Here's another use for the CDI: You are a speaker at convention and there's 500 people in the room. During or at the end of your speech you allow questions/comments from the audience. Instead of looking all over the room with bright lights overhead to locate someone with a question, you can have a CDI near you who will field the questions/comments for you. Not only does this make it easier for you, the speaker; other members of the audience is relieved from looking at the back of the one asking a question.