If we use the TV set in our life, the modulator outputs the video signal and audio signal of our digital TV set-top box or satellite digital television receiver and modulates the signal from the TV set-top box or receiver, that is, the input. When it is an audio and video signal, it becomes a high frequency signal of a specific frequency band that is modulated at the time of output. Modulators that may be used for different sources may vary. If non-matching modulators and sources are used, character tailing may occur, so it is advisable to ask about the correlation before installing the modulator. People.