D-series connectors have been in widespread use for many years, they were originally developed by Cannon in 1952 and are now part of CanT. The D-type connector has been used in many applications as a multi-way connector, and it is best known as the connector used for RS-232 serial links. In fact, D-type connectors have been used for serial links on most computers for years, and various types of D-type connectors can still be found on most computers today.

D-type connectors were originally called subminiature connectors, and connectors are now commonly referred to as D subminiature connectors. Although these connectors were small when they were first introduced, after so many years of development in the connector industry, many sophisticated connector products have been developed and designed in the world, so D-type connectors are no longer considered true ultra-small Connector.

D-type connectors usually consist of two, and sometimes more, connecting rows in parallel. The connector has a D-format metal shell, which not only provides mechanical strength to the connector, but also provides some limited screening, the metal shell of the plug and socket contacts to provide screening. Additionally, panel mount connectors are typically secured to the panel using nuts with additional threads that allow mating connectors to be secured to them to prevent loosening.