Are these special characters for displaying on a display or for signal, page names etc? If they're for the display then see the API spec. For DP610 it's on page 18 of 22. It tells how to show ASCII on screen.
see extract below:
Special characters can be inserted into the screen editor by using this character table. To create the desired character, type \ followed by the corresponding table coordinates.
Example: to create the degree symbol, type \260. The number 26 represents the row location of the character and 0 represents the column location of the character.
Richard