Patent ID: 6398191
Filing Date: 2002-06-04
Classification: H05C

Abstract:
A device for an electric fence, including an electric unit, which is connectable to an electrically conducting fence and includes a voltage generator arranged to apply a relatively high electric voltage to said fence, a proximity detector, which is arranged to sense a state at which an animal is in contact with or in the proximity of said fence, and a control unit, which is connected to the voltage generator and the proximity detector and arranged to activate the voltage generator to apply said relatively high electric voltage to said fence in response to said state, wherein the control unit is arranged to initiate said sensing discontinuously during relatively short recurrent time periods, characterized in that the proximity detector is arranged to detect said state by sensing an electric parameter substantially dependent on the capacitance between said fence and ground, wherein:the proximity detector includes a signal generator generating a signal of a determined frequency; the proximity detector forms a circuit, including the capacitance of said fence to ground and a resistance in series with the capacitance; proximity detector is arranged to conduct said signal from the signal generator via the resistance and a conduit to the fence; and the proximity sensor includes a phase detector arranged to detect said state by comparing the phase position of the signal generated by the signal generator and the signal at the conduit.