What is DB9 connector and what are the applications of DB9 female and male connectors?

What is DB9 connector and what are the applications of DB9 female and male connectors?

Many people do not understand what is DB9 connector. In fact, DB9 connector is a common electrical connector, is one of the common D-Sub type of connectors. DB9 is the smallest model of D-Subminiature connector, DB9 female connector has 9 pin holes, while DB9 male connector is 9 pins.

In addition, DB9 connector is DE9 D-sub 9-pin connector, just incorrectly called "DB9" connector, where E is the size of the shell. For example, computer first used DB25 connector as its serial and parallel port when PC serial port started to use DE9 D-sub 9-pin connector. However, due to ignorance, it was usually labeled as DB9 instead of DE9 connector, incorrectly using B to indicate the fact of shell size. So now it is common to sell DE9 connectors as DB9 connectors, and DB9 means 9-pin connector with E size shell.