Two Way Tv Via The Phone Lines
TELECOMMUNICATIONS companies have been searching for years for a means of delivering two-way, broadcast-quality video to desktops and TV sets without having to install expensive new cabling systems. Several schemes under development would transmit interactive TV over the standard copper wires that run into most homes and offices, but the broadcasts are often of inferior quality.
Objective Communications Inc. in Chantilly, Va., thinks it has a better way. It has patented a signal-processing technology, VidModem, that can provide simultaneous two-way video, data, and voice transmissions to a personal computer over the same copper wires already in place for phone calls. Targeted for businesses, the technology can be routed through the office switchboard.
The trick: VidModem transmits via an FM signal rather than the AM signals used to distribute most TV programming through cable or over the airwaves. FM is not as susceptible as AM to interference and distortion but needs 24 megahertz of bandwidth, while copper wires can only carry 20 Mhz. VidModem compresses the FM signal using a modulation system similar to that used in AM broadcasts. Objective Communications President Steven A. Rogers says the company expects to start shipping a commercial system by yearend.
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