Synchronous power communicating
First Claim
1. Synchronous power communicating apparatus for communication between a central station and remote stations over power lines that may also carry electrical power at power frequency comprising,a source of a carrier signal of frequency that is a harmonic of half said power frequency at said central and remote stations in the frequency range between 500 and 30 kHz for carrying digital data,a source of a digital data signal at said central and remote stations,means for establishing synchronism between each digital data signal and the electrical power frequency carried by said power lines,means for modulating a carrier signal with each digital data signal,means for coupling the modulated carrier signal to said power lines to transmit the modulated carrier signal over the power lines to a receiving means at each location including demodulating means for demodulating the modulated carrier signal to recover the digital data signal carried by the modulated carrier,means at each location coupling the modulated carrier signal from the power lines to said demodulating means,means for synchronizing the demodulating means with the electrical power carried by said power lines for demodulating the modulated carrier signal received at the receiving station to recover the digital data carried by the modulated carrier signal,the source of a digital data signal at said central location including means for providing a digital signal designating both a particular remote location to transmit a digital data signal to said central location and the data bit rate for transmission thereof that is a subharmonic of or the same as said power frequency,and means at each remote location responsive to reception of a digital control signal from said central location designating that remote location for transmission of a digital data signal to said central location for transmitting a digital data signal to said central location at the control designated data bit rate that is a subharmonic of or the same as said power frequency.
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Accused Products
Abstract
A remote meter-reading system interrogates meter stations over power lines and receives encoded meter readings over the power lines in synchronism with the power line frequency by superimposing a digitally modulated signal over the 60-Hz power frequency. The central control station transmits at a data rate of 60-baud and receives at a data rate that is 60-baud or a submultiple thereof, to reduce the demands on the remote meter station transceiver as compared to those on the central control unit transceiver. The bit clock at the central control unit and the meter stations is derived from the 60-Hz power line phase available at each station. Each meter station achieves message synchronization by continuously monitoring the data bit stream for a preset synchronization code and thereafter treats the following 21 data bits as address and function codes. Each meter station that is addressed responds at the data rate designated by the function code by transmitting with a message including the address and function bits for comparison at the central control station with that originally sent to facilitate error detection, and the meter reading encoded according to an error detecting code. A binary data bit is represented by quadrature phase lead and lag relative to reference phase of the character.
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Citations
21 Claims
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1. Synchronous power communicating apparatus for communication between a central station and remote stations over power lines that may also carry electrical power at power frequency comprising,
a source of a carrier signal of frequency that is a harmonic of half said power frequency at said central and remote stations in the frequency range between 500 and 30 kHz for carrying digital data, a source of a digital data signal at said central and remote stations, means for establishing synchronism between each digital data signal and the electrical power frequency carried by said power lines, means for modulating a carrier signal with each digital data signal, means for coupling the modulated carrier signal to said power lines to transmit the modulated carrier signal over the power lines to a receiving means at each location including demodulating means for demodulating the modulated carrier signal to recover the digital data signal carried by the modulated carrier, means at each location coupling the modulated carrier signal from the power lines to said demodulating means, means for synchronizing the demodulating means with the electrical power carried by said power lines for demodulating the modulated carrier signal received at the receiving station to recover the digital data carried by the modulated carrier signal, the source of a digital data signal at said central location including means for providing a digital signal designating both a particular remote location to transmit a digital data signal to said central location and the data bit rate for transmission thereof that is a subharmonic of or the same as said power frequency, and means at each remote location responsive to reception of a digital control signal from said central location designating that remote location for transmission of a digital data signal to said central location for transmitting a digital data signal to said central location at the control designated data bit rate that is a subharmonic of or the same as said power frequency.
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21. In apparatus for communicating from a central station to a plurality of remote stations over power lines that may also carry electrical power at power frequency, wherein the apparatus comprises transmitter means at the central station and receiver means at each remote station, the transmitter means and each receiver means being coupled to the power lines to transmit and receive signals thereover, respectively, wherein said transmitter means comprises a source of a carrier signal, a source of a digital data signal and modulation means for modulating said carrier signal with said digital data signal, and wherein each receiver means comprises demodulation means for demodulating the modulated carrier signal to recover the digital data signal carried by the modulated carrier signal,
the improvement wherein, said source of a carrier signal has a frequency that is a harmonic of one-half said power frequency and is within the range of 500 Hz to 30 kHz, the data bit rate of transmission is a subharmonic of, or the same as, said power frequency, the transmitter means further comprises means synchronizing the modulation means with the electrical power frequency carried by said power lines, and each receiver means further comprises means synchronizing the demodulation means with the electrical power frequency carried by said power lines.
Specification