For the trade union in New York, see District Council 37. The D-subminiature or D-sub is a common type of electrical connector. They are named for 9 pin d-sub patch cable characteristic D-shaped metal shield.
When they were introduced, D-subs were among the smallest connectors used on computer systems. A D-sub contains two or more parallel rows of pins or sockets usually surrounded by a D-shaped metal shield that provides mechanical support, ensures correct orientation, and may screen against electromagnetic interference. The part containing pin contacts is called the male connector or plug, while that containing socket contacts is called the female connector or socket. The D-sub series of connectors was introduced by Cannon in 1952. Later D-sub connectors added extra pins to the original shell sizes, and their names follow the same pattern. For example, the DE-15, usually found in VGA cables, has 15 pins in three rows, all surrounded by an E size shell. The pins are spaced at 0.
However, this naming pattern is not always followed. Because personal computers first used DB-25 connectors for their serial and parallel ports, when the PC serial port began to use 9-pin connectors, they were often labeled as DB-9 instead of DE-9 connectors, due to an ignorance of the fact that B represented a shell size. DB-44HD, DB-62HD, and DB-78HD connectors, respectively, where HD stands for high density. Cannon also produced “combo” D-subs with larger contacts in place of some of the normal contacts, for use for high-current, high-voltage, or co-axial inserts. A further family of connectors of similar appearance to the D-sub family uses names such as HD-50 and HD-68, and has a D-shaped shell about half the width of a DB25.
They are common in SCSI attachments. The United States military also maintains another specification for D-subminiature connectors, the MIL-DTL-24308 standard. A smaller type of connector derived from the D-sub is called the microminiature D, or micro-D, which is a trademark of ITT Cannon. It is about half the length of a D-sub and its primary application is space-grade technology. They also have threaded sockets to receive jackscrews on the cable shell, holding the plug and socket together.
The widest application of D-subs is for RS-232 serial communications, though the standard did not make this connector mandatory. RS-232 devices originally used the DB25, but for many applications the less common signals were omitted, allowing a DE-9 to be used. The standard specifies a male connector for terminal equipment and a female connector for modems, but many variations exist. Many uninterruptible power supply units have a DE-9F connector on them in order to signal to the attached computer via an RS-232 interface. Often these do not send data serially to the computer but instead use the handshaking control lines to indicate low battery, power failure, or other conditions. DE9 connectors were used for some token ring networks as well as other computer networks.