串行直连电缆 25针-25针(NullModem)
串行直连电缆用于两台计算机的直接相连，电缆两头的插头都是 25 针母插头：
|
引脚界说 |
| D-Sub 1 | D-Sub 2 |
|
|---|---|---|---|
|
Receive Data |
3 |
2 |
Transmit Data |
|
Transmit Data |
2 |
3 |
Receive Data |
|
Data Terminal Ready |
20 |
6+8 |
Data Set Ready + Carrier Detect |
|
System Ground |
7 |
7 |
System Ground |
|
Data Set Ready + Carrier Detect |
6+8 |
20 |
Data Terminal Ready |
|
Request to Send |
4 |
5 |
Clear to Send |
|
Clear to Send |
5 |
4 |
Request to Send |
