Digital communication system for remote instruments
First Claim
1. In a communication system for communicating data from a remote station to a central station, in combination,(a) a power distribution line for supplying d-c operating power from the central station to the remote station,(b) a first voltage regulator at the central station for applying a regulated d-c voltage to the power distribution line,(c) a second voltage regulator at the remote station for providing a regulated d-c station operating voltage from the voltage and current applied thereto over the power distribution line, said second voltage regulator being of the type which draws an approximately constant d-c operating current,(d) transmitting means connected to the output of the second voltage regulator to modulate the current flowing in the power distribution line in accordance with a digital signal to be transmitted to the central station, said transmitting means having a first state in which it draws a first predetermined current from said output and a second state in which it draws approximately no current from said output,(e) signal receiving means at the central station for producing a digital signal that varies in accordance with the modulated current in the power distribution line,(f) whereby the operating voltage of the remote station remains approximately constant during the operation of the transmitting means.
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Accused Products
Abstract
A communication system for communicating digitally encoded information from a remote transmitting station to a central receiving station. The central station supplies d-c operating power to a remote station through a d-c power distribution line. A voltage regulator at the remote station receives the d-c operating power and derives therefrom a constant d-c voltage for powering the circuitry of the remote station. A digital transmitter at the remote station changes the magnitude of the current drawn through the voltage regulator, in accordance with a message to be transmitted, and thereby changes the current in the power distribution line without affecting the voltage supplied to the circuitry of the remote station. These line current changes are detected and decoded at the central station to reconstruct the transmitted message.
76 Citations
18 Claims
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1. In a communication system for communicating data from a remote station to a central station, in combination,
(a) a power distribution line for supplying d-c operating power from the central station to the remote station, (b) a first voltage regulator at the central station for applying a regulated d-c voltage to the power distribution line, (c) a second voltage regulator at the remote station for providing a regulated d-c station operating voltage from the voltage and current applied thereto over the power distribution line, said second voltage regulator being of the type which draws an approximately constant d-c operating current, (d) transmitting means connected to the output of the second voltage regulator to modulate the current flowing in the power distribution line in accordance with a digital signal to be transmitted to the central station, said transmitting means having a first state in which it draws a first predetermined current from said output and a second state in which it draws approximately no current from said output, (e) signal receiving means at the central station for producing a digital signal that varies in accordance with the modulated current in the power distribution line, (f) whereby the operating voltage of the remote station remains approximately constant during the operation of the transmitting means.
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8. In a communication system for communicating information from a remote station to a central station, in combination,
(a) a plurality of power distribution conductors for supplying d-c operating power from the central station to the remote station, (b) first voltage regulating means at the central station for regulating the voltage applied to the power distribution conductors, (c) second voltage regulating means at the remote station for producing a regulated d-c station operating voltage from the voltage received over the power distribution conductors, said second regulating means being of the type which draws an approximately constant d-c operating current, (d) signal transmitting means connected across the output of the second voltage regulating means for drawing a first predetermined current from said output when a digital signal is being transmitted from the remote station to the central station and for drawing a second predetermined current from said output when no digital signal is being trnsmitted from the remote station to the central station, (e) signal receiving means at the central station for sensing the flow of said first and second predetermined currents and for reconstructing said digital signal therefrom, (f) the difference between said first and second currents being sufficiently small that the operating voltage of the remote station remains approximately constant before, during and after signal transmission from the remote station.
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18. In a communication system for communicating information from a remote station to a central station, in combination,
(a) a plurality of power distribution conductors for supplying d-c operating voltage and current from the central station to the remote station, (b) voltage regulating means at the remote station for producing a continuous regulated d-c station operating voltage from the voltage and current received over the power distribution conductors, said voltage regulating means being of the type which draws an approximately constant operating current, (c) digital signal generating means at the remote station for generating a digital signal for transmission to the remote station, said generating means being of the type that draws an approximately constant operating current, (d) switching means for switching the current in the power distribution conductors between first and second predetermined values in accordance with said digital signal, said switching means having a control circuit connected to receive said digital signal and a power circuit connected to the output of the voltage regulating means, and (e) signal receiving means at the central station for sensing the flow of said first and second currents and for reconstructing the digital signal therefrom.
Specification