Audiovisual devices are used in almost all schools in the world.; these may include pictures, posters, charts, models, mock-ups, slides, filmstrips, and motion pictures. Records and tape recorders are used extensively in the teaching of languages. Motion pictures on various subjects are part of classroom instruction.Closed-circuit television instruction is growing rapidly, enabling a teacher to instruct students in many classrooms. By means of videotape, a single lesson can be presented many times.
The instruction provided by teaching machines is specialized and often programmed to serve the student's individual rate of progress, thus permitting interaction between the student and the machine. Teaching machines, however, have not made as significant a contribution to education as was first expected. Advances in computer technology are likely to have a wide and growing impact on education.

Reference

"Communication," Microsoft(R) Encarta(R) 96 Encyclopedia. (c) 1993-1995 Microsoft Corporation. All rights reserved. (c) Funk & Wagnalls Corporation. All rights reserved.