Patent ID: 8077879

Claim:
A television broadcast receiver for receiving a television broadcast signal for displaying a video of a video signal based on the television broadcast signal on a screen and outputting an audio of an audio signal based on the television broadcast signal from a speaker, comprising: an audio output apparatus supplied with an audio signal for applying signal processing to the audio signal and outputting a resultant signal to a speaker, said audio output apparatus comprising: a supply circuit supplied with a supply voltage from an external commercial power supply through an AC cord for generating various voltages based on the supply voltage and supplying the voltages to respective components of the television broadcast receiver; an audio circuit amplifying an audio signal input thereto in accordance with a volume control signal of 0-5V output from a microcomputer and outputting the audio signal to a speaker when a high voltage signal is input thereto, and stopping the outputting of the audio signal when a mute signal being a low voltage signal is input thereto; a protect circuit coupled with an output line of said supply circuit for outputting a protect signal represented by a low voltage signal when the output voltage of said supply circuit is decreased below a predetermined value; the microcomputer controlling said audio circuit to amplify the audio signal and outputting, upon receipt of the protect signal from said protect circuit, a mute signal to said audio circuit; and a diode disposed to connect a line through which the protect signal from said protect circuit is output and a line connecting said microcomputer and said audio circuit, such that a cathode side thereof is turned toward the line through which the protect signal is output; when the output voltage of said supply circuit begins to decrease, said protect circuit detects the decrease and outputs the low voltage signal as the protect signal, the line connecting said microcomputer and said audio circuit is pulled to low voltage substantially identical to the level of the protect signal thorough said diode, so that the mute signal being the low voltage signal is input to the audio circuit to mute the audio circuit.