An adapter is a hardware device or software component that converts transmitted data from one presentation form to another. The data presentation can be, for example, a message sent between objects in an application or a packet sent through a network. A null modem adapter enables users to transform a normal serial cable into a null modem. It contains the necessary crosslinks between the signals. A null modem adapter converts any straight-through wired cable with connectors into a null modem "cross-wired" configuration. This configuration is suitable for many serial PC to PC and PC to printer applications.

25 pin female connector
25 pin male connector
Null Modem Adapter Pinout
|
Signal |
Female |
Male |
|
|---|---|---|---|
|
Shield Ground |
1 |
1 |
Shield Ground |
|
Transmit Data |
2 |
3 |
Receive Data |
|
Receive Data |
3 |
2 |
Transmit Data |
|
Request to Send |
4 |
5 |
Clear to Send |
|
Clear to Send |
5 |
4 |
Request to Send |
|
Data Set Ready |
6 |
20 |
Data Terminal Ready |
|
Data Terminal Ready |
20 |
6 |
Data Set Ready |
|
Ground |
7 |
7 |
Ground |
The team at The Hardware Book contributed this data.


