A graphics tablet or digitizing tablet allows the user to input graphics or drawings by hand, just as you would with pencil and paper. It also allows point-and found objects on the screen.
Passive tablets manufactured by Wacom, make use of electromagnetic induction, where the mesh of vertical and horizontal wires serve signal transmission and reception purposes. This change is made approximately every 20 microseconds. The digitizing device renders an electromagnetic signal which is received by the resonant circuit which is located in the pen.
When the tablet switches to receive mode, it reads the signal generated by the pen, this information, along with the coordinates found may include information on the pressure buttons on the pen or the angle in some tablets. (The pen includes a circuit inside that provides this information).
Using the electromagnetic signal, the tablet can locate the position of the stylus without touching the surface. The pen is not battery powered, but that energy is supplied by the grid of the tablet by resonant coupling. This technology is patented by the company Wacom.
Active tablets differ from the passive ones in that the stylus contains a battery or cell therein which generates and transmits the signal to the tablet. So are larger and heavier than the previous. Moreover, eliminating the need to feed the pen, the tablet can detect the signal constantly without having to switch between transmit and receive mode constantly, which means less jitter.
For both technologies, the tablet can use the received signal to ascertain the distance of the stylus to the tablet surface, the angle from the vertical in which is positioned the stylus and other information (for example: side buttons pencil, eraser).
Compared with touch screens, a digitizing tablet offers greater accuracy, the ability to follow an object that is not physically touching the tablet surface and can also learn more about the pen (angle, pressure). The digitizing tablets instead are more expensive and can only be used with the stylus or other accessories that work with a specific model digital tablet.