D-sub connector

D-subminiature or D-sub connectors were introduced by Cannon in 1952.

See Wikipedia for details.

They were ubiquitous in computer applications from the 1960s to the early 21st century and are still in widespread use in industrial applications. Many data communication standards specify D-sub connectors, e.g V.24/RS-232 (DB-25 connector), X.21 (DA-15 connector), etc.

The D-sub series of connectors was introduced by Cannon in 1952. There are five basic shell sizes, DA through DE (see illustration). Cannon's part-numbering system used 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.

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. 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.

Originally, all versions except DD had two rows of contacts. Later, "high density" versions with extra rows were added, the most widely used of which is the familiar DE-15 VGA connector.

Special versions of D-shell connectors exist that replace some groups of contacts with coaxial or high-current inserts. Examples include the video signal connectors on 1990s Sun workstations, and the interface connectors on Tektronix SD-series sampling heads (see photos).