Unity uses Call Handlers to precess and forward call based on input from users. Call handlers consist of a specific set of instructions or actions that enable Unity to answer calls, plau a greeting, prompt callers, take messages, provide recorded information, and transfer calls.
There are several default Call Handlers in Unity (which are undeletable) including:
- Opening Greeting
- Operator Greeting
- Goodbye
Also Interviews Handlers and Public Distribution are some other Call Handler form.