Patent ID: 6212365
Filing Date: 2001-04-03
Classification: H04B

Abstract:
Circuit for selectively enabling communications by providing an output signal voltage of a first level indicative of a first transmission state and a second level corresponding to a second non-transmission state according to the magnitude and polarity of an applied input signal voltage, said circuit comprising:a FET having gate, source, and drain electrodes, said source electrode coupled to a first control means for providing an input voltage Vs to said source, said drain electrode coupled to an output terminal of said circuit for providing said output signal, and said gate electrode coupled to a second control means for providing a voltage Vg to said gate,said FET operable in a first conducting mode when a gate to source voltage Vgs exceeds a predetermined threshold, indicative of a non-zero crossing amplitude region of said input signal voltage, to cause said output signal voltage to be at said second level corresponding to the non-transmission state, andin a second non-conducting mode, wherein said Vgs of said FET is less than said threshold, indicative of a zero-crossing of said input signal voltage, for causing said output signal voltage to be at said first level, indicative of said transmission state,wherein said first and second control means responsive to said input voltage signal operate to vary said FET gate to source voltage for controlling current paths through said circuit to cause said FET to selectively operate in said conducting and non-conducting modes according to the magnitude and polarity of the input signal voltage.