Tablet with system power saving features including reactivation by pen contact after inactive period
US5568409A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 14, 1994 |
| Grant date | Oct 22, 1996 |
| Priority date | — |
| Expiry date | Dec 14, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F3/0488
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A tablet system has an improved operation for saving power. During a digitizing period, the tablet supplies power to resistive sheets that produce analog pen position signals and to the sample and hold circuit and the analog to digital converter that operate on these signals. During a wait state, power is removed from these components and a separate circuit detects contact with the tablet surface by a pen. A pen activity circuit that uses less power is also disclosed. The pen activity detecting circuit has a resistor in circuit with the two resistive sheets. This resistor and associated circuits are independent of the normal path for signals that denote pen position and thereby allow these components to be turned off. When the pen is positioned on the tablet surface, the two resistive sheets are brought into contact in the normal way for detecting the pen position. During a period of pen inactivity, this contact produces a current in the resistor. The associated voltage is detected and power is applied to the resistive sheets and to the sample and hold circuit and analog to digital converter for normal operation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.