I am in the UK.
I have a Virgin Media/NTL landline and am considering installing a BT landline too. (I need Caller ID but VM/NTL don't have it in my area).
If I have answered a call on VM/NTL and also on BT then how can I join the two lines to have a 3-way conversation?
Is there a circuit I can build which will join the two lines?
(1) Perhaps picking up the signals by a transformer across each of the two line cords?
(2) Perhaps across each curly lead which goes from handset to phone?
(3) Would I get better results "audio-coupling" the handsets. Holding one earpiece close to the other mouthpiece and vice versa?