帮忙用英语描述一下旧时的电视,不需太详细~

Television is a way of sending pictures through space by changing the light rays into electric waves which are picked up by a receiver that changes them back to light rays shown on a screen.
In its early stages of development,television employed a combination of optical,mechanical and electronic technologies to capture,transmit and display a visual image.By the late 1920s,however,those employing only optical and electronic technologies were being explored.All modern television systems rely on the latter,although the knowledge gained from the work on electromechanical systems was crucial in the development of fully electronic television.
The television consists of four principle sets of parts,including the exterior or housing,the audio reception and speaker system,the picture tube,and a complicated mass of electronics including cable and antennae input and output devices,a built-in antenna in most sets,a remote control receiver,computer chips,and access buttons.The remote control or "clicker" may be considered a fifth set of parts.
Television has become a major industry,especially in the industrialized nations,and a major medium of communication and source of home entertainment.Television is put to varied use in industry.