as the standard 80x25 text mode, which meant that pressing to return to text mode didn't change the frequency of the video signal, and thus the monitor did not have to resynchronize (which could otherwise have taken several seconds). Connector The standard VGA monitor interface is a 15-pin D-subminiature connector in the "E" shell, variously referred to as "HD-15", "DE-15" and "DB-15". Because VGA uses low-voltage analog signals, signal degradation becomes a factor with low-quality or overly long cables. Solutions include shielded cables, cables that include a separate internal coaxial cable for each color signal, and "broken out" cables utilizing a separate coaxial cable with a BNC connector for each color signal. BNC breakout cables typically use five connectors, one each for Red, Green, Blue, Horizontal Sync, and Vertical Sync, and do not include the other signal lines of the VGA interface. With BNC, the coaxial wires are fully shielded end-to-end and through the interconnect so that virtually no crosstalk and very little external interference can occur. Color palette The VGA color system uses register-based palettes to map colors in various bit depths to its 18-bit output gamut. It is backward compatible with the EGA and CGA adapters, but supports extra bit depth for the palette when in these modes. For instance, when in EGA 16-color modes, VGA offers 16 palette registers, and in 256-color modes, it offers 256 registers. Each palette register contain a 3×6 bit RGB value, selecting a color from the 18-bit gamut of the DAC. These color registers are initialized to default values IBM expected to be most useful for each mode. For instance, EGA 16-color modes initialize to the default CGA 16-color palette, and the 256-color mode initializes to a palette consisting of 16 CGA colors, 16 grey shades, and then 216 colors chosen by IBM to fit expected use cases. After initialization they can be redefined at any time without altering the contents of video RAM, permitting palette cycling. In the 256-color modes, the DAC is set to combine four 2-bit color values, one from each plane, into an 8-bit-value representing an index into the 256-color palette. The CPU interface combines the 4 planes in the same way, a feature called "chain-4", so that each the pixel appears to the CPU as a packed 8-bit value representing the palette index. Use The video memory of the VGA is mapped to the PC's memory via