Abstract: A transponder transmitter for transmitting over power lines includes a rectifier circuit that rectifies the power at power line frequency to provide a unipolar potential having ripple at twice the power line frequency. A circuit receives a drive signal from a modulator for interrupting the unipolar potential at a rate corresponding to the carrier frequency of the modulating signal. Circuitry, including a triac couples the interrupted unipolar potential to the power lines.

Abstract: Power lines within a building or other user location are connected through a fuse and a filter to an external power grid that supplies power at the usual 50 Hz or 60 Hz. Communications apparatus such as a central computer and a number of typewriters is connected to the power lines within the building at at least two locations and transmits communications signals over the power lines. The communications signals have a frequency different from the frequency of the electrical power supplied by the external power grid and preferably in the audio range. The filter is tuned to pass the electrical power but substantially to block passage of the communications signals. Two important advantages are that the power lines within the building double as communications lines and that the building presents a purely resistive load to the external power grid, so that the grid has an improved power factor.

Abstract: A hydro-air storage system for generating electricity in which a subterranean reservoir containing water is pressurized and the water is pumped to a surface reservoir during periods when the demand for electricity is low and in which water from the surface reservoir flowing into the subterranean reservoir and compressed air released from the subterranean reservoir are both utilized to generate electricity during periods when the demand for electricity is high.