Abstract: A portable unit, preferably adapted for plugging into a common wall outlet, has circuitry for monitoring the voltage and/or current provided through an electrical outlet. In addition to the monitoring circuitry, the unit preferably includes a microprocessor for digitally processing the power waveform as well as analytical quantities related to the waveform. Further, the unit preferably has a storage area for storing samples of the input waveform as well as a log of related analytical quantities for downloading to a computer, local area network, or other destination, for collection and analysis. Preferably, the unit is provided with a local visual display and an alarm indicator.

Abstract: An apparatus to establish bi-directional digital communication over a power line network includes a signal launching circuit to impose a digital communication signal onto a power signal carried by a power line network and thereby form a digital communication power signal at a first point in the power line network. The signal launching circuit is configured to position a pulse of the digital communication signal at any phase location of each half cycle of the power signal. A receiver reads the digital communication power signal at a second point in the power line network. A signal processor is connected to the receiver to recover the digital communication signal from the digital communication power signal.