How to Convert RJ11 to DB9

Written by dave wilson
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How to Convert RJ11 to DB9
Build a DB9 to RJ11 adaptor to connect to a Sun StorEdge T3 Disk Tray, (serial adaptor image by Paul Moore from

RJ11 connectors are most commonly used in phones and wall jacks of standard landline telephone systems. However, the Sun StorEdge T3 Disk Tray device requires an RJ11 serial connection with special pinouts for configuration and maintenance. Windows PC serial ports have DB9 female connectors, so they cannot directly connect to the serial port on a Sun StorEdge T3 Disk Tray. Users must make this connection with a properly configured RJ11 to DB9 converter. Build an RJ11 to DB9 converter according to the pinouts required to communicate with a Sun StorEdge T3 Disk Tray unit.

Skill level:

Things you need

  • RJ11-6 female to DB9 male adaptor kit
  • RJ11-6 cable with six pins

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  1. 1

    Disassemble the RJ11 to DB9 adaptor kit by loosening and removing the screws that secure the cover in place. Remove the DB9 connector from the cover. Unsnap the connector halves to remove the RJ11 connector and wires.

  2. 2

    Note the small numbers printed next to each pin hole on the back of the DB9 connector. Place each wire from the RJ11 connector into a pin hole in the back of the DB9 connector following the pinout below:

    RJ11 Pin 1 to DB9 Pin 1

    RJ11 Pin 4 to DB9 Pin 5

    RJ11 Pin 5 to DB9 Pin 3

    RJ11 Pin 6 to DB9 Pin 2

    Note that the RJ11 pins must be counted from left to right with the socket facing toward you and the tab slot down.

  3. 3

    Position the RJ11 to DB9 wired assembly onto one of the connector cover halves. Position the other connector cover half on the opposite side of the connectors and tuck in the wires. Snap the connector halves in place and secure with the connector cover screws.

  4. 4

    Plug the six pin RJ11 cable into the RJ11 connector on the RJ11 to DB9 adaptor. The RJ11 to DB9 converter is now ready for use.

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