I recall a time when DJs tried to get the phone to dial the number at the beginning of Billy Joel’s “Sometimes a Fantasy” song (which has touch tome sounds in the opening) by asking listeners to hold the phone up to the speaker. Is there any truth in this? Or, better yet, can one touch tone phone (on speaker) dial another phone if the receiver of the latter is held near the speaker of the former? - Jinx
Yes. That’s how touch-tone dialing works, except it’s the phone itself generating the tones when you push the buttons. It makes no difference if you generate the tones from another source, and simply hold it up to the microphone on the handset.
I have heard that some people can actually whistle the tones, and dial that way. I’m not really sure if that’s true, but it’s technically possible.
Acoustic couplers allowed early computer modems to connect to the phone network - they simply consisted of a speaker that you placed the handset’s microphone next to, and a microphone you placed the handset’s speaker next to. The computer would generate the appropriate frequencies on the speaker.
True-some folks can/could whistle with perfect pitch to duplicate DTMF.
This article has more information.
Long, long ago-shortly after the earth’s crust cooled and there were no cell phones, I carried a pager-sized device in my briefcase which was held to a rotary dial phone’s mouthpiece so DTMF tones could be entered to access directories at the home office and activate other tone-controlled devices such as remote retrieval answering machines.
And for those of us who are REALLY old, Mork would always dial phones that way. 
-Joe
I remember as a kid, “phone phreaking” was a big thing. IIRC, it had to do with gaining access to a phone company’s internal line through which one could dial long distance for free. I don’t really understand the details, but there were computer programs called Black Boxes you could get from Pirate BBSs that replicated normal and special telephone tones, and you could play these tones by holding your telephone up to the computer speakers, and by using these, you could bypass the normal telephone routing systems. Also, at one point, a free whistle given out in Cap’n Crunch cereal emulated a secret tone perfectly. So to answer your question, yes, it is possible.
you can read more about this here, it’s very interesting:
Where in that article does it say that someone is able to whistle the DTMF sounds? I think you may be confusing that with the old signalling tones that phone phreaks used to be able to produce to get free long distance (e.g. the “Captain Crunch” whistle). I find it hard to believe that there is anyone that can whistle in two different frequencies simultaneously (which you would need to do to duplicate DTMF).
Yep. In fact, there were products out in the 80s and early 90s that I recall were designed to allow you to dial a number on the phone without touching its keypad. Apart from not having to touch the germy keypads on public telephones or needing to dial out on a phone with a broken button or two, I couldn’t see much point.
I had an Atari Portfolio back in the early 90s, and it had a built-in DTMF tone generator for external phone dialing.
When I was in High School, we had a guest performer in the auditorium who could whistle in harmony. It was sufficiently entertaining to keep us in our seats for a 45 minute presentation. So yes, some folks can do it. But I’d assume it’s a rare talent.
I’m not sure if this counts, but I can hum and whistle as the same time, and it creates a strange dual tone whistle that I can make sound like a phone tone. I’m not sure if this is the same thing as what you are talking about. Can someone out there try what I am describing?
I understand from telephony experts I once had come to know that the touch tones you hear are actually three tones superimposed to sound (to the human ear) as one tone. - Jinx
You are confusing the 2600Hz, single tone once used by the phone companies for internal switching (not dialing) with the Dual Tone Multi-Frequency (DTMF) tones used for dialing.
It would be extremely difficult to reproduce two different pitches simultaneously with the voice and stay within the required parameters of pitch, loudness and duration. And that would only code for a single digit.
See this thread for more info, especially post #34 and following.
No, TWO. That’s why it is called DUAL Tone, not TRIPLE Tone.
http://nemesis.lonestar.org/reference/telecom/signaling/dtmf.html
Check out the specs I linked to in my previous post. While what you describe is theoretically possible, it would be hard to ensure that the tones were loud enough, similar enough, and pure enough, not to mention duration and within a very narrow pitch range.
If you listen to your phone while you press the digits, you can hear that the audio is blanked out and the tones are sent thru the line at a very high level. Without the blanking, extraneous audio would confuse the issue and without the high level (which I believe is not obtainable by shouting into the mic due to limiting), the digits would not be recognized or decoded correctly.
HOWEVER, it appears that that given enough random samples and sloppy enough equipment, some sounds can be interpreted as digits, probably not reliably enough to dial a complete phone number:
Acoustic modems/couplers have nothing to do with touch tone dialing or even the concept of. Acoustic couplers are an early version of a modem, which translates digital data to analog, sends that over the analog phone lines, then reverses the process at the other end.
They were invented because in those days, not only were phone jacks not common, but Ma Bell was paranoid about anyone connecting a wire to their circuits, claiming all their linemen would be knocked off the poles with shock if anyone did that. So the acoustic modem got around the need for a direct connect with an indirect one; a signal no more dangerous than voice or music.
The signals sent thru the phone lines of a typical modem (acoustic or otherwise) are called FSK - Frequency Shift Keying, two tones that alternate (not simultaneous). From this:
This system has nothing in common with DTMF. The frequencies alone are totally different.
I’ve probably contributed too much to this thread already, but if I don’t say it, someone else will.
Yes, I know that not all modems use FSK, or even PSK or QAM. But for the purposes of this thread, they are similar but quite different from DTMF.
And, more directly to the OP, yes, it is possible to send DTMF tones thru the acoustic part of a telephone mic to get a number dialed. There used to be pocket gadgets that stored your personal phone book and could dial any number by holding the gadget up to the phone mic. I never owned one, but I have seen them used.
However, this is possible due to the frequencies and other specs matching the requirements. The only difference was the acoustic coupling, which didn’t distort the signals enough to make them unrecognizable. If you played back a recorded DTMF sound, it would have to be loud enough and separated from ambient noise to work well. Playing a record across the room probably wouldn’t work but putting the phone up to a loud speaker might.
Simulating the tones with a voice would be a lot more difficult and iffy.
Why don’t you test it yourself? Pick up a phone, and try to “break” the dial tone. If you produce a signal that telco thinks is a valid DTMF digit 0…9, the dial tone will stop immediately.
Hey – this topic would be a good “Ask Cecil” column!
I seem to recall a bit of a to-do some years back, with one of those “Talk to Santa” 900 number things you see advertised during kids shows. The ad told kids that if they held the phone up to the TV while the commercial was playing, it’d magically dial the number. Of course, it also told kids to not do this without their parents’ permission, but you can imagine how many children listened to that part.
I can whistle and hum different notes at the same time. I’m pretty sure I could train myself to vocally produce at least the easiest of the DTMF tones (the one that represents the digit 1).
It consists of 1209hz, which sounds like this, which is comfortably within my whistling range, and 697Hz, which sounds like this, which I’m sure I could hum (except not right now, as I have a cold and it’s gone to my chest and throat).
Combined, the two frequencies sound like this.
In fact, they were quite handy for for phone customers who still had the old-style pulse dialing lines. You’d dial your bank-by-phone number the with the traditional pulse dialing, then use your nifty touch tone dialer to access your account.
I don’t know if any phone companies in the U.S., even still offer pulse-dialing lines anymore.
I’ve seen a couple of movies/tv shows where someone “dials” a number by clicking the receiver in such a way as to simulate a pulse dial. Does this really work?
Yup, it was called “tap dialling” and we used to do it when I was a kid - just for a while before DTMF came in. My dad claims that in the '60s you could circumvent some coin-operated payphones by tap dialling instead of using the dial. I guess they fixed the dial in place mechanically or something.
He also says that you could dial into an exchange then dial out again immediately before the relays clicked into place, and if you knew the number of the next exchange, and the next one, you could dial across the country for the price of a local call - however, he’s been known to trade in urban legends, so I wonder how true that is.
Interestingly, the solution implemented in UK phone boxes to prevent tap dialling was the installation of oil-damped receiver hook switches - so that they couldn’t be rapidly cycled. Seems a strange choice of solution - I suppose it must have been the easiest for retrofitting or something