AT the World's Fairs in New York and San Francisco great interest was shown in the speech synthesizer shown in the Bell System exhibits. In the December number of the Bell Laboratories Record, H. Dudley, of their research department, describes this device, known as the 'Vocoder'. The 'voder' is an offshoot of a more extensive system first demonstrated in its experimental stage several years ago. It first analysed spoken sounds and then used the information to control the synthesizing circuit. As World's Fair displays were then under consideration it was seen that the synthesizer, manually controlled, could be made into a dramatic demonstration. Development was at first concentrated in this field, but when a successful Voder became assured, attention was shifted back to the broader and parent system and it was called the 'vocoder', since it operates on the principle of deriving voice codes to re-create the speech which it analyses. The analyser is at the left and the synthesizer at the right of the vocoder.