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Post by rmc on Nov 4, 2012 19:03:56 GMT
Posted by discoverKrato on November 13, 2011, from DCI (Discovery Channel International) Mythbusters forums:
the myth is that on a land line home phone when you knock the hand receiver off of the dock and tone sound comes on. if you can match your voice to the frequency that the numbers make. the phone will dial the numbers your voice mimics.
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Post by Cybermortis on Nov 4, 2012 19:16:14 GMT
There may be some basis for this. I seem to recall that early computers/fax machines worked by placing the handset in a cradle that used tones to dial numbers and pass on information. So this may be the origin of the 'myth'.
As to if this applies to modern phones I don't know, I suspect not but I'm FAR from an expert.
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Post by freegan on Nov 4, 2012 20:22:34 GMT
I used to work repairing telephone answering machines.
One particularly baffling case was eventually resolved when the fact was noticed that the fault occurred precisely at the same point during the owner's outgoing message.
The vowel sound at that point on the tape triggered the DTMF detector at the exchange, terminating the call.
So yes ... the human voice can mimic at least one tone made by tone-dialing phones and I should imagine, with practice, can mimic all of them.
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Post by watcher56 on Nov 5, 2012 3:53:16 GMT
DTMF tones consist of two separate non-harmonically related frequencies. It would be pretty tough for a human voice to produce those tones. I suspect any case of this actually happening would more likely be the result of a badly adjusted decoder rather than an accurate simulation by voice.
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Post by silverdragon on Nov 5, 2012 6:44:39 GMT
I still own a small hand-held about-the-size of a deck of cards tone dialer....
I have no idea where I got it from....
Anyway, it can store a number of pre-recorded contacts and can be used with most DTMF phones to dial numbers?....
I acquired it when many phones in the UK still had dials, back in the 80's, but the exchanges were accepting pulse and tone dials, so it was supposed to save time with old twist dial phones...
(I am that old.... )
As suggested, the actual tones used are multi-harmonic, I have "heard" that a Parrot had learned the trick, but not a human... I can hum and whistle at the same time, but not hum two separate notes at the same time... you try that?....
Also, I had it somewhere, now I cant find it...
an "App" for them smart phone things....
This app can translate phone-book contacts to sound files and "play" them, thus allowing you to use the speaker to "Tome dial" on a land-line DTMF phone.....
Its that clever that for "Local" contacts it will ask if you need the first 4 digits (UK use).
I was supposed to be keeping that app link in the "Theres an app for that" section on another board, but I forgot to post it there.....
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Post by freegan on Nov 5, 2012 8:01:36 GMT
DTMF tones consist of two separate non-harmonically related frequencies. It would be pretty tough for a human voice to produce those tones. I suspect any case of this actually happening would more likely be the result of a badly adjusted decoder rather than an accurate simulation by voice. Indeed, you're right and, if I cast my mind back, it was during the time that the UK was in the process of switching over to digital exchanges. Therefore, it's almost certain that the DTMF decoders kludged onto analog exchanges were pretty rudimentary and accepted not-too-close matches to digitally generated DTMF tones. To correct my previous answer; A human voice could, once, have been misinterpreted as DTMF but the tighter error margins on modern digital exchanges make it highly unlikely that this could be possible today. I still own a small hand-held about-the-size of a deck of cards tone dialer.... I have no idea where I got it from.... They were frequently part of the package with remote controllable answering machines and allowed the user to retrieve messages from remote locations (among other functions) provided you could remember your remote access code and the instruction codes (although yours sounds a little fancier than the ones I encountered). They were soon superceded by remotes pre-coded to each machine and, later, answering machines were superceded by answering services provided by the digital exchange. |
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Post by Lonewolf on Nov 6, 2012 13:43:49 GMT
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Post by The Urban Mythbuster on Nov 8, 2012 16:51:26 GMT
Steve Jobs once found a way to outsmart payphones: "In the early 1970s, Jobs and Wozniak were drawn to technology like a magnet. Wozniak had designed a low-cost digital "blue box" to generate the necessary tones to manipulate the telephone network, allowing free long-distance calls. Jobs decided that they could make money selling it. The clandestine sales of the illegal "blue boxes" went well, and perhaps planted the seed in Jobs's mind that electronics could be fun and profitable Read more: www.answers.com/topic/steve-jobs#ixzz2BeOyCm3D" |
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Post by GTCGreg on Nov 8, 2012 17:26:41 GMT
To answer the OPs question, yes, you could mimic the tones used for dialing. The problem is that, unless you had a very unusual talent, it would take two people. One for the row tone and one for the column tone.
Another interesting tidbit. You could also dial numbers by just tapping the switch hook the number of times corresponding to the number you wanted to dial. For example, if you wanted to emergency dial 911, if you tapped the switch hook nine times followed by a short wait and then one time and another one time the call would go through to 911. This was how the old rotary dial phones sent the numbers. I don't know if all current phone systems still support dial phones. Also, on some of the newer electronic phones, the switch hook doesn't directly connect to the phone line.
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Post by c64 on Dec 10, 2012 17:39:55 GMT
Those handheld DTMF encoders usually came with a state of the art answering machine allowing you to make it play your messages if you call it from a rotary dial phone. I have one of the first answering machines available. A box you can put your phone onto which contains a magnetic drum. When there is an incoming call, the drum rotates and plays the message you had recorded on it. The magnetic head sits on a wormgear and can record up to 15 minutes moving along the spinning drum. When the beep is played from the drum, it unlocks the magnetic head which is pushed into its starting position by a spring. The high pitched beep played by the drum at the end of your message then activates a relay powering up an electric outlet which energized an optional "dictaphone" to record the message of the caller. I didn't had one of those compact dictaphones but I used a big reel to reel tape machine capable to record 18 hours ofr messages. The low pitched beep from the drum made the machine drop the call. This is the origin of the "Please leave a message after the beep" since the beep was part of the recording and either made the machine drop the call "Please call again during office hours *beep* *click*" or made it record a message. Also the machine couldn't know how long the message is it has to play. To answer the OPs question, yes, you could mimic the tones used for dialing. The problem is that, unless you had a very unusual talent, it would take two people. One for the row tone and one for the column tone. Another interesting tidbit. You could also dial numbers by just tapping the switch hook the number of times corresponding to the number you wanted to dial. For example, if you wanted to emergency dial 911, if you tapped the switch hook nine times followed by a short wait and then one time and another one time the call would go through to 911. This was how the old rotary dial phones sent the numbers. I don't know if all current phone systems still support dial phones. Also, on some of the newer electronic phones, the switch hook doesn't directly connect to the phone line. Dialling with the hook did work with the early step-by-step switches in the branch exchanges. The more modern stainless steel rotary diallers were much more picky with the timing and stopped taking impulses if you were too slow forwarding the rest of your number to the next one or didn't turn far enough so it dialled a "8" instead of a "9" or something like that. You have to be very skilled to dial long numbers. It's possible (I can do that) but many people just can't. Fun fact: In Germany, the emergency number for the police used to be "111" and the number of the fire brigade is "112". But since tapping the hook like seen in the movies when the hero discovers that the telephone is dead can dial ones easily so the police had changed their number to "110" which is impossible to dial with the hook by accident. That stopped people who tried to fix their phone by hammering it with their fists call the police by accident. And by the way, it wasn't Steve Jobs who discovers blue boxing and stuff. He was a marketing guy and never had much knowledge in electronics. He just happened to find brilliant friends and did the marketing for their inventions. Tampering with the phone system was discovered by a blind friend of John T. Draper discovering that there were inaudible whistling tunes in the phone system and that the whistle which came with "Cap'n Crunch" cereals played one of the tunes. That's why John T. Draper is now known as "Cap'n Crunch", he's the famous hacker who invented "blue boxing" by creating a box that emitted this special tune as the cereal gift whistle. This was the start of all those "Color boxes" like - red box for public pay phones - aqua box to prevent that the authorities can identify the line you were calling from - rock box to inject music into the phone system you can hear from millions of phones by just picking up the receiver and many more. |
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