systems designed for everything from the casual user to multinational organizations. It is now common for laptop manufacturers to include multi-touch touchpads on their laptops, and tablet computers respond to touch input rather than traditional stylus input and it is supported by many recent operating systems. A few companies are focusing on large-scale surface computing rather than personal electronics, either large multi-touch tables or wall surfaces. These systems are generally used by government organizations, museums, and companies as a means of information or exhibit display. Large scale multi-touch surfaces are manufactured by Finnish company MultiTaction on their 55" MT Cells (55" screens) who also have office locations in London, California and Singapore. MultiTaction also build unique collaboration software especially designed for multi-touch screens such as MT Canvus and MT Showcase. Implementations Multi-touch has been implemented in several different ways, depending on the size and type of interface. The most popular form are mobile devices, tablets, touchtables and walls. Both touchtables and touch walls project an image through acrylic or glass, and then back-light the image with LEDs. Touch surfaces can also be made pressure-sensitive by the addition of a pressure-sensitive coating that flexes differently depending on how firmly it is pressed, altering the reflection. Handheld technologies use a panel that carries an electrical charge. When a finger touches the screen, the touch disrupts the panel's electrical field. The disruption is registered as a computer event (gesture) and may be sent to the software, which may then initiate a response to the gesture event. In the past few years, several companies have released products that use multi-touch. In an attempt to make the expensive technology more accessible, hobbyists have also published methods of constructing DIY touchscreens. Capacitive Capacitive technologies include: Surface Capacitive Technology or Near Field Imaging (NFI) Projected Capacitive Touch (PCT) Mutual capacitance Self-capacitance In-cell Capacitive Resistive Resistive technologies include: Analog Resistive Digital Resistive or In-Cell Resistive Optical Optical touch technology is based on image sensor technology. It functions when a finger or an object touches the surface, causing the light to scatter, the reflection of which is caught with sensors or cameras that send the data to software that dictates response to the touch, depending on the type of reflection measured. Optical technologies include: Optical Imaging or Infrared technology Rear Diffused Illumination (DI) Infrared Grid Technology (opto-matrix) or Digital Waveguide Touch (DWT) or Infrared Optical Waveguide Frustrated Total Internal