To use the text-to-speech program output functionality, you need the Festival text to speech engine as described in the
Text-To-Speech setup page.
Script boxes and command shell selections run programs on the VOCP host, on behalf of the caller. After the program has executed, a response is played for the caller - the exact type of response is selected by the VOCP system administrator.
If you set the box's return value to tts and the program outputs 1 or more lines of ascii text on standard out, that output will be converted to sound using Festival and read to the caller.
This way, you could have a box that fetches a page through the web, to read the weather or the latest slashdot news, you could have the system read newsgroup messages or anything else.
Please see the box configuration and box types pages for more details.