Systems for transmitting information in an alternating current electricity supply system
First Claim
1. In a system for transmitting information in an A.C. electricity supply system by reducing the instantaneous value of the A.C. supply voltage during the same small fractional part of each of a selection of cycles of the supply voltage waveform, said part including a time of voltage zero, a transmitter comprising:
- controllable switch means connected across said supply system in an effective zero impedance path so as to effectively shortcircuit said supply system throughout the whole of any period that the switch means is closed and thereby draw from said system throughout the whole of any period that said switch means is closed a current of sufficient magnitude to reduce the instantaneous value of the A.C. supply voltage during the time that said switch means is closed and conducting; and
switch control means for closing said switch means for a said small fractional part of any selected single cycle of the supply voltage waveform.
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Reexamination
Accused Products
Abstract
A system for transmitting information in an alternating current supply system wherein information is transmitted by reducing the instantaneous value of the supply voltage during a corresponding period in each of a selection of cycles of the supply voltage, the selection of cycles determining the information transmitted. To minimize disturbance of the system voltage the period of alteration includes a voltage zero. The alteration is effected by closing a switch connected across the system for the period the voltage reduction is required.
47 Citations
10 Claims
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1. In a system for transmitting information in an A.C. electricity supply system by reducing the instantaneous value of the A.C. supply voltage during the same small fractional part of each of a selection of cycles of the supply voltage waveform, said part including a time of voltage zero, a transmitter comprising:
- controllable switch means connected across said supply system in an effective zero impedance path so as to effectively shortcircuit said supply system throughout the whole of any period that the switch means is closed and thereby draw from said system throughout the whole of any period that said switch means is closed a current of sufficient magnitude to reduce the instantaneous value of the A.C. supply voltage during the time that said switch means is closed and conducting; and
switch control means for closing said switch means for a said small fractional part of any selected single cycle of the supply voltage waveform. - View Dependent Claims (2, 3, 4, 5, 6)
- controllable switch means connected across said supply system in an effective zero impedance path so as to effectively shortcircuit said supply system throughout the whole of any period that the switch means is closed and thereby draw from said system throughout the whole of any period that said switch means is closed a current of sufficient magnitude to reduce the instantaneous value of the A.C. supply voltage during the time that said switch means is closed and conducting; and
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7. In a system for transmitting information in an A.C. electricity supply system by reducing the instantaneous value of the A.C. supply voltage during the same small fractional part of each of a selection of cycles of the supply voltage waveform, said part including a time of voltage zero, a receiver comprising:
- an integrator which integrates the instantaneous value of the supply voltage system for short periods each less than the supply voltage cycle period and each starting at a zero crossing of the waveform of said voltage, the integrator being reset between successive integration periods; and
means for detecting when the output of said integrator for an integration period differs from the output of the integrator for the preceding integration period. - View Dependent Claims (8, 9, 10)
- an integrator which integrates the instantaneous value of the supply voltage system for short periods each less than the supply voltage cycle period and each starting at a zero crossing of the waveform of said voltage, the integrator being reset between successive integration periods; and
Specification