| Pin Number | Signal Name | Description |
|---|---|---|
| 1 | CD (Carrier Detect) | Indicates that a connection to a modem is established(In). |
| 2 | RxD (Receive Data) | Receive data from the transmitting device(In). |
| 3 | TxD (Transmit Data) | Transmit data to the receiving device(Out). |
| 4 | DTR (Data Terminal Ready) | Indicates that the terminal or computer is ready to establish a connection(Out). |
| 5 | GND (Ground) | Ground reference voltage(-). |
| 6 | DSR (Data Set Ready) | Indicates that the modem or peripheral device is ready to establish a connection(In). |
| 7 | RTS (Request to Send) | Indicates the readiness to send data(Out). |
| 8 | CTS (Clear to Send) | Indicates that the receiving device is ready to accept data(In). |
| 9 | RI (Ring Indicator) | Indicates an incoming ring signal from a modem(In). |