What is the standard D-sub connector used for?

The standard D-sub connector is a common type of electrical connector. They are named for their characteristic D-shaped metal shield. When they were introduced, D-subs were among the smallest connectors used on computer systems.

For example, the analog VGA monitor interface uses a D-sub 15-pin plug and socket. Also called “DB connectors” and “D-subs,” they come in 9, 15, 25, 37 and 50 pin varieties.

DB-25
The female DB-25 was widely used in the past for the printer port on a PC. The male DB-25 was also the second serial port (COM2) on the PC when serial ports were popular. It is still widely used for RS-232 communications devices.

DB-9 (DE-9)
The male DB-9 connector (officially DE-9) was typically used for the first serial port on earlier PCs (COM1) as well as other communications devices. See serial port.

DB-15 (DA-15 and DE-15)
Two DB-15 connectors are widely used. The larger, two-row female DA-15 is the game port on a PC, and the smaller, three-row, female high-density DE-15 is the VGA port. See VGA and plugs and sockets.

DC 37 connectors are commonly used in Hospital facilities as an interface between hospital beds and nurse call systems, allowing for the connection and signaling of Nurse Call, Bed Exit, and Cord out including TV entertainment and lighting controls.

The complete range of D-sub connectors also includes DA15s (one row of 7 and one of 8), DC37s (one row of 18 and one of 19), and DD50s (two rows of 17 and one of 16); these are often used in industrial products, the 15-way version being commonly used on rotary and linear encoders.