Retrotechtacular: The Voder from Bell Labs


This is the under-the-hood view of the keyboard for the Voder (Voice Operating Demonstrator), the first electronic device capable of generating continuous human speech. It accomplishes this feat through a series of keys that generate the syllables, plosives, and affricatives normally produced by the human larynx and shaped by the throat and tongue. This week’s film is a picture montage paired with the audio from the demonstration of the Voder at the 1939 World’s Fair.

The Voder was created by one [Homer Dudley] at Bell Laboratories. He did so in conjunction with the Vocoder, which analyzes human-generated speech for encrypted transfer and re-synthesizes it on the other end. [Dudley] spent over 40 years researching speech at Bell Laboratories. His development of both the Voder and the Vocoder were instrumental in the SIGSALY project which aimed to deliver encrypted voice communication to the theatres of WWII.

voder layoutIn this film, the Voder is first demonstrated with a flat, robotic rendition of the phrase “she saw me”. The operator then runs through the various possible inflections to show the flavor that the foot pedal provides. Inside the Voder is a group of band pass filters in parallel that span the frequency range of human speech. Excitations are received from either the noise generator or the relaxation oscillator, and selection between the two is made from the wrist bar. The pitch is controlled with the foot pedal. The band pass outputs are fed to ten gain pots under the operators fingers. Three additional keys manipulate the excitations to produce the consonant stop sounds like /t/, /d/, /p/, /b/, /k/, and /g/.

voder keyboardVoder’s pitch can be adjusted to emulate all kinds of voices, from man to woman to child. It is capable of speaking an any language the operator can speak. As a special bonus, Voder makes very convincing cow and pig sounds.

In creating the Voder, it was discovered that non-inflected vowels sounded like a foghorn, so vibrato was added to make them more human. This of course means that Voder can sing, and the operator gives a heartwarming performance of “Auld Lang Syne”.

For an operator, getting the Voder to speak is a difficult undertaking. Generating a single word requires the keying of several sounds in quick succession, along with simultaneous wrist bar action and pedal work to color the inflection. Bell Labs auditioned a few hundred girls to train in Voder operation, but ultimately had fewer than 30 expert operators. [Helen Harper], who you hear in this film, was considered the best. According to [Helen], mastery required about a year of constant practice.

[Thanks to Fran for the tip!]

[Voder keyboard image source]

30 thoughts on “Retrotechtacular: The Voder from Bell Labs

      1. My father, Stan Watkins, after perfecting the speech of Pedro, the Voder, also taught it to sing Daisy (I have a recording of that, alongside one of Hal the computer in 2001 Space Odessey singing Daisy as he dies. Arthur C Clarke said he got the idea from a friend at the Bell Labs.

    1. When Stan Watkins retired from the Labs in 1948, they offered him one of the Voders he had worked so hard to make talk. But as they would not pay for its transportation to England he declined. I’m glad to know there is still one on view.

      1. I’ve been working directly with Bell Labs to produce a modern replica of the VODER. It was just completed and delivered April 8, 2016. We have found two of the original ‘practice’ equipment racks for the VODER, but our team would love to hear from anyone with information about the location of any of the operator consoles (with the keyboards). They have been lost from the AT&T archives.

        1. Kudos for doing this. I have lots of information from my Dad’s work on the original 1936-39 Voder but nothing about the consoles except photos whichI think have already been posted online.
          I’d love to know your company (or is this an independent project?) and what you propose doing with the Voder. Do keep in touch.

  1. Current cell phones only transmit 2 octaves (4to1) range, the high pitches of diction. The hum-tone of the voice is encoded this old fashioned way! That’s why people sound so fake on a cell phone. Imagine with it fixed pitch. Robot voice on every call.
    Coming soon: 5 octave cell phones. They will finally sound about as good as an old fashioned landline.

    1. Weird. People sound exactly the same on the cell phone as they do in person on my phone. Are you still carrying around a startac or something? Or maybe you just have a bunch of robots calling you?

      1. My old StarTAC sounded pretty darn good, with a dynamic range similar (to my ears) to that of a landline phone. It is actually my favorite cell phone of all the ones I’ve used over the years.

        1. Well, maybe someone pranked echodelta’s phone and made it so that it calls chatbots instead of the people they think they are calling.

          Point is: wtf? I forgot after thinking up that brilliant idea for a prank!

          1. Analog mobile voice signals at one time carried nearly full fidelity voice signals. This is part of the reason analog used so much power. The power needs and the throughput are two reasons the analog signals gave way to digital. Our ‘modern’ mobile phones sound horrible compared with the first mobile phones, which were analog.

  2. We dodged a bullet with the Voder. At its debut there was other new technology demonstrated at the same fair that combined with the Voder and tape recordings could have made voice activated voice mail and robo-calling with synthesized voice possible.

    Just imagine Ma Bell with huge banks of tape recorders to store messages and Voder voices on tape saying things like “You have. Zero. New messages.” “To delete. Message. Say Seven.”

    Thankfully, that mashup wasn’t conceived until well into the solid state digital electronics era!

  3. My father, Stan Watkins, Bell Labs engineer, taught the Voder to talk in work 1936, and then taught 28 telephonists to play it for the Worlds Fair in NY and the Golden Gate Exposition in 1939. And he also taught the Voder to sing Daisy. I have the record. Look at my blog which will be featuring my father’s work (when I stop doing the NoBloPoMo blog-a-day). My site is

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