The D-type range of connectors has been in widespread use for many years. They were first developed in 1952 by Cannon which is now part of ITT. The D-type connector has been used in many applications as a multi-way connector, but it is probably most widely known as the connector used for RS-232 serial links. In fact the D-type connector was used for the serial link on most computers for many years, and today variations of D-type connectors are still found on most computers.
The D-type connector was originally termed a sub-miniature connector, and often today the connectors may be referred to as D sub-miniature connectors. Although these connectors were small when they were first introduced, the can no longer be thought of as true sub-miniature connectors.
D-type connector mechanical outline
D-type connectors most commonly consist or two parallel rows of connections. As there is an odd number of pins in each D-type connector, one row has one more pin than the other. This basic construction is used for the more common configurations of connector, namely 9, 15, 25, and 37 way connectors. High pin counts and higher pin densities can be achieved using more rows of pins.
The pins in the D-type connector are surrounded by a metal shield or casement that provides mechanical support and protection and this also provides some degree of electromagnetic shielding that can help reduce radiated interference and pickup levels. This metal surround is broadly in the shape of a D and this gives the connector its name. It also ensures the correct orientation of the plug when mating
The pins in the more common connector types with two rows of pins (e.g. 9, 15, 25 and 37 way) are spaced approximately 0.108 inch (2.74 mm) apart with the rows spaced 0.112 inch (2.84 mm) apart.
D-type connector numbering
The part numbering system for the D-type connector uses a D as the prefix for the whole series. This is followed by a letter denoting the shell size (A=15 pin, B=25 pin, C=37 pin, D=50 pin, E=9 pin), followed by the actual number of pins, followed by the gender (F = female, M = male). Thus a connector with a part number of DE9S indicates a D-type connector with a 9 way shell size, 9 contacts and in the form of a socket.