D-Sub is also called VGA (Video Graphics Adapter) interface, because it looks like a capital letter D vertically, so it is called D-Sub. D-sub is the abbreviation of D-subminiature, which is a standard of interface shape and structure. It was invented by ICC in 1952. Used to transmit analog signals, there are different number of interfaces according to requirements. Since this kind of interface was already considered small at the time, it was named after subminiature. D-sub contains several subclasses, such as DB25, the first letter D indicates that it belongs to D-sub, and the second letter B is the size of the description interface - corresponding to the following numbers (pins) (A=15 pins, B =25 stitches, C=37 stitches, D=50 stitches, E=9 stitches). Each interface is divided into male (plug) and female (socket).
1 Basic introduction
The VGA terminal (other names include RGB terminal, D-sub 15, or mini D15) is a DE-15 with 3 rows of 15 pins. VGA terminals are usually used in computer graphics cards, monitors and other devices.
Generally speaking, the 9th pin is not connected, but for the new DDC1-supporting connection, the 9th pin will be used, so the older monitors will not work properly.
2 Purpose
The most common are DB25 and DE9. Typical applications on personal computers are VGA (DA15 female), parallel port (DB25 female), COM serial (DE9 male), although these interfaces are being replaced by DVI, HDMI, RJ45 Ethernet ports. and USB replaced. After the popularity of personal computers, DE9 was misread as DB9. Over time, DB9 has become an alias for DE9. The same is true for D-subs with other needles. Now, DB9 is used relatively more.
D-sub only describes the connection structure, and does not define the role of the entire interface or all pins.
3 D-Sub for VGA
The information processed by the graphics card is ultimately output to the monitor. The output interface of the graphics card is the bridge between the computer and the monitor, which is responsible for outputting the corresponding image signal to the monitor. CRT monitors can only accept analog signal input due to design and manufacturing reasons, which requires the graphics card to be able to input analog signals. The VGA interface is the interface for outputting analog signals on the graphics card. The VGA (Video Graphics Array) interface is realized by a 15-pin D-Sub interface (DA15). Although LCD monitors can directly receive digital signals, many low-end products use VGA interfaces in order to match with VGA interface graphics cards. The VGA interface is a D-type interface with a total of 15 pins on it, divided into three rows, five in each row. The VGA interface is the most widely used interface type on graphics cards, and most graphics cards have this interface. Some graphics cards that do not have a VGA interface but have a DVI interface can also convert the DVI interface to a VGA interface through a simple adapter. Usually, graphics cards without a VGA interface will come with such an adapter.
Each pixel on the LCD screen is driven by a specific digital signal, so the LCD driven by the pure digital signal transmitted by the DVI interface will theoretically display images without any loss of detail. On the contrary, the analog signal transmitted by the D-SUB interface must be converted to output the digital signal, so image distortion is inevitable.
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