Importance

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Abstract

This invention is directed to various improvements in spread spectrum power line communications. One aspect of the invention relates to collision avoidance between varius 'slave' unit transmitters trying to send messages to a single 'master' unit receiver by detecting whether the transmission path is in use and refraining from transmitting if it is. Other aspects of the invention relate to controlling the frequencies of spread spectrum data messages transmitted, using gold codes to identify the slave units, and switching frequency bands on the powe line to avoid frequencies where there has been a deterioration of transmission. In each embodiment, the signal modulated over the power line is modulated by a signal which is synchronous with A.C. power flowing through the power line used for communications. The transmitted spread spectrum modulated signal then may be demodulated to isolate the transmitted data even when changes in the transmission characteristics of the power line (due to load changes and the like) occur.

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First Claim