System and method for providing back-lighting to a keypad
US6977648B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 29, 1998 |
| Grant date | Dec 20, 2005 |
| Priority date | — |
| Expiry date | Oct 29, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/23
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A system for providing a first signal to a flip circuit and receiving a second signal from the flip circuit over an electrical path adapted for use with a keypad having a keypad lighting circuit. The system includes a first circuit for providing the first signal to the flip circuit via a first electrical path, the first signal having alternating first and second states. A second circuit generates a second signal. A third circuit receives the second signal via the first electrical path. The second signal is received during the second state of the first signal. In a more specific embodiment, the first and second states are continuously alternating states. The first signal provides power to the flip circuit when the first signal is in the first state. The first circuit further includes a signal generator for adjusting a duty cycle of the first signal. The signal generator includes a voltage source, a switching circuit connected to the voltage source, and a control circuit connected to the switching circuit. The control circuit causes the switching circuit to output the first signal having first and second states at the duty cycle. The switching circuit includes a transistor having a c…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.