The primary function of DECtalk[R] Software is to convert ASCII text into synthesized speech output.  
The DECtalk synthesizer includes its own set of built in rules for text processing, as  well  as  a  large integral dictionary, and application specific dictionaries can be created by the developer or user.
In addition, a large number  of control and status functions are available. 
These functions are  used to  modify  the  speech parameters of DECtalk Software.   
Some of the functions include selecting the speaking voice,  rate, volume, tone generation, and pause lengths. 
