中学生英语演讲稿2分钟作文 篇4

　　A TV picture starts with a TV camera. Some TV cameras are big and some aresmall. The cameras in TV studios are big. Camera operators roll the big camerasaround on wheels. There are usually several big cameras in a TV studio. Camerasused outside a TV studio are smaller. TV camera crews take the smaller camerasto news and sports events.

　　Some cameras send out live pictures to your TV set. Some cameras makevideotapes that get played later on a television program.

　　All TV cameras need electricity to work. A camera operator points thecamera at a scene. The camera picks up light from the scene. It changes thislight into an electric signal called the video signal. A microphone changes thesound of people talking or music playing into an electric signal called theaudio signal.