An application can enable or disable text-to-speech output for a voice-text site. Disabling a site prevents the engine from playing text through the site. An application uses the IVTxtAttributes::EnabledSet member function to enable or disable a voice-text site and the IVTxtAttributes::EnabledGet member function to discover if the site is currently enabled or disabled.
The user can use the Speech control panel application to turn the system's speech capabilities on and off. When the system's speech capabilities are turned on or off, the WM_SPEECHSTARTED or WM_SPEECHENDED message is sent to all top-level windows in the system. An application can use these messages to determine when to enable or disable its voice-text capabilities.