Video modem for transmitting video data over ordinary telephone wires
US5786844A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 30, 1996 |
| Grant date | Jul 28, 1998 |
| Priority date | — |
| Expiry date | Dec 30, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N11/02
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An apparatus and method is provided for modulating and transmitting full-motion, television-quality color video signals along with digital data signals over a pair of ordinary unshielded twisted pair telephone wires without interfering with normal telephone data on the wires. A transmission method is disclosed involving frequency modulation of a baseband video signal and subsequent filtering to suppress an upper sideband corresponding to a color component of the original video signal. The filtered signal is received from the telephone wires at a difference location, filtered, demodulated and provided to a display device. Full-duplex operation over the same pair of wires is possible, such that two video signals may be simultaneously transmitted, each signal having an approximate bandwidth of 6 MHZ and shifted to a desirable noninterfering frequency location within the approximately 20 MHZ of usable bandwidth on the telephone wires. No pre-emphasis or de-emphasis is required to achieve good quality video transmission. The system has many applications including video distribution, conferencing, and communications.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.