D-Sub is a family of plugs and sockets widely used in communications and on earlier PCs. For example, the analog VGA monitor interface uses a D-sub 15-pin plug and socket. Also called "DB connectors" and "D-subs," they come in 9, 15, and 25 pin varieties. The D-sub designation defines the physical structure of the connector, not the purpose of each line. BigCatCables.com offers a variety of D-Sub tool for your installation needs.