea if you could trace the wire at your bell back to where it connects to your system and tell us to where the coloured cores are connected, and whether the green and brown unused cores are present and able to be used.

Have you a multimeter?