D-sub connectors are a type of electrical connector used for a variety of applications, such as computer peripherals, industrial equipment, and telecommunications. They come in two main varieties: D-subminiature (D-sub) and High-Density D-sub (HDD). D-subs feature rows of pins or sockets mounted into a D-shaped metal shell for a snug and secure connection. D-subs are commonly used for analog video and digital interfaces, such as VGA, DVI, S-Video, Firewire, and USB, as well as for carrying data and power signals between circuit boards. The various types of D-sub connectors are defined by their pin and socket configuration, shell size and contact style.