On landlines IIRC there is some feature that allows them to stay on the line after you hang up. So when you try to call the bank, you get the scammers again.
Now that is insane. Totally sounds like one of those things that paranoid old people believe about newfangled technology, but nope, just extremely weird protocol design.
Its not really weird if you look at it in context.
People who are not Gen-Z whipper-snappers will recall the era.
Before cell phones, before DECT home phones, before wireless cordless home phones you had fixed phones.
You had a master socket and then, optionally, one or more secondary sockets (depending where you lived, you were either permitted to install these secondary sockets yourself, or you had to call in the telco to do it).
Anyway, so what would happen is that your friend from school would call you up. Inevitably your parent would answer the phone because they were, for example, in the kitchen cooking your dinner.
There would then be a shout across the house "Bobby its Johnny ... AGAIN !".
The call-transfer process would involve your parent hanging up and you picking up the nearest secondary handset.
Hence the exchange needed to keep the A-end of the call live whilst you completed the B-end "transfer".
The same generation of people will also recall the ability to abuse the mechanism to quietly spy on someone else using the phone. :)
UK analogue strowger exchanges did not permit the called party to clear down the line - that was the job of the calling party. A legacy function of being 'patched through'.
"Called Subscriber Held", a feature that was carried into early digital exchanges because people expected it to work in the manner you describe, even though afaik it was designed for the other purpose of keeping the line open whilst operators patched it through, trunk lines picked up the tone, etc.
My grandpa was a something like chief engineer for the West Coast of Scotland phone network. I have so many questions I wish I could ask him these days.
... although they can hear each other through the devices in their hands. More likely the person in the kitchen just put the handset down on the table and continued cooking.
It's still weird and unnecessary. This happened everywhere, but people just picked up the phone before the other person in the house would hang up. You mention it yourself because of the ability to spy.
Remember it used to be a switched physical circuit. In the early days the switching was done by people, later it was automated. But you still had a circuit from phone to phone.
When one side hung up, the circuit is still live. Eventually it timed out and the switch disconnected it, but it took a while (don't remember how long). So you could hang up a phone, walk to a different room and pick up another phone and the same call circuit was still live (as long as the other side didn't also hang up meanwhile).
It's worth noting that many landline phones now allow you to enter a number that you're intending to call, then pressing the call button at which point the number is automatically dialed.
If the dial tone is heard at all, it is for a very brief period, and might be entirely missed. This would make the scam you're describing even more readily achieved.
... the autodial feature may well be waiting for dialtone in order to dial. I've not looked into this and you're probably best off testing this yourself on your own equipment.
This was, IIRC, a regional thing based on how the internal network was set up And all the legacy stuff. Half the country experienced this and the other half didn't so it always causes fun stories like this And expected gotchas from those who are learning it for the first time.
This also exists (existed?) for mobile numbers, and was used by newspapers to 'hack' certain celebrities' voicemail. Including some cases where they deleted existing messages when the mailbox was full, so they could get more.
I thought they just called their phones when they weren't in and used the default voicemail PIN (which most people don't change) to access their messages.
https://security.stackexchange.com/questions/100268/does-han...
So try to call the bank from a mobile.