Communications system
US7639950B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 17, 1996 |
| Grant date | Dec 29, 2009 |
| Priority date | — |
| Expiry date | Jul 17, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B10/1121
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A communications system incorporates a transmitter a receiver. The transmitter includes an infrared light emitting diode (LED). The LED output is positive or negative luminescence, i.e. above or below an equilibrium background intensity level respectively, according to the polarity of its bias signal. The receiver contains a lens to focus light from the LED onto a diode detector, from which signals pass to an amplifier, decoder and printer. Output signals from the LED have an average intensity equal to the equilibrium background intensity level and a frequency greater than 100 Hz or byte rate greater than 100 bytes/sec. They are not discernible by conventional thermal infrared imagers with frame rates of 50 Hz or less because integration in such an imager renders them indistinguishable from background.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.