这个串口线把一个25 针的串行口接到9 针的串行口上，PC 一端为9针的母插头：
连接到串行设备为25 针的公插头：
|
25针转9针串口线信号定义 |
|
|
9-Pin |
25-Pin |
|---|---|---|
|
Carrier Detect |
1 |
8 |
|
Receive Data |
2 |
3 |
|
Transmit Data |
3 |
2 |
|
Data Terminal Ready |
4 |
20 |
|
System Ground |
5 |
7 |
|
Data Set Ready |
6 |
6 |
|
Request to Send |
7 |
4 |
|
Clear to Send |
8 |
5 |
|
Ring Indicator |
9 |
22 |