Electronic blackboard and accessories such as writing tools
USRE35329E · kind E · reissue
Assignee
Inventors
Key dates
| Filing date | Jun 10, 1993 |
| Grant date | Sep 17, 1996 |
| Priority date | — |
| Expiry date | Jun 10, 2013 |
Classification
- Technology area (CPC —)General
Abstract
A characteristic and the position of an implement with a tuned circuit having one of plural resonant frequencies are determined. AC energy at the plural different resonant frequencies is supplied to a two-coordinate direction coil arrangement of a position sensing tablet. The tuned circuit changes the current flowing in the coil arrangement at the implement resonant frequency. The current change is used to signal the implement position and characteristic. The implement may be an eraser for supplying a signal to an electronic display and for removing a mark from a surface of a visual display overlaying the tablet of the eraser. A housing includes a surface for erasing the marking and two tuned circuits each having a reactance positioned close to opposite edges of the erasing surface. Two switches, when activated, cause the tuned circuits to have different resonant frequencies. The switches are respectively activated when opposite eraser edges are being pushed against the display surface. The implement may also be one of a plurality of markers, each for a different color. Another display responds to the signals to display the position and colors of the markings and selectively remove…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.