A DVI connection can be one of three types - DVI-I, DVI-D or DVI-A.
DVI-I:
DVI-I contains both the digital and analog connections, (DVI-D + DVI-A) , it's essentially a combination of DVI-D and DVI-A cables within one cable.
DVI-D:
DVI-D (like DFP or P&D-D (EVC)) is a digital only connection. If both devices being connected support a Digital DVI connection (DVI-I or DVI-D compatible) and are compatible in resolutions, refresh rates and sync, using a DVI-D cable will ensure that you are using a digital connection rather than an analog connection, without playing around with settings to assure this.
DVI-A:
DVI-A is really rare. Why use a DVI connector when you can use a cheaper VGA connector? see DVI-I P&D-A (EVC) is more common with projectors, and you should go to your projector manufacturer for recommendations.
Dual Link: Dual T.D.M.S. (transition minimized differential signaling) "links". DVI can have up to two TMDS links. Each link has three data channels for RGB information with a maximum bandwidth of 165 MHz, which is equal to 165 million pixels per second. Dual-link connections provide bandwidth for resolutions up to 2048 x 1536p.
Single Link: Single T.D.M.S. link. Each link has three data channels for RGB information with a maximum bandwidth of 165 MHz, which is equal to 165 million pixels per second.
Bandwidth for a single-link connection supports resolutions of over 1920 x 1080 at 60 Hz (HDTV).
Dual link vs Single Link: Don't believe the "hype" some websites are using about dual link cables being superior to single link cables. A single link cable is 100% as good as a dual link cable for single link equipment which covers about 99.5% of current equipment, including HDTV's, Projectors, Plasma Screens, and High
Definition Set top Boxes. A better quality cable is a better quality cable, and single and dual link has nothing to do with quality. On the other hand, if both devices being connected support Dual links, then a dual link cable is the proper cable for the application, and you will have the capability of much greater resolutions and refresh rates. A properly designed Dual link cable should have no negative effects when used with single link equipment.
*Whether or not you need Dual Link or Single link will depend on your equipment.
*SEE PICTURES BELOW*
This is a DVI-I "Dual Link" or "Single Link" female connector. This should work with DVI-I, DVI-A or DVI-D devices with "Dual Link" or "Single Link" connections. If both devices use this connector, use a "Dual Link" connector. DVI-D Connector
You must use a DVI-D cable.
Adapters:
DVI to VGA adapters (really DVI-A to VGA adapters) will connect a regular VGA/SVGA monitor to a DVI-I connection.
A DVI-I connection from a video card or monitor will connect to a digital signal (DVI-D) and an analog signal (VGA) as well. Connecting DVI-D or DFP or D&P-D connections to a VGA monitor requires a digital to analog converting adapter, which currently cost around $400.00, usually making a video card replacement a better choice.