Communication via an electricity supply main
First Claim
1. A control system for remotely controlling at least one alternating current electric-mains-operated appliance, including:
- a controller having electronic switch means for superimposing a control signal on an alternating current mains supply by interrupting the mains supply for a period adjacent a zero crossing in one or more selected half-cycles of the mains supply and substantially less than the mains supply cycle period thereby to hold the mains supply voltage substantially at zero during said interruption;
at least one receiver means for monitoring the mains supply and for controlling said electrical appliance said receiver having(A) interruption detector means including a full wave rectifier means for providing a full-wave rectified signal from said mains supply;
voltage threshold detector means for receiving said full-wave rectified signal and producing an output whenever the voltage of said full-wave rectified signal is lower than a threshold voltage; and
means for responding to the durations of said outputs from said voltage threshold detector means to produce an indication of the occurrence of a said interruption; and
(b) means responsive to said indications of the occurrence of an interruption to produce outputs for controlling said electric appliance in accordance with the control signal from the controller.
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Accused Products
Abstract
Control signals are transmitted through a.c. mains supply lines to control operation of electrical equipment powered from the supply lines. A near short-circuit condition is introduced across the a.c. mains supply lines, for example, by firing a thyristor connected in series with a fuse across the supply lines, for the final portion of positive half cycles of the mains supply voltage, thus holding the voltage to a near zero value for this length of time. A receiver coupled to the mains supply lines includes a zero crossing detector circuit which responds to the near zero voltage conditions across the supply lines to perform a particular control operation on an associated appliance connected to the receiver. Different control operations may be effected by defining the control signals over a group of half cycles of the a.c. supply mains and selecting one or more half cycles of the group during which the supply voltage is reduced to the near zero level, thereby producing a sequence of selected and non-selected half cycles within the group so that by changing the sequence the particular control operation can be changed accordingly.
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Citations
6 Claims
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1. A control system for remotely controlling at least one alternating current electric-mains-operated appliance, including:
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a controller having electronic switch means for superimposing a control signal on an alternating current mains supply by interrupting the mains supply for a period adjacent a zero crossing in one or more selected half-cycles of the mains supply and substantially less than the mains supply cycle period thereby to hold the mains supply voltage substantially at zero during said interruption; at least one receiver means for monitoring the mains supply and for controlling said electrical appliance said receiver having (A) interruption detector means including a full wave rectifier means for providing a full-wave rectified signal from said mains supply;
voltage threshold detector means for receiving said full-wave rectified signal and producing an output whenever the voltage of said full-wave rectified signal is lower than a threshold voltage; and
means for responding to the durations of said outputs from said voltage threshold detector means to produce an indication of the occurrence of a said interruption; and(b) means responsive to said indications of the occurrence of an interruption to produce outputs for controlling said electric appliance in accordance with the control signal from the controller.
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2. A control system for remotely controlling one or more alternating current electric-mains-operated appliances, including:
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a controller having electronic switch means for superimposing a control signal on an alternating current mains supply by interrupting the mains supply for a period adjacent a zero crossing in one or more selected half-cycles of a group of half-cycles of the mains supply and substantially less than the mains supply cycle period thereby to hold the mains supply voltage substantially at zero during the or each said interruption for producing a control signal comprising a sequence of selected and non-selected half-cycles in said group, the particular sequence characterizing an individual control signal; at least one receiver means for monitoring the mains supply and for controlling the or each electrical appliance to which it is connected;
said receiver having;(A) interruption detector means including a full wave rectifier means for providing a full-wave rectified signal from said mains supply;
voltage threshold detector means for receiving said full-wave rectified signal and producing an output whenever the voltage of said full-wave rectified signal is lower than a threshold voltage; and
means for responding to the duration of said outputs from said voltage threshold detector means to produce an indication of the occurrence of a said interruption; and(B) means responsive to said indication of the occurence of an interruption to produce outputs for controlling said electric appliance in accordance with the control signal from the controller. - View Dependent Claims (3, 4, 5, 6)
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Specification