Interacive electronic whitebord is man-machine conversation high -tech productions for edauction and conferences. It can be compatible with projectors, computers and other tools to achieve dust-free writing, free writing, remote comunication functions, from the hardware point of view, the Interactive Whiteboard integrate with large-screen projection technology, precision positioning and testing technology. At this stage, in the international or the domestic market, there are many technicals to achive Whiteboard' precise positioning , which the Representative is Electromagnetic sensors, infrared, resistance, ultrasound , CCD technologies and so on . Each technology has different characteristics and advantages, and obtian a certain market share in Whiteboard market.
Here mainly introduce from the realization of a technical perspective on the current of the three most commonly used precise positioning technology Whiteboard testing technology brief introduction. Here mainly brief introducefrom the technical perspective on the current of the three most commonly used test Whiteboard precise positioning technology brief introduction.
1: Resistance membrane technology
Resistance membrane technology's principles are: Whiteboard basic structure is consist of multimembranes ,which include horizon film resistor, insulation grid , Conductive Films , Vertical membrane resistance and so on . And compisition membranes have the same size as the using regional.the working principle is adding a fixed voltage to the Resistance membrane . In the absence of external force, the conductive films don't contact the Resistance Films and no voltage was measured, so there will be no reaction positioning informations. When press with a hard object at a certain point of the resistance films, the Current through the conductive film was reading by test circuit . As from the midpoint of a potentiometer test an unstable voltage . the voltaget has no businesss with the location of the touch poinst, According to the voltage, which get from the horizontal and vertical directions, can be converted to the touch points's X and Y directions position . Resistive touch screen is a grid Scanning mode, the feature is that it can reflect the location of pressure object punctured the membrane surface, it can reflect the pressured location of objects ,When some objects press on the surface of membranes.

Technology Advantages and Disadvantages :
Advantages：
1 、 Relatively accurate positioning.
2 、 Writting without special pens, can do touch operation .
Disadvantages：
1 、Difficult to write, not enough efforts can not show up handwriting.
2 、 Afraid to scratch, once scratched, it can not be used.
3 、 Slowness response.
4 、 Cann't make large size whiteboard.
Because of technics reasons, few companies can be mass producted this boards. At present this products' market share was rapid decline and local manufacturers less use of this technology.
2：Electromagnetic Induction

Electromagnetic Induction's working principles are : Electromagnetic waves can be spread through air and Insulation objects , Electromagnetic induction is using an electromagnetic pen to launched Electromagnetic waves ,which are consist of the receiving coil films of the level and the vertical directions,And membranes have the same size as the using regional。 Positioning theory is that the electromagnetic pens launched the electromagnetic waves by intermittent way. T electromagnetic launch, when T receiver coil around the membrane, the induction coil to the T will launch the electromagnetic . When electromagnetic pens close to the membrane around the receive coil, the coil line will induct the electromagnetic waves which launched by the electromagnetic pen. T recently from the induction coil to the EMF group higher, in accordance with the horizontal direction and the vertical direction to the electromotive force induced by T can be calculated where the X, Y coordinates position.
Technology Advantages and Disadvantages

Advantages：
1 、 Relatively accurate positioning.
2 、 Pressure in the process of writing,which the level of writing is different,the handwriting thickness is different.
3 、Display area 's evenness is good .

Disadvantages：
1 、 Do not touch , must use spencial pens to write. Inconvenient for teaching management.
2 、Slowness response, that is, handwriting just show after writing.
3 、Afraid of scratches, Once scratches in the middle of the plate ,which may not be used.
4 、Difficult to produce large size whiteboard.
5、 Products are easily interfere by power equipment, electronic equipment and other metal things.

This is a common technical for early Whiteboard , at present the market share is relative stable.
3、Infrared sensor technology

    Infrared technology 's principle is : clouds in the display surrounded infrared receiver and the launch of a horizontal and vertical grid scanning direction, forming a planar scanning network, when the infrared light can be blocked to stop objects in a grid Infrared on the horizontal and vertical scan lines, it could be blocked by the horizontal and vertical position of determining the direction of infra-red X, Y coordinates to achieve the positioning coordinate.
Advantages and Disadvantages
Advantages：
1 Positioning accuracy 、 High precision.
2 、No need special pens to write, can use fingers , ferule or other opaque objects to write or to operate , such as a pointer to write or touch operation.
3 、Not afraid of scratches , even if boards have any scratches, which don't affect to use the boards.
4 、Long lifetime.
5 、Speediness response .

Disadvantages：
1 、No pressure flu response （Software can be offset ）.
2 、Early technology may be affected by the strong infrared light, at present which have been improved.
According to International authoritative market survey agencies ' analysis report, infrared Interactive electronic Whiteboard products accounted for 9% of the world's market share in 2005, 17.4% in 2006, which grow rapidly and More and more accepted by users, and are espacilly popular in education area.

    A large screen product which are used in a daily 8:00 programe of CCTV " morning news of the world" is adopting the infared technology.
Generally speaking,because the infrared sensor technology is rather stability and operation is convenient, which is the trend of developing of Interactive Whiteboard in near future.