4 ms·

Also, don't call from the same phone you received the call on, if on a landline. One time (I can't find the reference) scammers called from the bank, suggested

Also, don't call from the same phone you received the call on, if on a landline. One time (I can't find the reference) scammers called from the bank, suggested the person called back to the number on their credit card. The person hung up, picked up, and the scammers had held the line, played a fake dial tone, and had someone else "pick up".

IIsi50MHz 3y ago
In USA telephones, unless you timetravel to "party lines" (when sets of local numbers had the same line, so picking up while a call was in use allowed people to listen or join in), hanging up any one end of a line disconnects the call the departing user from the call. If the described scam happened, in should have required a simultaneous fault in the phone system. Or more likley, the scammer played a recorded sound of a disconnect+dialtone, which could tricker the target into dialing.
- toast0 3y ago
  The time required for a good hangup might vary a little bit from exchange to exchange. I recall occasionally being able to transfer to different handsets hanging up one before picking up the other. But not to the extent reported in some anecdotes where one end can hold the call open indefinitely.
  - jjnoakes 3y ago
    This is definitely true. I remember being able to quickly press and release the hangup button on a single phone and if I was quick enough the other person would remain on the line. I don't recall exactly where the threshold was, but I believe it was around a half a second or so.
    - ThinkingGuy 3y ago
      I remember being able to hang up the phone in one room, run to the next room, and pick up the phone and continue the conversation. My friends and I did this on several occasions. This was in the Atlanta area, in the late 1980s.
    - eep_social 3y ago
      Rapidly pressing and releasing the hang up button simulates pulse (as opposed to tone) dialing used by rotary phones.
- aidenn0 3y ago
  This is incorrect at least on Bell Atlantic's (and then Verizon's) network in the late 90s. Since there is no double-billing on landlines in the US, the person initiating the call is the only one that can immediately terminate a call to a landline. There's a timeout for the reverse direction, but it at least used to be fairly long. Someone pulled a trick where they took advantage of this. Had a friend call and keep the line open. Then claim that you have the entire phone book memorized. To prove it, ask someone to name a random name, punch in 7 digits and hand it off to the person who named it. They ask for the name and your friend says "yes that's me" (or "they're not home now if the gender mismatches).
  - techsupporter 3y ago
    > There's a timeout for the reverse direction, but it at least used to be fairly long. This brings up one of those cultural things: ever noticed how in movies and TV shows from the 80s and 90s, if the caller hung up, the person called immediately got a dial tone? It's a trope that prop wranglers, set designers, and writers picked up because the telephone company around Los Angeles (Pacific Bell) had switches that would reset the line state for the destionation back to "ready for call", which meant dial tone, when the origin side disconnected. If the destination side disconnected, the origin would only be disconnected after approximately 20 seconds. Almost all other exchanges would put the destination--after the origin disconnects--into an off-hook-but-not-ready and then, after 10 or so seconds, play the "if you'd like to make a call, please hang up and try again" recording, then Special Information Tones, then a rapid busy. Yet because the service in and around LA is what a lot of people in the TV and movie business experienced, it is what got baked into those productions.
    - aidenn0 3y ago
      > rapid busy I was a rather violent sleeper when I was young and would occasionally knock the phone off the hook while sleeping. Then I woke up to the fairly loud rapid busy sound. Hadn't thought about that a while.
    - TheKarateKid 3y ago
      Interesting. I always assumed that the immediate dial tone after origin disconnected in movies & TV was for dramatic effect to let watchers know that the person hung up the phone.
- NoZebra120vClip 3y ago
  IIRC, the originating party's on-hook will immediately disconnect the call, while if the receiving party goes on-hook, there is a short but significant delay before disconnect is finalized. This may have something to do with service offerings such as call-waiting and 3-way, which depend on detecting a "flash" signal.
dudul 3y ago
What? Where do phones work like that? Isn't it enough for one party to hang up for the call to be over?
- ralferoo 3y ago
  They used to operate this way in the UK - the line would stay occupied until the call initiator hung up. We used to play with this when I was a kid, but I've not had a landline since early 2000s, so I've no idea if this survived the transition to digital exchanges. TBH I doubt it, and I know lots of people complained about it, because it was really annoying if someone who'd called you hadn't hung up properly as then you couldn't make any further calls yourself.
Mordisquitos 3y ago
I believe that potential exploit only work(s|ed) in the UK telephone network, and maybe those of countries developed in parallel using similar technology. Either way, it is a zero-cost precaution so you might as well do it just in case.

IIsi50MHz 3y ago

In USA telephones, unless you timetravel to "party lines" (when sets of local numbers had the same line, so picking up while a call was in use allowed people to listen or join in), hanging up any one end of a line disconnects the call the departing user from the call. If the described scam happened, in should have required a simultaneous fault in the phone system. Or more likley, the scammer played a recorded sound of a disconnect+dialtone, which could tricker the target into dialing.

toast0 3y ago
The time required for a good hangup might vary a little bit from exchange to exchange. I recall occasionally being able to transfer to different handsets hanging up one before picking up the other. But not to the extent reported in some anecdotes where one end can hold the call open indefinitely.
- jjnoakes 3y ago
  This is definitely true. I remember being able to quickly press and release the hangup button on a single phone and if I was quick enough the other person would remain on the line. I don't recall exactly where the threshold was, but I believe it was around a half a second or so.
  - ThinkingGuy 3y ago
    I remember being able to hang up the phone in one room, run to the next room, and pick up the phone and continue the conversation. My friends and I did this on several occasions. This was in the Atlanta area, in the late 1980s.
  - eep_social 3y ago
    Rapidly pressing and releasing the hang up button simulates pulse (as opposed to tone) dialing used by rotary phones.
aidenn0 3y ago
This is incorrect at least on Bell Atlantic's (and then Verizon's) network in the late 90s. Since there is no double-billing on landlines in the US, the person initiating the call is the only one that can immediately terminate a call to a landline. There's a timeout for the reverse direction, but it at least used to be fairly long. Someone pulled a trick where they took advantage of this. Had a friend call and keep the line open. Then claim that you have the entire phone book memorized. To prove it, ask someone to name a random name, punch in 7 digits and hand it off to the person who named it. They ask for the name and your friend says "yes that's me" (or "they're not home now if the gender mismatches).
- techsupporter 3y ago
  > There's a timeout for the reverse direction, but it at least used to be fairly long. This brings up one of those cultural things: ever noticed how in movies and TV shows from the 80s and 90s, if the caller hung up, the person called immediately got a dial tone? It's a trope that prop wranglers, set designers, and writers picked up because the telephone company around Los Angeles (Pacific Bell) had switches that would reset the line state for the destionation back to "ready for call", which meant dial tone, when the origin side disconnected. If the destination side disconnected, the origin would only be disconnected after approximately 20 seconds. Almost all other exchanges would put the destination--after the origin disconnects--into an off-hook-but-not-ready and then, after 10 or so seconds, play the "if you'd like to make a call, please hang up and try again" recording, then Special Information Tones, then a rapid busy. Yet because the service in and around LA is what a lot of people in the TV and movie business experienced, it is what got baked into those productions.
  - aidenn0 3y ago
    > rapid busy I was a rather violent sleeper when I was young and would occasionally knock the phone off the hook while sleeping. Then I woke up to the fairly loud rapid busy sound. Hadn't thought about that a while.
  - TheKarateKid 3y ago
    Interesting. I always assumed that the immediate dial tone after origin disconnected in movies & TV was for dramatic effect to let watchers know that the person hung up the phone.
NoZebra120vClip 3y ago
IIRC, the originating party's on-hook will immediately disconnect the call, while if the receiving party goes on-hook, there is a short but significant delay before disconnect is finalized. This may have something to do with service offerings such as call-waiting and 3-way, which depend on detecting a "flash" signal.

dudul 3y ago

What? Where do phones work like that? Isn't it enough for one party to hang up for the call to be over?

ralferoo 3y ago
They used to operate this way in the UK - the line would stay occupied until the call initiator hung up. We used to play with this when I was a kid, but I've not had a landline since early 2000s, so I've no idea if this survived the transition to digital exchanges. TBH I doubt it, and I know lots of people complained about it, because it was really annoying if someone who'd called you hadn't hung up properly as then you couldn't make any further calls yourself.

Mordisquitos 3y ago

I believe that potential exploit only work(s|ed) in the UK telephone network, and maybe those of countries developed in parallel using similar technology. Either way, it is a zero-cost precaution so you might as well do it just in case.