| 摘要 |
PURPOSE:To always ensure the TV reception in the best condition, by giving a comparison between the wave detection output levels of the two antennas and in the vertical flyback time with every 1/60sec and then connecting the antenna having a higher level to the picture receiver. CONSTITUTION:In the switching circuit 5, a switching is carried out via the semiconductor switching element or the like so that the output of either one of the antennas 1 and 2 may be connected to the antenna input circuit of the TV picture receiver 6 installed in the car 10. Then the TV video signal Ea and the vertical synchronous signal Kb of the wave detection output are extracted out of the receiver 6 to be led to the control circuit 7. At the same time, the sampling switch control signal Ks of a fixed cycle is produced in the circuit 7 based on the reference time within the vertical flyback time TV. In this case, a comparison is given for the wave detection output levels between the antennas 1 and 2 in the vertical flyback time with every 1/60sec. And the antenna having a higher level is connected to the picture receiver. As a result, the TV reception is possible at all times in the best condition. |
