Magnetic bead-blackboard is a kind of magnet-reverse disploy in response to magnetic pen or eraser to force the two-colored magnetic beads to turn backward and forward. Magnetic nail-blackboard has the simple structure of permanent-magnet nails which are short rods and can be attracted out and pushed into the porous board. Magneto-optic blackboard and electron-optic blackboard use separately the magnetic semiconductor and flip-flop circuit to trigger their luminous displays. Electrophoretic blackboard, electric discolored blackboard and liquid crystal blackboard use separately their relevant display-techniques. For light-sensitive blackboards there are several light-sensitive materials can be selected at disposal. Televison blackboard that can be written either by television scanning or by handwriting with electric pen is an ideal tool for electric audio-visual aids of education. |