UnitDelay class public functions 
 
 Additional functions inherited from 
   Filter.
-   UnitDelay(void); 
 -  Sets internal sample values to zero.
 -   ~UnitDelay(); 
 -  Does nothing.
 -   void action(void); 
 -  Store the current incoming sample and update the output sample.
 -   sampleType output(int index); 
 -  Returns the one-unit delayed sample.