Aid and devices Teaching 25 Design and construction 6 Educational technology 6 Compact discs in education 4 Interactive multimedia 4 Compact dics in education 2 Computer-assisted instruction 2 Electric motors 2 Electric power supplies and apparatus 2 Electronic appratus and appliances 2 Power electronics 2 Power supply 2 Study and teaching 2 Building, Brick 1 Dies (Metal-working) 1 Electric machinery 1 Electronic security systems 1 Foundations 1 Scaffolding 1 Transparencies in education 1 Visual education 1 Welding 1