An electromagnetic pen digitizer is integrated into a flat panel display assembly using "bent TAB" active electronics. Integration is performed by placing a discrete electromagnetic pen digitizer further inside the flat panel display assembly itself behind the diffuser backlight component, but in front of the "bent TAB" active electronics. Interference from the active electronics is avoided because they are not in between the digitizer and the pen operating upon the flat panel display. The electromagnetic pen digitizer is integrated into the flat panel display assembly by inserting the digitizer into the flat panel display assembly behind the diffuser backlight during the routine manufacture of the flat panel display assembly. Alternatively, the discrete electromagnetic pen digitizer is bonded to the diffuser backlight earlier in the manufacturing process; the combined diffuser backlight/digitizer component is placed into the flat panel display assembly during the routine manufacture of the complete flat panel display assembly. By integrating such a digitizer into the routine manufacturing process of a flat panel display, a standard "off-the-shelf" flat panel display may be used. The digitizer may be directly coated onto the diffuser backlight through an indium tin oxide (ITO) coating on the backlight itself. Also, an electromagnetic digitizer may be fabricated onto the front of the diffuser backlight by using a thin-film etched flexible circuit technique or a silk screen printed thin-film technique. Integrating an electromagnetic pen digitizer in this fashion allows for greater use of "off-the-shelf" display panels with only slight modifications.

A method and apparatus is provided for defining expanded touch zones for active control keys on a touch sensitive user interface panel. The user interface panel has one or more active control key display areas that each display a respective active control key, each active control key indicating an active control function that is available for selection by a user. The user selects a desired active control function by touching a probe to the user interface panel in a location corresponding to a touch zone defined for the active control key that indicates the desired active control function. Expanded touch zones for each active control key are defined, the expanded touch zone for each active control key having an area that is larger than the corresponding display area for the control key. When the user touches the probe to the interface panel, a determination is made as to whether the probe has touched an expanded touch zone for any active control key and if it has, the active control function indicated by the active control key corresponding to the expanded touch zone touched by the probe is selected, and if it has not, an indication is provided that no active control function has been selected. The size of the expanded touch zone defined for each active control key varies depending upon the existence and location of other active control keys on the display panel.

A pressure sensitive pointing device or pen is described for use with an electronic tablet that determines the position of the pointing device on the surface of the tablet. The pointing device incorporates a variable reluctance circuit responsive to the force exerted on the pen point for modulating a radiating frequency, emanating from the pen, in proportion to the force.

Disclosed is electromagnetic transducer (10) that does not require complex analog to digital, digital to analog converters, microprocessors or large memory circuitry. The transducer has a helical tablet coil (22) with tap nodes (24) spaced between its end extremities (26). In one configuration, an oscillator (42) drives the tablet coil for simultaneously producing oppositely directed currents on opposite sides of selected taps, creating a moving fringing field (34) that is compatible with modern graphic display tablet technology. A control circuit (40) of the transducer has a closed-loop integrator (82, 106) for detecting the centroid of a received stylus signal (AC) from a stylus coil (36). Analog and digital versions of the integrator are disclosed. In another configuration, the oscillator (174, 175, 176, 177) drives the stylus coil (162) for variably coupling magnetic flux to the tablet coil, a receiver signal (190) that is coupled from the end extremities being responsive to the position of the stylus coil and the taps selected. A preferred configuration of the tablet coil has separate oppositely wound coil components ( 22a, 22b).

A portable electronic signature system includes a base unit and a wireless remote unit that incorporates graphic tablet digitizer for signaling to a PC of the base unit signature data of a stylus being moved to produce a handwritten signature. The base unit transmits trigger signals for recognition by the remote unit, which also transmits identification signals to the base unit, respective alarms being activated in both the base and remote units in the event that recognition of the identification signals is interrupted by the remote unit being transported out of range. Also disclosed are a method for using the system, a cannister having a wireless alarm for use in a mechanical transport system, and the cannister in combination with a base unit.