串行直連電纜 9針-25針(NullModem)
串行直連電纜用于兩臺計算機的直接相連，電纜兩端的插頭一頭是 9 針母插頭，另一頭是 25 針母插頭：
|
引腳定義 |
|
|
D-Sub 9 |
D-Sub 25 |
|
|---|---|---|---|
|
Receive Data |
2 |
2 |
Transmit Data |
|
Transmit Data |
3 |
3 |
Receive Data |
|
4 |
6+8 |
Data Set Ready + Carrier Detect | |
|
System Ground |
5 |
7 |
System Ground |
|
Data Set Ready + Carrier Detect |
6+1 |
20 |
Data Terminal Ready |
|
Request to Send |
7 |
5 |
Clear to Send |
|
Clear to Send |
8 |
4 |
Request to Send |