串行直连电缆用于两台台电脑通过串行口直接相连，电缆两端的插头都是9 针的母插头：
通过此表可以看出两台电脑通过串口直接连接传输数据的接线方法：
| | D-Sub 1 | D-Sub 2 | |
| Receive Data | 2 | 3 | Transmit Data |
| Transmit Data | 3 | 2 | Receive Data |
| Data Terminal Ready | 4 | 6+1 | Data Set Ready + Carrier Detect |
| System Ground | 5 | 5 | System Ground |
| Data Set Ready + Carrier Detect | 6+1 | 4 | Data Terminal Ready |
| Request to Send | 7 | 8 | Clear to Send |
| Clear to Send | 8 | 7 | Request to Send |
