Before
With Homer Dudley's Voder ("Voice Operation Demonstrator") it was possible for the first time to synthesize speech with an electrical device . The Voder still had to be operated manually. In order to master its operation, it took about a year of training. It was first presented in 1939 at the World's Fair in New York .
A wrist switch could be used to determine whether the original signal was generated by a sawtooth generator for voiced sounds (the frequency could be varied using a pedal) or a noise generator for unvoiced sounds.
This signal has now been changed with the help of several electrical filters controlled by the user to such an extent that whole sentences can be recognized.
The vocoder was developed parallel to the Voder , whereby the Vocoder, unlike the Voder, was not only designed as a demonstrator.