Patent ID: 6639779
Filing Date: 2003-10-28
Classification: H02H,H04M

Abstract:
A frequency selective transient voltage protector connectable to a two-wire communications line upon which a signal having a voltage and a frequency may be present and comprising:a frequency discriminator connectable across the communications line, said frequency discrimination having an output and a voltage at said output related to the frequency and voltage of the signal on the communications line; a voltage discriminator connected to said output of said frequency discriminator, said voltage discriminator being in a conductive state and presenting a low impedance to said output of said frequency discriminator when a signal present on the communications line has a frequency equal to or exceeding a predetermined frequency and a voltage equal to or exceeding a first predetermined voltage, said voltage discriminator otherwise being in a nonconductive state and presenting a high impedance to said output of said frequency discriminator; and an overvoltage protection device connected to said voltage discriminator and connectable across the communications line, said overvoltage protection device being in a conductive state and presenting a low impedance to the signal present on the communications line when said voltage discriminator is in said conductive state, and being in a nonconductive state and presenting a high impedance to the signal present on the communications line when said voltage discriminator is in said nonconductive state.