Cable Spec 1 - RJ-45 to DB9 Female - "ST" or Straight Through adapter for all applications except for the CB-EL1 board
Written by Michael Cone
Updated at January 25th, 2026
Table of Contents
Spec for RJ-45 Female to DB-9 Female Adapter - "ST" or Straight Through
This is the original RJ-45 to DB-9 conversion spec. It is good for all applications except Benderlink Ethernet Modules with the CB-EL1 current loop board.
Straight Through Pinout
| RJ-45 Side - Female DB9 Side - Female |
| Function | Wire Color |
RJ-45 Pin |
to | DB9 Pin |
Function |
| RTS | Blue | 1 | ---- | 7 | RTS |
| DTR | Orange | 2 | ---- | 4 | DTR (+5v) |
| GND | Black | 3 | ---- | 5 | GND |
| TXD | Red | 4 | ---- | 3 | TXD |
| RXD | Green | 5 | ---- | 2 | RXD |
| DCD | Yellow | 6 | ---- | 1 | DCD |
| DSR | Brown | 7 | ---- | 6 | DSR |
| CTS | Grey | 8 | ---- | 8 | CTS |
Note about the DCD Yellow Wire
The DCD Yellow (RJ45 Pin 6) connection was added on July 4, 2014. It is necessary for a connection to connector cable spec 40 for connection to the MiiC benders. (See Cable Spec 40 - RJ45-DB25 MiiC Pinout)
Note to ATT technicians: Include the DCD Yellow wire in all Cable Spec 1 adapters so that they can work with the MiiC bender serial connection.
Gender
Assume that you should use the DB-9 FEMALE for connection to standard male COM ports.
Label
Label each of these adapters with "ST", which means "Straight Through".
Important Testing Note
| The receiving pins in this adapter are prone to jump out of their inserted holes if they are not properly pressed in. With the plug NOT snapped into the cover, plug the port into a DB9 male port to be sure none of the receiving pins are pressed back out of the inserted holes. |