I've been told by several people (including a BT engineer) that ADSL can work on just one wire. Whenever I heard this, I thought "Hmm, really?", and not thought about it any more.
It now appears to have happened to one of our lines. The phone is dead, but the ADSL works great. BT say it's a line break, and will take up to two weeks to repair (yes, it's a business line with TotalCare on it - they did respond in 4 hours, but won't be fixing it for a while ;-).
We have two other lines, but they're both ISDN.
So, what's the mechanism that allows me to get 1M down a single wire?