I labeled these pinouts A and B, but those names are arbitrary. You'll find that layout B is most commonly used in the blue cisco cables... particularly the older cables that had a separate connector. In both cases, the green wire is optional (and is soldered to the red wire, at least in the Cisco version) - at least with all the network gear I've worked with in the last few years. Also, pins 1 and 9 aren't used in either version.
The advantage of these two are that you need only two of these adapters (one of each) and a cat 5 or cat 5e cable.
If you need to connect to a piece of Cisco gear (they typically use the RJ45 serial port,) just use the type A connector and a cat5 cable direct to the Cisco box.
If you need to connect to a piece of gear that uses DB9, place one connector on each end of the cat 5 cable.
|type||Pin 1||Pin 2||Pin 3||Pin 4||Pin 5||Pin 6||Pin 7||Pin 8||Pin 9|