whiteboard 70 x 40.1. Pressure sensing technology: The electronic whiteboard using the pressure sensing input method is equivalent to a touch screen of a computer. When the teacher touches the actual option on the screen with a finger or a pen, the computer automatically handles the equivalent operation. In fact, there are two laminated sensitive films inside the electronic whiteboard. When a certain point on the surface of the whiteboard is under pressure, the two films form a short circuit at this point. The controller of the electronic whiteboard detects the coordinate value of the pressed point and sends it through the interface. computer. 2. Laser technology: There is a laser emitter on each side of the electronic whiteboard using the laser tracking principle. After the electronic whiteboard is started, the laser emitter emits a laser to scan the surface of the electronic whiteboard. The special pen has the function of sensing the laser, so that when the teacher uses the stylus to operate on the electronic whiteboard, the laser emitter scans the position of the stylus. 3. Electromagnetic wave technology: The electromagnetic induction whiteboard adopts a pen that can emit electromagnetic waves, and the receiving coil film is arranged in the horizontal and vertical directions of the whiteboard. When the pen is close to the receiving coil film, the coil quotient senses the electromagnetic wave emitted by the pen. The closer the pen is to the pen, the higher the electric type that the coil film senses. 4. Infrared technology: The scanning grid of horizontal and vertical directions is formed by infrared receiving and transmitting tubes densely arranged around the display area to form a scanning plane network, when an object blocks a certain horizontal and vertical scanning line in the grid. The X, Y coordinates can be determined by the blocked infrared position in the horizontal and vertical directions. 5. Ultrasonic technology: Two ultrasonic receiving devices distributed at a fixed distance are placed on both sides of the screen. The pen used for positioning is an ultrasonic transmitter. When the pen moves on the surface of the screen, the emitted ultrasonic waves are received along the surface of the screen. The device detects that the distance between the pen and the two receivers can be converted by the time the ultrasonic wave is received.