SOUND INTERMEDIATE FREQUENCY SIGNAL DETECTING CIRCUIT

摘要

PURPOSE:To prevent generation of buzz sound and beat sound, by multiplying the video carrier wave and the sound carrier wave to obtain a sound intermediate frequency signal. CONSTITUTION:Band filter 23 and limiter 29 are used to generate video carrier wave X1 of a fixed amplitude from the output of tuner 22. Video carrier wave X1 and sound carrier wave X2 which is taken out from the tuner output similarly by band filter 26 are multiplied to obtain sound intermediate frequency signal S3 of 4.5MHz which is differential components between both carrier waves.