The D-subminiature or D-sub is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on personal computer systems.
Description, nomenclature, and variants
Normal density High density Double density Name Pin layout Name Pin layout Name Pin layout DA-15 8–7 DA-26 9–9–8 DA-31 10–11–10 DB-25 13–12 DB-44 15–15–14 DB-52 17–18–17 DC-37 19–18 DC-62 21–21–20 DC-79 26–27–26 DD-50 17–16–17 DD-78 20–19–20–19 DD-100 26–25–24–25 DE-9 5–4 DE-15 5–5–5 DE-19 6–7–6 19-pin 10–9 104-pin 21–21–21–21–20 23-pin 12–11 Note that the high density and double density classification here is the reverse of floppy disk nomenclature. Here, high density is intermediate, between nominal and double density.
A D-sub contains two or more parallel rows of pins or sockets usually surrounded by a D-shaped metal shield, or shell, that provides mechanical support, ensures correct orientation, and may screen against electromagnetic interference. Calling that shield a shell (or D-shell) can be ambiguous, as the term shell is also short for the cable shell, or backshell. D-sub connectors have gender: parts with pin contacts are called male connectors or plugs, while those with socket contacts are called female connectors or sockets. The socket's shield fits tightly inside the plug's shield. Panel-mounted connectors usually have #4-40 UNC (as designated with the Unified Thread Standard) jackscrews that accept screws on the cable end connector cover that are used for locking the connectors together and offering mechanical strain relief, and can be tightened with a 3/16" (or 5mm) hex socket.
The hexagonal standoffs (4-40 bolts) at both sides of each connector have a threaded stud fastening the connectors to the metal panel. They also have threaded sockets to receive jackscrews on the cable shell, holding the plug and socket together.
Occasionally the nuts may be found on a cable end connector if it is expected to connect to another cable end (see the male DE-9 pictured). When screened cables are used, the shields are connected to the overall screens of the cables. This creates an electrically continuous screen covering the whole cable and connector system.
The D-sub series of connectors was introduced by Cannon in 1952. Cannon's part-numbering system uses D as the prefix for the whole series, followed by one of A, B, C, D, or E denoting the shell size, followed by the number of pins or sockets, followed by either P (plug or pins) or S (socket) denoting the gender of the part. Each shell size usually (see below for exceptions) corresponds to a certain number of pins or sockets: A with 15, B with 25, C with 37, D with 50, and E with 9. For example, DB-25 denotes a D-sub with a 25-position shell size and a 25-position contact configuration. The contacts in each row of these connectors are spaced 326/3000 of an inch apart, or approximately , and the rows are spaced apart; the pins in the two rows are offset by half the distance between adjacent contacts in a row. This spacing is called normal density. The suffixes M and F (for male and female) are sometimes used instead of the original P and S for plug and socket.
Variants
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 horizontally and vertically, in what is called high density. The other connectors with the same pin spacing are the DA-26, DB-44, DC-62, DD-78 and 104-pin. They all have three rows of pins, except the DD-78 which has four, and the 104-pin which has five rows. The double density series of D-sub connectors features even denser arrangements and consists of the DE-19, DA-31, DB-52, DC-79, and DD-100. These each have three rows of pins, except the DD-100, which has four.
Common misnomers The above naming pattern was 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 mislabeled as DB-9 instead of DE-9 due to ignorance of the fact that B represented a much larger shell size. It is now common to see DE-9 connectors sold as "DB-9" connectors. DB-9 nearly always refers to a 9-pin connector with an E-size shell. The non-standard 23-pin D-sub connectors for external floppy drives and video output on most of the Amiga computers are usually labeled DB-23, even though their shell size is two pins smaller than ordinary DB sockets. Several computers also used a non-standard 19-pin D-sub connector, sometimes called DB-19, including Macintosh (external floppy drive), Atari ST (external hard drive), and NeXT (Megapixel Display monitor and laser printer).
Reflecting the same confusion of the letters DB with just D as mentioned above, high-density connectors are also often called DB-15HD (or even DB-15 or HD-15), DB-26HD (HD-26), 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. The DB13W3 variant was commonly used for high-performance video connections; this variant provided 10 regular (#20) pins plus three coaxial contacts for the red, green, and blue video signals. Combo D-subs are currently manufactured in a broad range of configurations by other companies. Some variants have current ratings up to 40 A; others are waterproof and meet IP67 standards.
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 DB-25. They are common in SCSI attachments.
The original D-sub connectors are now defined by an international standard, IEC 60807-3 / DIN 41652. The United States military also maintains another specification for D-subminiature connectors, the MIL-DTL-24308 standard.
Micro-D and Nano-D
Smaller connectors have been derived from the D-sub including the microminiature D (micro-D) and nanominiature D (nano-D) which are trademarks of ITT Cannon. Micro-D is about half the length of a D-sub and Nano-D is about half the length of Micro-D. Their primary applications are in military and space-grade technology such as SpaceWire networks. The MIL-SPEC for Micro-D is MIL-DTL-83513 and for Nano-D is MIL-DTL-32139.
Typical applications
Communications ports The widest application of D-subs is for RS-232 serial communications. RS-232 devices used the DB-25 as far back as the Bell 103 modem in 1967 (though the Teletype Model 33 was the most common ASCII RS-232 device, its signal interface was an internal Molex connector). The 1969 RS-232-C standard recommended the DB-25 female connectors for DTE and DCE devices, and male-to-male cables to connect them; this was codified in EIA-232D. The timesharing era from the mid-1960s to the early 1980s relied heavily on minicomputers, modems, printers, and video-display terminals connected by DB-25 cables.
As the EIA-232 standard improved, many of its defined signals became obsolete. Handshaking and secondary channel pins were not used, making a B-size connector unnecessarily large for two signal wires and ground. Vendors gradually moved away from the DB-25 to the more compact DE-9 for serial communications, and adopted standards other than EIA-232-D. The conventions for use of DB-25 eroded: the original IBM PC, and therefore many compatibles, used a DB-25 male connector at the device and a male-to-female cable to a modem, while using a female DB-25 connector as a parallel port (instead of the bulkier Centronics port found on the printer itself). Early Apple Macintosh models used DE-9 connectors for RS-422 multi-drop serial interfaces (which can operate as RS-232). Later Macintosh models use 8-pin miniature DIN connectors instead, while the IBM PC/AT switched to DE-9M connectors for serial communications.
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. Such usage is not standardized between manufacturers and may require special cables.
Network ports DE-9 connectors were used for some Token Ring networks as well as other computer networks.
Originally in the 1980s Ethernet network interface cards or devices were connected using Attachment Unit Interface (AUI) cables to Medium Attachment Units that then connected to 10BASE5 and later 10BASE2 or 10BASE-T network cabling. The AUI cables used DA-15 connectors albeit with a sliding latch to lock the connectors together instead of the usual hex studs with threaded holes. The sliding latch was intended to be quicker to engage and disengage and to work in places where jackscrews could not be used for reasons of component shape.
In vehicles, DE-9 connectors are commonly used in Controller Area Networks (CAN): female connectors are on the bus while male connectors are on devices.
Computer video output
DE-9 connectors A female 9-pin connector on an IBM compatible personal computer may be a digital RGBI video display output such as MDA, Hercules, CGA, or EGA (rarely VGA or others). Even though these all use the same DE-9 connector, the displays cannot all be interchanged and monitors or video interfaces may be damaged if connected to an incompatible device using the same connector.
+ 9-pin connector pinouts Adaptor MDA CGA EGA VGA Pin 1 Ground Ground Ground + Analog red Pin 2 Ground Ground + Secondary red (intensity) + Analog green Pin 3 + Red + Red + Analog blue Pin 4 + Green + Green − Horizontal sync. (31.5 kHz) Pin 5 + Blue + Blue ± Vertical sync. (70 / 60 Hz) Pin 6 + Intensity + Intensity + Secondary green (intensity) Red ground Pin 7 + Video Reserved + Secondary blue (intensity) Green ground Pin 8 + Horizontal sync. (18.43 kHz) + Horizontal sync. (15.7 kHz) + Horizontal sync. (15.7 / 21.85 kHz) Blue ground Pin 9 − Vertical sync. (50 Hz) + Vertical sync. (60 Hz) ± Vertical sync. (60 Hz) Combined sync ground
DE-15 connectors Later analog video (VGA and later) adapters generally replaced DE-9 connectors with DE-15 high-density sockets (though some early VGA devices still used DE-9 connectors). DE-15 connectors have the same shell size as DE-9 connectors (see above). The additional pins of the DE-15 VGA connector were used to add increasingly sophisticated monitor-sensing plug and play functionality.
DA-15 connectors Many Apple Macintosh models, beginning with the Macintosh II, used DA-15 sockets for analog RGB video out. These connectors had the same number of pins as the above DE-15 connectors, but used the more traditional pin size, pin spacing, and size shell of the DA-15 standard connector. "VGA adapters" (i.e. DA-15 to DE-15 dongles) were available but sometimes monitor-specific, or they needed DIP switch configuration, as the Macintosh's monitor sense pinsTechnical Note HW30 Sense Lines in particular were not identical with a VGA connector's DDC.
The earlier Apple IIGS used the same physical DA-15 connector for the same purpose but with an incompatible pinout. A digital (and thus also incompatible) RGB adapter for the Apple IIe also used a DA-15F. The Apple IIc used a DA-15F for an auxiliary video port which was not RGB but provided the necessary signals to derive RGB.
Game controller ports
DE-9 connectors