To set up Emergency System Override, hover over the Configuration icon from the Navigation bar, click on System setup and then select Emergency System Override. The emergency button is only visible to admin users.
You will then be able to choose the action that will be applied to all incoming calls when the emergency state is activated. Available options include playing a message and hanging up, redirecting to Voicemail or applying a TOD policy. You also have the option to disable broadcast queues while in emergency state.