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 (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.