Thursday, 23 June 2011

VGA connector



Video Graphics Array (VGA) connector .............................                                             
is a three-row 15-pin DE-15 connector. The 15-pin VGA connector is found on many video cards, computer monitors, and some high definition televisionsets. On laptop computers or other small devices, a mini-VGA port is sometimes used in place of the full-sized VGA connector.
       DE-15 is also conventionally called RGB connector, D-sub 15, mini sub D15, mini D15, DB-15, HDB-15, HD-15 or HD15 (High Density, to distinguish it from the older and less flexible DE-9 connectorused on older VGA cards, which has the same shell size but only two rows of pins).
VGA connectors and cables carry analog component RGBHV (red, green, blue, horizontal sync,vertical sync) video signals, and VESA Display Data Channel (VESA DDC) data. In the original version of DE-15 pinout, one pin was keyed and 4 pins carried Monitor ID bits which were rarely used; VESA DDC redefined some of these pins and replaced the key pin with +5 V DC power supply.
Cable quality..............
The same VGA cable can be used with a variety of supported VGA resolutions, ranging from 640×400px @70 Hz (24 MHz of signal bandwidth) to 1280×1024px @85 Hz (160 MHz) and up to 2048×1536px @85 Hz (388 MHz). There are no standards defining the quality required for each resolution, but higher-quality cables typically contain coaxial wiring and insulation which make them thicker. A quality cable should   not suffer    from signal crosstalk which occurs when the signals in one wire induce unwanted currents in adjacent wires, ghosting   which occurs when impedance mismatches cause signals to be reflected (note that ghosting   with long   cables may not be the fault of the cable but may instead be   caused by   equipment with incorrect termination or by use of passive splitters), and other signal degradation effects; shorter VGA cables are less likely to introduce significant degradation. Some higher-end monitors and video cards featured 5 separate   BNC connectors   for   RGBHVsignal, allowing highest quality connection using five 75 ohm coaxial cables.


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