OPTICAL NETWORK UNIT AND ANNOUNCEMENT BROADCAST SYSTEM USING OPTICAL NETWORK UNIT

PROBLEM TO BE SOLVED: To obtain an optical network unit which performs announcement broadcast even if an illegal viewing function of television operates.SOLUTION: The optical network unit 6 includes: an optical conversion element 10 which converts an optical signal to an electric signal; a variable resistor 17 switches between a state of allowing all bands of a frequency-multiplexed television broadcasting signal and announcement broadcasting signal to pass, and a state of attenuating only a band of a wide band television broadcasting signal; and a first high-frequency amplifier circuit 200 which amplifies an electric signal of the all band converted by a transducer. The device further includes a control device 15 controlling a variable resistor to allow all bands to pass through when reception of a wide band television broadcasting signal is permitted while the optical network unit of the device is designated based on the control signal contained in an electric signal, and so that the variable resistor attenuates only the band of the wide band television broadcast signal to amplify the band of the announcement broadcast signal and only the control signal when the reception of the wide band television broadcast signal is not permitted.