Piezo-electric terminal station for communications system

Claim 1

A terminal station for communication via a pair of mains wires said terminal station comprising: a piezo-electric coupler of a circular configuration and of a disc-like shape wherein said thickness is significantly less than said diameter, said disc having on both major surfaces central disc electrodes each surrounded by outer concentric annular electrode with the outer electrode manifesting an input port for the terminal station and with the inner central electrodes manifesting an output port, said coupler dimensioned to have a resonant frequency within the range of 40-140 KHz, according to the diameter of said disc, means coupling the inner central electrodes to said pair of mains wires, a modulator having an input adapted to receive an input signal for providing at an output a modulation control signal, an oscillator having an input coupled to the output of said modulator for providing at an output a modulated signal of a frequency according to the resonant frequency of said coupler, with the output of said oscillator coupled to the input of a coupler driver having an output coupled to one of said outer electrodes, with said other outer electrode coupled to a point of reference potential to activate said coupler to transmit modulated signals to said mains wires with the output of said coupler driver further connected to one input of a differential receive amplifier for receiving modulated signals, a demodulator coupled to the output of said receive amplifier for demodulating received signals and means connected between said demodulator and said coupler driver to disable said driver when modulated signals are being received from said mains.