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A communication system for carrying out communication between a plurality of stations through an electric power line operating in a commercial power frequency band. Spread spectrum modulation of an information signal, employing a pseudorandom code sequence is used at a transmitting station. Spread s

A communication system for carrying out communication between a plurality of stations through an electric power line operating in a commercial power frequency band. Spread spectrum modulation of an information signal, employing a pseudorandom code sequence is used at a transmitting station. Spread spectrum demodulation is carried out in a receiving station to reproduce the information signal. The modulated signal is spread over a wide frequency band different from the commercial frequency band. Each station may comprise both of a transmitter and a receiver, and may be specified by a an assigned destination address that also is transmitted. The destination station address may be indicated either by an address signal or by an additional pseudorandom code sequence peculiar to a destination station. Alternatively, polling operation is carried out through the electric power line by a polling station to select one of the stations. Preferably, another pseudorandom code sequence is superposed on the modulated signal so as to specify a synchronization signal and different from the pseudorandom code sequences conveying the information signal and/or the destination address.

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A system for use in conveying a tranmission signal from a transmission station to a reception station through an electric power line for electric power of a commercial frequency falling within a first frequency range, said electric power line having a variable loss, said transmission station compris

A system for use in conveying a tranmission signal from a transmission station to a reception station through an electric power line for electric power of a commercial frequency falling within a first frequency range, said electric power line having a variable loss, said transmission station comprising: modulation means responsive to said transmission signal for carrying out spread spectrum modulation of said transmission signal by the use of a first pseudorandom code to produce a modulated signal which is subject to said spread spectrum modulation and which is dispersed in a second frequency range different from said first frequency range; sychronization signal producing means for producing a sychronization signal; and combining means coupled to said electric power line, said modulating means, and said synchronization signal producing means for combining said modulated signal and said synchronization signal into a combined signal to supply said electric power line with said combined signal; said reception station comprising: demodulating means coupled to said electric power line for demodulating said combined signal into a demodulated signal by the use of a second pseudorandom code corresponding to said first pseudorandom code, said demodulated signal comprising a reproduction of said modulated signal and a synchronization component representing said synchronization signal, and having a variable level resulting from said variable loss of the electric power line; clock pulse generating means coupled to said demodulating means for generating a sequence of clock pulses in response to said synchronization component and said variable power level; and means coupled to said clock pulse generating means and said demodulating means for supplying said demodulating means with said second pseudorandom code which is synchronized with said clock pulse sequence.