Abstract: A method of communicating over a power line is disclosed, the method comprising the step of modulating a current component of an AC power signal present on the power line. Also disclosed is a communications protocol for communication between a monitoring unit and an appliance, the protocol having two modes of operation, the first mode being an on-line single direction protocol for communications from the appliance to the monitoring unit via modulation of a current component of an AC power signal between the monitoring unit and the appliance, and the second mode being an off-line protocol for communications at least from the monitoring unit to the appliance, the second mode being operable only when the power signal is not present between the monitoring unit and the appliance.

Abstract: A flag and a method for indicating a predetermined condition in a data communications environment, such as commencement of a transmission, are disclosed. The flag has the property that self correlation of the flag provides an outcome equal to a bit length of the flag and of a first polarity when aligned, and an outcome of zero or of an opposite polarity at any unaligned position.

Abstract: The invention provides a power conversion device operable in a discontinuous conduction mode under the control of a switch. During operation in the discontinuous conduction mode, an oscillating voltage exists across the switch means prior to a turn-on of the switch means. The power conversion the device comprises a switching controller arranged to ensure that turn-on of the switch occurs at a minimum of the oscillating voltage. The power conversion device also comprises a timer arranged to provide a controlled time period following a first turn-on of the switching means, during which a second turn-on of the switching means can not occur. Such an arrangement is advantageous in that a low power level of operation of the device and a short conduction time of the switch means does not lead to an undesirable increase in switching frequency. Consequently, a reduction in a parasitic capacitance of the switch will be rewarded by an increase in efficiency.

Abstract: A method of communicating over a power line is disclosed, the method comprising the step of modulating a current component of an AC power signal present on the power line. Also disclosed is a communications protocol for communication between a monitoring unit and an appliance, the protocol having two modes of operation, the first mode being an on-line single direction protocol for communications from the appliance to the monitoring unit via modulation of a current component of an AC power signal between the monitoring unit and the appliance, and the second mode being an off-line protocol for communications at least from the monitoring unit to the appliance, the second mode being operable only when the power signal is not present between the monitoring unit and the appliance.

Abstract: The invention provides a power conversion device operable in a discontinuous conduction mode under the control of a switch. During operation in the discontinuous conduction mode, an oscillating voltage exists across the switch means prior to a turn-on of the switch means. The power conversion the device comprises a switching controller arranged to ensure that turn-on of the switch occurs at a minimum of the oscillating voltage. The power conversion device also comprises a timer arranged to provide a controlled time period following a first turn-on of the switching means, during which a second turn-on of the switching means can not occur. Such an arrangement is advantageous in that a low power level of operation of the device and a short conduction time of the switch means does not lead to an undesirable increase in switching frequency. Consequently, a reduction in a parasitic capacitance of the switch will be rewarded by an increase in efficiency.