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DB9 Connector

DB9 Connector
  • DB9 is a commonly known connector used in Serial Asynchronous Data Transmission that are are designed to work with the EIA/TIA 232 serial interface standard. RS-232 (Recommended Standard 232) is the standard for establishing serial data transfer between DTE(Data Terminal Equipment) and DCE(Data Circuit-terminating Equipment).

  • The D-sub series of connectors was invented by ITT Cannon in 1952.

  • The letter A to E denotes the shell size, followed by the number of pins. Male(M) or Female(F) denotes the gender of the part.

  • DB9 Connector

  • Each shell size corresponds to a certain number of pins or sockets i.e. A with 15, B with 25, E with 9, etc. For example, DB-25 denotes a D-sub with a 25-position shell size and a 25-position contact configuration. In DB9 it denotes 9 position shell and 9 contact terminals.

  • Types of DB Connector

  • The DB style connector is a common connector used in many computer, audio/video, and data applications.The connector gets its name from its trapezoidal shape that resembles the letter "D".

  • In the name, DB stands for D-Sub-miniature or D-sub but its actual name is DE-9. Db-xx is now commonly used for all serial connectors and in today's market DE-9 connectors are sold as DB-9 connectors which instead of its correct terminology.

  • A DB9 connector has 9 pins arranged in two rows as shown in figure having 5 pins in top row and remaining in the bottom.

  • It is also known as COM port and is used to interface device with data rate less than 20kbps.

  • DB9 ports were common earlier but now with introduction to usb, firewire, etc newer computers are being built without DB9 connectors. DB9 male connector were commonly used in PC.

  • DB9 connector supports full-duplex data transfer.

  • Earlier Apple Macintosh models used DE9. Due to its large size and high manufacturing cost miniature DIN connectors are used.

  • DB9 to Mini DIN Connector

  • There are DB9-DB25 adapters/converters for easy conversion of a DB9 into DB25 connection, and vice versa. Similarly, converters for DB9 to other kinds of connectors are available.

  • DB9 to DB25 Connector

    Pin Description

    Pin number Name Abbrevation Direction
    1 Carrier Detect(Received line signal detector) CD In
    2 Receive Data RXD/RX/RD In
    3 Transmit Data TXD/TX/TD Out
    4 Data Terminal Ready DTR Out
    5 Signal Ground GND -
    6 Data Set Ready DSR In
    7 Request To Send RTS Out
    8 Clear To Send CTS In
    9 Ring Indicator RI In
      Shield - -

    Below Diagram shows pin Description of DB9 Male connector: DB9 Connector Pin Diagram

    Electrical specifications

    1. Operation voltage: 250 VAC max
    2. Current rating: 3 Amps max
    3. Contact resistance: 20 mOhms max
    4. Insulation resistance: 3000 MOhms min at 1000 VDC between
    5. Dielectric withstanding voltage: 1000 VAC min rms (sea level)
    NOTE: This specifications changes with different manufacturers, requirements, etc.


  • In old generation PC's for connecting other peripheral devices.

  • They were used in Keyboard, mice, joysticks.

  • DB9 Connector are used in microprocessors evaluation board and other circuit boards for programming through PC.

  • Modem and network.

  • Stepper motor and Servo motor interface.

  • DB9 Connector with Evaluation Board DB9 Connector with Servo Amplifier DB9 Connector with Evaluation Board
    DB9 Connector with Evaluation Board DB9 Connector with Stepper Motor DB9 Connector with Stepper Motor

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