The photo shows the operator's console for AT&T's Voice Operation Demonstrator (Voder), featured at both the 1939 New AT & T VodermachineYork World's Fair and the Golden Gate Exposition. The console's keys were used to produce the different components of a human voice and the foot pedals controlled inflection. Apparently, it took considerable skill to make the Voder produce intelligible speech. By the Fair's second season, however, some operators had even learned how to make the Voder sing as well as talk. (On the Fair's last day, it sang Auld Lang Syne.) This photo appeared in the September 1939 issue of ETUDE MAGAZINE. I'm sending it along in case you want to include it along with the other photos on the AT&T page of the World's Fair Tour. (The above photo and text courtesy of Eric Beheim.)

Photo from:
www.stanford.edu/class/linguist238/lecture7.htm
(as of 12/6/10 page no longer available)

The Voder or Vocoder was invented by Homer Dudley.

In effect, Dudley had figured out how to synthesize sounds. And, thus, he quickly ascertained the vocoder (or voice coder) had creative potential beyond the transmission of phone calls.

To publicize his breakthrough, he created an offshoot called the Voder for the 1939 World's Fair in New York. Using a trained operator who manually pressed keys to produce sounds, the Voder (or voice operation demonstrator) could transmit complete intelligible sentences and imitate the sound of various farm animals.

Text and photo taken from Retrofuture.com Read more about Dudly and the Voder

Photo from Tales of the Future Past
http://davidszondy.com/future/
robot/voder.htm