Hard News: The other kind of phone tapping
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I *think* this RadioLab documentary covered, it. Is referred to as 'phreaking'.
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Phreaking is the term. Here's what wiki says:
Possibly one of the first phreaking methods was switch-hooking. It allows placing calls from a phone where the rotary dial or keypad has been disabled by a key lock or other means to prevent unauthorized calls from that phone. It is done by rapidly pressing and releasing the switch hook to open and close the subscriber circuit, simulating the pulses generated by the rotary dial
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I recall accidentally calling 111 using this on our home phone once.
Been a while since I tried, but 999, and 911 also work(ed) to get 111, so once, just mucking around, I clicked 3 times – I assume, with just the right amount of space between the clicks for it to count as 999 – and got a 111 operator.
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jb,
Pre-DTMF days. What we were doing back then was decadic dialling – interrupting the direct electrical current of the phone line thereby generating electrical pulses which the exchange decoded as a dialled digit.
DTMF generators worked the same way later on when things got oh-so-modern... -
And here's why it worked in New Zealand!
In most countries one pulse is used for the digit 1, two pulses for 2, and so on, with ten pulses for the digit 0; this makes the code unary, excepting the digit 0. Exceptions to this are: Sweden (example dial), with one click for 0, two clicks for 1, and so on; and New Zealand with ten clicks for 0, nine clicks for 1, etc. Oslo, the capital city of Norway, used the New Zealand system, but the rest of the country did not. Systems that used this encoding of the 10 digits in a sequence of up to 10 pulses, are sometimes known as decadic dialing systems.
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Yeah, I don't know anything about old rotary payphones but I guess the electric current from the rotary dial was "off" until it detected the right amount of money, so by 'tapping' on the switch hook you're just bypassing that internal lock, the same way prisoners can switch hook to get multiple phone calls during their "one phone call" time or you can use on those old red phones that you used to see in some shops, where your coin literally did just unlock a physical lock on the keypad.
StepDoh, the article you linked to is related to a technique called 'blueboxing', which is where you simulate the noise (remember, PSTN phones are analogue, and so lots of logic/routing is just noises) of the "user just put in 20 cents" (or in the case of US, 25 cents) action, and since for some reason the mic was hooked up to this circuit, that signal would be sent down the line to the automatic operator, which would say "ok, i just heard the money sound, make the call".
Blueboxing worked for a long time in the US. NZ actually has had comparatively modern and secure payphones, at least from the 90s on when I was interested in how they worked...
Had never occurred to me that old switch hook bypass worked though! I never used a rotary payphone. Switch hooking was just something I did at home because I thought it was cool.
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Russell Brown, in reply to
DTMF
I'm going to pretend that stands for DIAL TONE, MOTHERFUCKER.
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Heh! I remember doing this as a kid in the phone box up the road from our house. The hardest part was getting the timing right. Once you had that down pat, free phone calls were yours for the asking.
Mind you, the attraction wasn't that the calls were free -- they only cost a penny or two back then -- and besides, we all had home phones which worked locally for free. It was the fact that we'd aquired this secret knowledge which tricked the Post Office technology which really appealed to us. Boy, were we clever!
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We also knew that you were allowed to dial up to 3 digits (so 111 would work), so you always chose the low numbers to dial. So in your example 584 273 I would have tapped, 5, pause, tapped 2, dialled 4, dialled 2, tapped 3, and dialled 3.
Wasn't it weird how the charge was three 2c pieces ? How awkward was that ? A single 5c, or 10c, piece would have been so much easier. I remember having three 2c pieces in your pocket was one of the things checked on in scouts to show that you were prepared. But I never used them.
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jb, in reply to
That's *exactly* what it stands for....
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also remember those old 4 digit numbers like 1957 and 1949 that would tell you things like the number you're calling from (doesn't work from payphones anymore though) and that one that you could order line tests from, some kind of unsecured contractor automatic service centre thing
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Russell Brown, in reply to
Oh yes. What was the number you could dial to get an automatic call back?
I used that one night at a party to prank a drunk guy (pick up ringing phone, say "It's for you") who turned out to be a psycho violent soldier on weekend leave, and did not see the joke. Until a couple of girls intervened he was seriously going to beat me to a pulp.
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Feeling a strange urge to listen to Wichita Lineman now…
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Ross Mason, in reply to
Mind you, the attraction wasn’t that the calls were free – they only cost a penny or two back then – and besides, we all had home phones which worked locally for free. It was the fact that we’d aquired this secret knowledge which tricked the Post Office technology which really appealed to us. Boy, were we clever!
And when you were out on the piss and thought it would be a good idea to phone partner for a ride, you’d find the nearest phone and “try” and tap the home number!!!! Bugger..repeat…bugger.. repeat..bugger… repeat…..My home number was great but – 286889 was an easy number to phreak……except when you were pissed….
It got very sophisticated when the multi toned frequency system came into the phone system. Many hoons built boxes to gain access to the phone.
See this article that includes the Apple Boys who misspent their youth phreaking in.
Edit: Privacy was always an issue…or the lack of it…especially with the old party lines. Our family regularly moved to phones that had upwards of 6 to 8 people on one line. But we did win at Little River. We had phone number 1.
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There was a phone box in London somewhere where Kiwis in the know could phone home bypassing the coin system and talk free. A queue would form late at night for the privileged few.
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I do know more than a little about this.
The old dial phones would signal the number that was dialled to the exchange by pulsing the line. As the dial wound back to its rest position it would break the circuit repeatedly, at ten pulses a second. In NZ, the mapping was reversed so that the numbers printed on the dial would be in the correct order. (In other countries, the numbers on the dial would read 9,8,7 ...).
One intersting impact of this reversal was the emergency services number : 999 in the UK 911 in the US and 111 here. This was necessary as if we had used 999, it would have corresponded to three lots of one pulse, which could occur due to wind blowing the overhead lines together.
Tap dialling works as the old phone boxes would disable the dial if no coin had been entered, but the hookswitch would still pulse the line. When the hookswitch was down (The handset was on it) the line was in an idle state - it was high resistance and would only respond to ringing from the exchange (which was a high voltage AC signal). When the handset was lifted a resistance was put across the line, allowing a current to flow - around 15millamps was necessary for the exchange to detect the offhook state, supply dialtone, and start listening for dial-pulses.
The machinery used in the exchanges in the 70s and early eighties was really basic. Each pulse would physically cause switches to move to route the call through the exchange. Hence they really only supported dial phones. Later electromagnetic and electronic exchanges would gather the entire number, examine it, and make a decision as to how to route the call. These supported push button phones that signalled to the exchnage using two simultaneous tones (Dual Tone Multi Frequency).
While the old exchanges were slow, basic and high maintennence, they were notoriously robust. You could take an axe to any one part, and the rest would keep on going. (more like a human brain than a modern computer).
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Russell Brown, in reply to
One intersting impact of this reversal was the emergency services number : 999 in the UK 911 in the US and 111 here. This was necessary as if we had used 999, it would have corresponded to three lots of one pulse, which could occur due to wind blowing the overhead lines together.
Wow! And thanks :-)
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IIRC there's a working, cutaway electromechanical pulse exchange at MOTAT where you can dial a number on a phone and watch the workings clunk away selecting the correct line. I could watch that for hours.
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raising the tone…
‘Life’s rich tap history!’The Atlantic had this story…
http://www.theatlantic.com/technology/archive/2013/02/the-definitive-story-of-steve-wozniak-steve-jobs-and-phone-phreaking/273331/
and Phil Lapsley’s book:
http://explodingthephone.com/and more on the 2600hz whistlers and Captain Crunch
http://en.wikipedia.org/wiki/John_Draperhere is the story in comic form by Ed Piskor:
http://boingboing.net/2009/12/20/phreakhacker-history.html -
I totally used to do that as well.
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Kevin et al are correct. The NZ system of having a payphone just disconnect the dial was unusually permissive - in the UK, the exchange knew it was a payphone line and expected some sort of special pulses/tones to indicate money had been loaded before it would connect. The tap-dialing method bypassed the old dial locks, though.
Modems could usually switch between pulse and tone dial using an AT command, so you could use them on a pulse-only circuit. Most PSTN circuits supported pulse until quite recently (I'm not sure if they still do).
Relatedly, in the US the three digit city codes (212 etc) produce less pulses the more important the city, or rather, as Douglas Coupland pointed out, how important the city was in 1955 or so.
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dial elated...
I love the way vestigial concepts remain in the telephonic universe - I still hear messages that say 'dial again' or 'dial this number' or similar - most kids today would never have even seen a dial phone... -
Alst, in reply to
*137 if I remember rightly.
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The one time I remember trying this, some time in my early teens, was in the payphone in Colville next to the Post Office, I couldn't quite get it to work, and then the person working in the Post Office next door came on the line and said "Are you having trouble connecting" or something like that, and I made some sheepish excuse and gave up. I guess Colville was so old-school that the phone box connection still went through the Post Office exchange or something and they could hear or see some evidence that something was up.
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As a pimply teenager in Wellington I used 'tapping' on a pay phone to ring Barry Jenkin in Auckland, during the wee small hours, while he was doing the ZM allnight show.
So it did work for more than local calls.
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