| 摘要 |
PURPOSE:To automatically switch a receiving antenna, by providing a switch ing circuit for switching a video signal from the antenna, a sample holding circuit for sampling a pedestal level, and a comparing circuit for comparing a signal level. CONSTITUTION:A high frequency video signal received by an antenna is inputted to a television receiver 42 through a high frequency switch 37, samples a pedestal level of a video signal 43 by a level sampling circuit 44, and after that, is converted to DC voltage by a peak holding circuit 51. The highest level signal and other signal by a level comparing circuit 58 are outputted as an on-signal and an off-signal, respectively, are held until the next level comparing time, a driving signal of the high frequency switch 37 in case of sampling a level, and an output signal for comparing a level are synthesized by a controlling circuit 63, become driving signals 38, 39 and 40, and the high frequency switch 37 is controlled. In this way, the antenna is switched by a simple constitution. |
