[tomxor]

> I read about a landline attack that would keep the line open when you put the receiver down

I experienced this once, but not as a scam, I think there must have been some kind of fault at the exchange... the other end was a mobile phone and they didn't end the call, just putting the phone back in their pocket - the landline wouldn't disconnect, whatever signal was send, even disconnecting the phone entirely and plunging it back in. I didn't understand how exactly, but it made it pretty clear the (landline) telephone is not in control of the connection.