Author Topic: Does 'Called Subscriber Held' Still Exist?  (Read 1025 times)

bellsystem

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Does 'Called Subscriber Held' Still Exist?
« on: July 19, 2017, 02:32:48 PM »
I was just reading about a phone scam in the UK that utilizes CSH and was surprised that it still exists. I know that when SxS switches were the norm, only the calling party could disconnect a conversation. The called party could not; they were free to hangup and pick up again and continue.

This is demonstrated somewhat in this video: https://www.youtube.com/watch?v=bUIiUXvnkUQ
(That video also talks about why you hear a dial tone when you hang up in California, et al. - does anyone still get a dial tone when they hang up??)

Here is a clip that shows EXACTLY what I'm talking about: https://youtu.be/qgjqyiSMyJk?t=406
(watch from 6:46 to 10:15)

At first, I thought it would be annoying to have something like this in 2017, but when you consider the quirky benefits, it's really a mixed bag. Are there any landline providers that still offer this "feature"?

Also, was this really because of the "lack of far-end supervision" as the first video claims? Were SxS exchanges literally not physically capable of detecting if the called party was on or off hook?
« Last Edit: July 19, 2017, 02:43:36 PM by bellsystem »

Offline twocvbloke

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #1 on: July 19, 2017, 05:55:01 PM »
Yeah, the CSH scam is quite common in the UK, for those that don't know it, it's basically when a scam artist calls your number, announces themselves as your telephone provider (Plusnet, TalkTalk, EE, Vodafone, Sky, etc.) or generically as "British Telecom" or "BT" and claim your bill is overdue and that you will be disconnected if you didn't pay there and then, and when the callee questions this, the scammer informs them that they can switch the line off if they hang up, and the callee hangs up, but the scammer just mutes their phone to give the impression of a dead line, they hear the callee pick up the phone to check and hang up again, then the scammer hangs up, calls back and proclaims that they disconnected the line to show it was really your phone provider, then the callee either lets them know "Yeah, I've heard of this scam before, goodbye!", or, sadly, ends up handing over financial details and lose their money...

I hope they try it with me someday, got a nice selection of obnoxiously deafening tones I'd thoroughly enjoy playing down the phone through their headset...  ;D

Alex G. Bell

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #2 on: July 19, 2017, 07:10:30 PM »
I was just reading about a phone scam in the UK that utilizes CSH and was surprised that it still exists. I know that when SxS switches were the norm, only the calling party could disconnect a conversation. The called party could not; they were free to hangup and pick up again and continue.

This is demonstrated somewhat in this video: https://www.youtube.com/watch?v=bUIiUXvnkUQ
(That video also talks about why you hear a dial tone when you hang up in California, et al. - does anyone still get a dial tone when they hang up??)

Here is a clip that shows EXACTLY what I'm talking about: https://youtu.be/qgjqyiSMyJk?t=406
(watch from 6:46 to 10:15)

At first, I thought it would be annoying to have something like this in 2017, but when you consider the quirky benefits, it's really a mixed bag. Are there any landline providers that still offer this "feature"?

Also, was this really because of the "lack of far-end supervision" as the first video claims? Were SxS exchanges literally not physically capable of detecting if the called party was on or off hook?
Call release depends on a number of factors such as whether the call is local or a toll.  The sound is so poor on the Hazel video that I cannot understand what's going on.  This problem occurs watching it in a browser or downloading and opening it in either of two viewers.

It's absolutely untrue that there was no answer supervision from the called end.  Answer supervision is required to control charging of the calling customer and always was returned in any PSTN environment.  Only PAXs (isolated intercom systems using conventional public exchange telephone switching technology) lacked answer supervision because it is pointless in a PAX.  Even PABXs returned answer supervision both for internal calls and incoming calls from the CO to an extension.

In common control offices (Panel, XB, ESS) even if the called end were SXS, the originating end CO would release the connection approx. 20 seconds after the called party hung up. 

If the calling office were SXS and the called was common control the terminating office would release the called line after ~20 seconds. 

For most any toll call the toll office would release the connection after time out if the called hung up. 

So the only case where the caller could hold the called line indefinitely would be a local call within a SXS office or between nearby SXS offices when there were SXS offices, more than 20 years ago now, or between two EXTs in a SXS PABX (an internal call).


Offline TelePlay

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #3 on: July 20, 2017, 11:06:18 AM »
I was just reading about a phone scam in the UK that utilizes CSH and was surprised that it still exists. I know that when SxS switches were the norm, only the calling party could disconnect a conversation. The called party could not; they were free to hangup and pick up again and continue.

Here is a clip that shows EXACTLY what I'm talking about: https://youtu.be/qgjqyiSMyJk?t=406
(watch from 6:46 to 10:15)

First, yes, this could be done for minutes at a time. I had someone hang up on me in the early 90's but I stayed online and when they picked up the phone 3 minutes later, the line was still connected. I did not get a dial tone when they hung up so I knew the connection was still in place. But that was 25+ year old CO equipment. Today, you would need two land lines to test this. Can't test it on modern telephony. With the high demand for bandwidth, be it fios or PCS, as soon as one party hangs up, the other party may hear a computer generated click of the hang up, then a dead line for 10 or so seconds and then some sound track, a busy or other signal to hang up that phone.

Second The first clip is a good example, if you know how to unwind what is being said, saying in the old days with SxS systems, the called party would stay connected and only the caller could disconnect the call, as above. The first clip also ducked and bobbed around the point that directors, screenwriters and sound editors were the people, the reason of how a phone call "sounded" once the final version was edited and canned for distribution. And, again, those were not live conversations on real phones. Each actor was filmed, probably in more than a few takes, until the director liked what he had on film. It was then up to the video and sound editors to cut and splice all that together, based on the writers story board, to make the conversation "seem" real when viewed as a video creation - big screen or TV. Nothing on film is real. Three days of the Condor had many phone calls, all on dead phones with each phone scene shot more than once. Using such video clips to prove a point is pointless in that they are fake.

Third, That Hazel clip was just that, was nothing more than stagecraft. That was not a real conversation in real time on real phones. They took a camera to the phone booth and recorded all the action and voice on a dead phone. A few days later, they went into the sound studio and recorded the wall phone segments with one camera on a dead phone. Some video and sound editors put it all together to seem like a real telephone conversation. It was fake as was the hang up and non-disconnect.

I can tell you from first hand experience that actors do not like having to say their lines while having to listen to anything in the receiver of the phone they are using on stage or in front of a camera. It distracts them from acting. Those were dead phones shot with one camera on different days. Not a real example of CSH.

Rather than relying on faked videos, it would be best to have comments made from real, present day experience with anything like this as twocvbloke did in a factual presentation based on real life experiences. Or as I did in that early 90s example. This forum is about real things,not hypothetical ideas or events supported by created theatrical effects.

Extract the two paragraph from the first topic that relate to Hollywood phones and the rest of the topic stands as a good question, of which the answer is, yes, it can, but it depends on the phone system being used for a particular call and there are hundreds of thousands or switches out there today built from many different phone system technologies, many of which will not allow CSH that to happen but a few older systems that might allow that today.

I think the question in the first paragraph, less the Hollywood themes, has been answered quite well in the above replies (not mine) in two words,"it depends."
            John . . .

              

bellsystem

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #4 on: July 20, 2017, 11:41:43 AM »
The videos demonstrate what I am talking about - I am not using them to support anything. But they definitely provide a good idea as to what exactly I'm talking about and in what scenarios things like this would happen. They wouldn't have filmed it that way if the public could not relate to it like that.

Offline TelePlay

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #5 on: July 20, 2017, 01:28:37 PM »
The videos demonstrate what I am talking about - I am not using them to support anything. But they definitely provide a good idea as to what exactly I'm talking about and in what scenarios things like this would happen. They wouldn't have filmed it that way if the public could not relate to it like that.

It's fictional support and having worked in theater for over 20 years, I must say that the least important part of a play or movie or TV show is the reality of a sound or group of sounds. Sound is used to support a scene. The most important part of any movie, TV show or play is how the actor makes the people viewing the creation feel. Not what they say, but how what they say makes the audience feel. There is not sound or sequence of sound events that make a theatrical production better. Without them, something would seem to be missing but the sound creation is at the direct desire of the director, it's his show. He could care less about how it "really" is versus how the chain of events supported by the sound makes the audience feel.

And, I think most members 1) know what you meant and 2) feel as if they wasted their time having to watch YouTube videos of fictitious phone operation which explains what they already knew. Factual videos of obsolete phone equipment operations are not found in TV shows or movies.

The Bell archives and a few other historical sites may have some videos made when the now obsolete systems were brand new, state of the art, explaining the "new" features but anecdotal similar events of such operations created on "film" to entertain an audience for ratings (money) is not one of them.
            John . . .

              

Offline Owain

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #6 on: July 21, 2017, 03:21:29 PM »
More often the victim is called by "their bank security" and is told to call their bank. The scammer then holds the line and plays fake dialtone while the victim hangs up and then dials their bank's number. The scammer then pretends to be the bank and asks the standard security questions, so obtaining the appropriate responses for use later.


bellsystem

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #7 on: July 21, 2017, 03:23:58 PM »
Isn't there a way to determine if the dial tone you are hearing is provided by the CO or by someone else on the line?

In other words, is there a way to detect if you're line is connected to anything else? Or is this impossible to avoid from a technical standpoint?

Offline twocvbloke

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #8 on: July 21, 2017, 03:31:59 PM »
Isn't there a way to determine if the dial tone you are hearing is provided by the CO or by someone else on the line?

In other words, is there a way to detect if you're line is connected to anything else? Or is this impossible to avoid from a technical standpoint?

In theory, if you suspect that the dial tone isn't the real deal, you can dial a number you know goes somewhere else (mobile, friend's number, or even the BT test facility, which is 17070), if it doesn't go through to where you expect it to, then it's a false tone, but, unless someone is savvy enough to pick up on such scams, people will automatically assume it's the real tone...

The other option is to use a mobile number for banking, can't hold a call open on those... :)

bellsystem

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #9 on: July 21, 2017, 03:37:16 PM »
Yeah that's true, I could always dial a number I know will do something particular.

But using a mobile phone for banking is about the most insecure thing you could do. Banks recommend you don't even use cordless phones for banking.

Offline twocvbloke

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #10 on: July 21, 2017, 03:41:54 PM »
Personally I just use the internet for banking, never used telephone banking, and if I need to speak t the bank, I find of any are left open nearby (my bank keeps closing branches) and pay a visit in person... :)

Offline Owain

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #11 on: July 21, 2017, 07:54:27 PM »
Yeah that's true, I could always dial a number I know will do something particular.

Given time I expect the scammers will add DTMF recognition to their fake dialling tone, and pass the call through. That's where those LD phones might come in handy!

In the UK the way of breaking CSH is to send a time-break recall (hook flash) and then hang up. The exchange will ring the line back for about half a minute, then disconnect the call if the ringback is unanswered.


But using a mobile phone for banking is about the most insecure thing you could do. Banks recommend you don't even use cordless phones for banking.

The early cordless phones had no security for voice; DECT is reasonably secure but does have known vulnerabilities. A DECT phone is still harder to tap than an analogue phone line.

A standard 'dumb' mobile phone that's unlikely to be running compromised software is probably the most secure means of communication available to the general public without technical knowledge. VOIP could be encrypted, but I don't see any banks offering encrypted incoming SIP connections - most of them still don't even use email when encyption for that has been available for decades.

bellsystem

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #12 on: July 21, 2017, 08:46:38 PM »
You need physical access to a landline to tap it.

And DECT phones would be using the line anyways, so no matter how secure a device using the line is, the communication is only as secure as the line itself.

What do you mean by "LD" phones? Long distance phones?

In the US, does flashing work? I flash a lot on the PBXs and have figured out how that works, BUT on the Panasonic PBXs, if you're on a call and flash the switchhook, then hang up, when you pick up, you are RECONNECTED with the original party (before you flashed). So I don't know what that would really do for you. You could flash the switchhook when you're on the call, get second dial tone, and then dial the number. I think that would be foolproof, right?

Offline twocvbloke

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #13 on: July 22, 2017, 06:18:39 AM »
What do you mean by "LD" phones? Long distance phones?

LD = Loop Disconnect, aka Pulse Dialling...

Offline Owain

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Re: Does 'Called Subscriber Held' Still Exist?
« Reply #14 on: July 22, 2017, 06:22:23 AM »
What do you mean by "LD" phones? Long distance phones?

Loop disconnect.


In the US, does flashing work? I flash a lot on the PBXs and have figured out how that works, BUT on the Panasonic PBXs, if you're on a call and flash the switchhook, then hang up, when you pick up, you are RECONNECTED with the original party (before you flashed).

In the UK if you press recall on an exchange call you get dialling tone and are then expected to dial a code for conference call etc. If you hang up the exchange will ring your line with your existing call. However there is a timeout on that if you don't answer, after which the existing call will be cleared down.