這個串口線把一個25 針的串行口接到9 針的串行口上，PC 一端為9針的母插頭：
連接到串行設備為25 針的公插頭：
|
25針轉9針串口線信號定義 |
|
|
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 |