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1948 pushbutton dialing field trial set found!

Started by paul-f, July 06, 2012, 03:45:14 PM

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Thanks to John LaRue and Wayne Merit of the JKL Museum, I had the opportunity to study and photograph a set that was on its way from Connecticut to the Museum.  This provided an outstanding opportunity to expand on the insights derived from brief glimpses of similar sets in the past.

This is one amazing telephone!

The closer we look, the more interesting it becomes.

For your holiday viewing pleasure, I've posted some preliminary results, including more details on the mechanical linkage and sound samples of the tones here:

Visit:         WE  500  Design_Line



Interesting, but - just so wrong trying to generate tones completely mechanically.


That's pretty cool, and hearing the sound clips of the phone dialling sounds pretty unusual compared to the electronically-generated tones we're used to in this day and age!!! :D

I read somewhere that the reeds needed frequent re-tuning, as they apparently fluctuated with stress, temperature and other issues that mess with the metal, though I can't recall where I read that... ???

And I can't help but notice the number dialled, 555-1212, that was used in Grand Theft Auto 3 as the number for "Fernando's New Beginnings", and read out as "Cinco cinco cinco, one y dos, and one y dos" (as in, One of those, I guess!!), you'd have to play the game and listen to the "Chatterbox" in-game radio station to understand why it's funny... :D

Russ Kirk

I remember when this or a similar set sold on eBay a couple years back.  It sold for $17,899.99.    I saw a different set highlighted in the TCI newsletter December 2008. I'm sure there were a few more made.  

Does anyone know of how many are still in existence today?        
- Russ Kirk


Kinda sounds like pounding on the tenement house water pipes.

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson


Quote from: Russ Kirk on July 06, 2012, 06:11:41 PM
I remember when this or a similar set sold on eBay a couple years back.  It sold for $17,899.99.    I saw a different set highlighted in the TCI newsletter December 2008. I'm sure there were a few more made.  

Does anyone know of how many are still in existence today?        

The Singing Wires article in December 2008 was about the ebay sale and included info from both the seller and buyer.  Photos of that set on my site are captioned "AW photo."

I doubt that anyone knows how many are out there.  I only know the location of four of them.  Three are pictured on my site and the fourth is in the AT&T Archives.

Does anyone know of others?
Visit:         WE  500  Design_Line



Very cool!  I too remember that phone that sold for nearly 18k a couple years ago, that's the highest I've ever seen for one of our old time phones.  Interesting how long and hard they were trying to find some sort of tonal push button dial system. 


There was another one in the pioneer museum in the BellSouth building in Atlanta. That museum is now closed.
"C'est pas une restauration, c'est une rénovation."--François Martin.


WOW!!! Christmas has come early!!!   ;D

I found the article that was mentioned here.  That comment from the "source at Lucent" gave me chills though!   :o

This is fantastic, I had wondered for a long time what the tones would sound like, this has really made my day! Thanks Paul for posting.

Now if we could just hear some of the other field trial sets. I love how you can hear what they're trying so hard to do in spite of not yet having the right tools. Brilliant!

You can also hear MF tones here at 5:18. Does anyone know how these were generated?

I think I read that some of the other later Touch Tone prototypes also used MF tones.


Hmmm, I just thought of something. Did anyone ever try to phreak with one of these? Somehow it's funnier this way.  ;D

Someone should ask Captain Crunch!



Steph analyzed the audio file and identified the tones produced by the set.  See his great charts and some added background info on the updated page...

I also looked for additional sound files for comparison and found similar clips in the Bell System movies:

  Speeding Speech - 1950 (at about 5:20 as indicated above)
  Dialing the Nation - 1955 (at about 7:00)

Both can be found on the AT&T site or

Visit:         WE  500  Design_Line



Wow, that's amazing, such fast moving times we live in, being able to see the waveforms in so much detail; I remember reading that part of the reason in band signalling wasn't immediately recognized as a weak link is that the MF signal recognition equipment was so expensive; little did Ma Bell realize that this wouldn't be the case for much longer, thanks in large part to her inventions!

On a related note, I was browsing weather phone recordings and came across this charming recording.  ;)

The first time I heard MF tones was in Speeding Speech and they sounded so beautiful to me in a strange, hauntingly familiar sort of way.

One of these days I'd like to have a blue box with a 16 key keypad for the standard 12 DTMF keys as well as the ABCD tones, with a switch to change to MF mode, to play the tones for 0-9, 11/ST3,  12/ST2,  KP/ST2, KP, ST and of course the 2600 Hz tone.  :)


Anyone want to hear more MF tones?  ;D

You can also read more about phone phreaking here, and it's possible to play the tones on your PC!