On POTS lines, the call doesn't drop until the initiator hangs up so even if you put down the phone the connection is still there, pick up the phone again and you resume the same call. I used to use this to move to the upstairs phone to continue a call (back then we had two wired handsets on the same line). The last time I can personally cite it working that way is the late 90s, but I'm sure it has more recently than that, possible even still now for some lines.
I can't test as I've not had a voice capable land-line for some time. It may not work on newer exchange equipment. It won't work if you have a service whereby calls are directed over a digital connection. It has never worked for mobile phone services. It doesn't work on some (most? all?) office PBX arrangements, either.
As well as allowing this sort of scam to operate, the "feature" can also be used as a DoS attack, blocking calls to and from a line for a time.
I can't test as I've not had a voice capable land-line for some time. It may not work on newer exchange equipment. It won't work if you have a service whereby calls are directed over a digital connection. It has never worked for mobile phone services. It doesn't work on some (most? all?) office PBX arrangements, either.
As well as allowing this sort of scam to operate, the "feature" can also be used as a DoS attack, blocking calls to and from a line for a time.