Port Pinout
| 9 pin # | 25 pin# | Acronym | Full name | Direction | Purpose |
| 1 | 8 | DCD | Data Carrier Detect | Into PC | Modem connected to another |
| 2 | 3 | RxD | Receive Data | Into PC | Receives bytes into PC |
| 3 | 2 | TxD | Transmit Data | Out of PC | Transmits bytes out of PC |
| 4 | 20 | DTR | Data Terminal Ready | Out of PC | I'm ready to communicate |
| 5 | 7 | SG | Signal Ground | ground | ground |
| 6 | 6 | DSR | Data Set Ready | Into PC | I'm ready to communicate |
| 7 | 4 | RTS | Request To Send | Out of PC | RTS/CTS flow control |
| 8 | 5 | CTS | Clear To Send | Into PC | RTS/CTS flow control |
| 9 | 22 | RI | Ring Indicator | Into PC | Telephone line ringing |