Abstract: A position sensing device having an insulating board, a first conductive sensing element, a second conductive sensing element, an oscillator, conductive material, a differential amplifier, and a processor. The first and second spaced conductive sensing elements are on the insulating board. The oscillator generates an oscillating signals and the conductive material is spaced from the sensing elements. The conductive material receives the oscillating signal to create an electric field between the conductive material and the first and second sensing elements. The differential amplifier includes differential inputs that are connected to the conductive sensing elements. The signal levels at the differential inputs vary based on the position of a pointing object of a user relative to the first and second conductive sensing elements. The processor generates a position signal based on an output of the differential amplifier.

Abstract: A computer system comprises a keyboard (11), a display screen (13), a first pair of position-sensing electrodes (18.1, 18.2), a second pair of position-sensing electrodes (20.1, 20.2), a signal injection electrode (22), and an oscillator (27). The oscillator injects a signal via the signal injection electrode and the operator's left hand (L) into the operator's body, and this creates a field around the operator's right hand (R). The position-sensing electrodes are arranged underneath the keyboard and sense the strength of the field. This enables the position of the operator's right hand (R) in an X-Y plane above the keyboard to be determined. To this end the position-sensitive electrodes are connected via synchronous detectors (34, 44) and an analogue-to-digital converter (36) to a microprocessor (46), which operates to control the position of a cursor on the display screen.

Abstract: A computer system (10) includes a keyboard (11), a first pair of position-sensing electrodes (18.1 and 18.2), a second pair of position-sensing electrodes (20.1 and 20.2), a signal injection electrode (22) and an oscillator (27). The oscillator injects a signal via the electrode (22) and the operators left hand L, creating a field around the operator's right hand R. The position electrodes are arranged underneath the keyboard and sense the strenght of the field enabling the position of the operator's right hand R in an X-Y plane above the keyboard to be determined. Each position-sensing electrode is coupled to a difference amplifier (28 and 30) via a pair of buffer amplifiers (40.1, 40.2, 30.1, 30.2). The amplification factor of the buffer amplifiers can be varied so as to scale the field strength values sensed by the electrodes, thereby permitting the output of the difference amplifier to be varied so as to adjust the sensivity of the system to different positions of the operator's hand R.

Abstract: A computer system comprises a keyboard (11), a display screen (13), a first pair of position-sensing electrodes (18.1, 18.2), a second pair of position-sensing electrodes (20.1, 20.2), a signal injection electrode (22), and an oscillator (27). The oscillator injects a signal via the signal injection electrode and the operator's left hand (L) into the operator's body, and this creates a field around the operator's right hand (R). The position-sensing electrodes are arranged underneath the keyboard and sense the strength of the field. This enables the position of the operator's right hand (R) in an X-Y plane above the keyboard to be determined. To this end the position-sensitive electrodes are connected via synchronous detectors (34, 44) and an analogue-to-digital converter (36) to a microprocessor (46), which operates to control the position of a cursor on the display screen.

Abstract: A computer system comprises a keyboard (11), a display screen (13), a first pair of position-sensing electrodes (18.1, 18.2), a second pair of position-sensing electrodes (20.1, 20.2), a signal injection electrode (22), and an oscillator (27). The oscillator injects a signal via the signal injection electrode and the operator's left hand (L) into the operator's body, and this creates a field around the operator's right hand (R). The position-sensing electrodes are arranged underneath the keyboard and sense the strength of the field. This enables the position of the operator's right hand (R) in an X-Y plane above the keyboard to be determined. To this end the position-sensitive electrodes are connected via synchronous detectors (34, 44) and an analogue-to-digital converter (36) to a microprocessor (46), which operates to control the position of a cursor on the display screen.