Teaching functions for which television, radio, and audiocassettes are particularly appropriate are considered, based on the use of broadcasting at the Open University. Television is useful for the following purposes: to demonstrate experiments or experimental situations; to illustrate principles involving dynamic change or movement; to illustrate abstract principles through the use of physical models; to illustrate principles involving more than one dimension of space; to demonstrate the visual picture of an area or building; to provide primary resource material or case-study material; to demonstrate decision-making processes; to change student attitudes; to study films or dramatic performances; and to teach sketching, drawing, or painting techniques. Audiocassettes are more appropriate than radio to analyze detailed visual material, to review complex arguments, and to witness naturally occurring events. Radio is more appropriate than audiocassettes to provide remedial tutorials; to relate course material to current events; to provide criticism or alternative viewpoints to course material; and in other cases when only hearing the material would be sufficient. (SW)