What is a d-sub port?

Written by peter syslo
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What is a d-sub port?
Older printers require a 25-pin D-Sub port for connection. (Stockbyte/Stockbyte/Getty Images)

D-Sub ports are used for connecting external devices to a computer. They are an older method of connection, but some modern computers still contain them. These ports are gradually being replaced by more efficient connection technology, such as USB and FireWire.

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Computer Ports

A port is an electrical connection point on the outer surface of a computer case. Ports connect devices directly to the motherboard, or main circuit board, of a computer. Common devices that use ports are a monitor, mouse, keyboard and printer. Some ports connect a specific device, such as the VGA port for a monitor. Others, including USB ports, are "general-purpose" and can connect various devices, such as cameras, joysticks and cellphones.

D-Sub Connectors

The term "D-Sub" stands for "D-Subminiature," which is a type of connector. D-Sub connectors were created in the 1950s, and they are still used in modern computers. They are shaped like a sideways letter "D", with one side slightly longer than the other. Due to the shape, there is only one way to connect a device. All D-Sub connectors have a metal "shield" that surrounds two or more rows of pins (male) or holes (female). The number of pins or holes in D-Sub connectors can range from nine to 100.

Advantages and Disadvantages

One advantage to some D-Sub ports is that they contain threaded holes on each side that secure the screws on male D-Sub cables. This creates a solid and reliable connection. Other advantages are that the multi-pin ports allow for many wiring options and the connectors are inexpensive. The disadvantages are that the ports are large and do not contain wires/lines for power. The D-Sub port has lines for data and communication, but a connected device still requires a separate power supply. USB ports have replaced D-Sub ports because they are much smaller, wiring is more consistent and they do contain lines for powering devices.

Common D-Sub Ports

Two types of D-Sub ports are still in use. The first is the VGA, or monitor, port. It is a female D-Sub connector that contains a flat surface and fifteen holes divided into three rows. The second is the 9-pin, or DE-9, serial port. It is a female D-Sub connector that contains nine holes divided into two rows. It is called "serial" because data is transferred and received one "piece" at a time over two lines. The 9-pin serial port is a general-purpose port, and it is the type of D-Sub that has largely been replaced by the USB port.

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