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BELL SYSTEM TECHNICAL JOURNAL 



Fig. 6 — Block diagram of the voice mechanism. 



breath tone for unvoiced and the vocal cord tone for voiced sounds. 

 For simpHcity the carrier selection is shown after instead of before the 

 carrier generation. These carriers are modulated by the message wave 

 to produce the output of speech in the form of the message-modulated 

 carrier in the audible range of frequencies. 



Figures 7 and 8 show similar block schematics for the vocoder and 

 the voder. The voder circuit has been simplified by the omission of a 

 few controls for easier operation. In these electrical synthesizers, the 

 carrier is provided by a buzzer-like tone from a relaxation oscillator for 

 the voiced sounds and from a hiss-like sound from a gas-filled tube for 



IDEA 



(DETAILS ARE AS 



IN COMPLETE CIRCUIT 



SHOWN IN FIG.2) 



MODULATORS | RADIATOR | SPEECH 



\ \ \ I I 

 ,' ' I I I 



Fig. 7 — Schematic circuit of the vocoder. 



