Serial port ABCs
Serial port devices
DB9 information
DB25 information
Technical Support

SERIAL PORT ABCs

The serial port is an Asynchronous port which transmits one bit of data at a time, usually connecting to the UART Chip. Serial Ports are commonly found on the majority of PC Compatible computers. Usually referred to as a DB9 or DB25 connection, both of which adhere to the RS-232c interface standard and defined in ISO 2110 and ISO 4902. D represents the shape of the connector if placed vertically as shown in the below illustrations. The number 9 / 25 indicating the number of pins found on the connector. DB9 Serial connections are now commonly found on modern PCs where DB25 is commonly found on older computers.

SERIAL PORT DEVICES

Below is a listing of various hardware components which can be purchased and used with your Serial port.

Mouse - One of the most commonly used devices for serial ports, usually used with computers with no PS/2 Ports or laptop computers.

Modem - Another commonly used device for serial ports. Used commonly with older computers, however, is also commonly used for its ease of use.

Network - One of the original uses of the serial port, which allowed two computers to connect together and allow large files to be transferred between the two.

Printer - Today, this is not a commonly used device for serial ports (not applicable to the DB25 or Parallel Port). However, was frequently used with older printers and plotters.

DB9 INFORMATION

In the illustration below you can notice several factors to help correctly identify the DB9 Serial connection. First, you will notice that the DB9 connection has 9 pins, which are each described in the below chart. The illustration below is an example of the female serial connector which would usually be located on the connector that would connect to the computer. Each serial connector generally has two screws measuring .3 cm to allow the serial connection to be securely connected to the back of the computer.

Identifying:

The DB9 serial connection is identified first by its 9 pins.
The DB9 is shaped like a D.
The DB9 will generally be a male connector on the back of the computer.

Below is a listing of each of the pins located on the DB9 connector and what each of these pins are for.

In the illustration below you can notice several factors to help correctly identify the DB25 port. First you will notice that the DB25 connection has 25 pins which are each illustrated in the below chart.

Identifying:

The DB25 serial connection is identified first by its 25 pins.
The DB25 is shaped like a D.
The DB25 is generally be a male connector on the back of the computer.

Additional information on the DB25 port and the pins see our Parallel Port page.