It is often necessary to connect a large-screen color TV with only a coaxial RCA input socket to the VGA interface of a computer or other device for use as a display. The solution is to configure an interface converter. The circuit in the figure acts as a conversion bridge between two different interfaces. The
　　
　　VGA interface outputs the three primary color signals R, B, and G, respectively, coupled to the RCA output port through the C1C2, C3C4, and C5C6 circuit groups, and the coupling capacitor cuts off the DC component from the video card. The ICa and ICb XOR gates (74HC86) synthesize the horizontal and field synchronization separation signals into a composite synchronization signal, which is output to the synchronization signal phase conversion circuit of the DOS and Wincdow operating systems composed of the S1 bidirectional toggle switch and the field effect transistor T1. Since the composite synchronization signal and the green primary color signal are on the same channel, the brightness of the display screen will be too strong. Therefore, the resistance value of R2 can be slightly reduced to reduce the brightness, and the resistance values ​​of R1 and R3 can be appropriately adjusted to balance the three primary colors. But be careful not to overload the video card and cause overheating. The input voltage of the power regulator IC2 cannot be lower than 9V. To ensure that the converter can maintain a constant 5V operating voltage and 30mA operating current. D2 is a DC power supply polarity reverse protection diode.
　　
　　The circuit board is installed in a shielded box with a metal shell and grounding to prevent external electromagnetic field interference.