Many products have arbitrary names. The name might sound nice or describe a single feature, but it won’t tell you very much about the product. D-sub connectors are a bit different. When D-subs were first invented in 1952 by ITT Cannon, the company used a special naming system to make identification simple. Today we’re going to look at how that naming system works and how common it is today, over fifty years later.
When naming D-sub connectors, the first letter is always D, but that D is followed by another letter (A, B, C, D, or E) that corresponds to the shell size. Those initials are followed by a dash and then the number of pins or sockets. Finally, there is one more letter to signify the connector’s gender, either P for plug or S for socket (sometimes M and F are used instead, for male and female).
In a connector with normal density, the shell size corresponds to a certain number of pins or sockets. For example, A contains 15, B contains 25, and C contains 37. When the connector has high density or double density, the numbers and spacing shift. More rows are added and the arrangements become denser and more crowded.
The D-sub naming system, while logical and useful, is not mandatory and over the years, some companies have accidentally (and sometimes on purpose) given their products names that don’t match up with the D-sub connector naming system. For example, when personal computers began to use 9-pin D-sub connectors with their PC serial ports, they called them DB-9 rather DE-9 because they were unaware that the second letter usually refers to the shell size.
Although the naming system isn’t used by every manufacturer, its simplicity and logic have made it very common and helped it last many, many years. A D-sub connector that doesn’t follow the system has likely been named in ignorance.