RS-232 の信号とピン配置
| ピン番号 | 信号名 | 方向 | |||
| Dsub25P | Dsub9P | EIA | ITU-T (V.24, V.28) | JIS (X5101) | DTE<->DCE |
| 1 | NA | AA | FG (Frame Ground) | PG (FG) | - |
| 2 | 3 | BA | SD (Send Data) | TxD | -> |
| 3 | 2 | BB | RD (Receive Data) | RxD | <- |
| 4 | 7 | CA | RS (Request to Send) | RTS | -> |
| 5 | 8 | CB | CS (Clear to Send) | CTS | <- |
| 6 | 6 | CC | DR (Data Set Ready) | DSR | <- |
| 7 | 5 | AB | SG (Signal Ground) | SG | - |
| 8 | 1 | CF | CD (Carrier Detect) | DCD | <- |
| 9 | NA | +Voltage | <- | ||
| 10 | NA | -Voltage | <- | ||
| 11 | NA | Unassigned | - | ||
| 12 | NA | Carrier Detect 2 | <- | ||
| 13 | NA | Clear to Send 2 | <- | ||
| 14 | NA | Send Data 2 | -> | ||
| 15 | NA | DCE Trancemitter Timing | <- | ||
| 16 | NA | Receive Data 2 | <- | ||
| 17 | NA | Receiver Timing | <- | ||
| 18 | NA | Local Loopback | -> | ||
| 19 | NA | Request to Send 2 | -> | ||
| 20 | 4 | CD | ER (Equipment Ready) | DTR | -> |
| 21 | NA | Signal Quality Detector | <-> | ||
| 22 | 9 | CE | CI (Calling Indicator) | RI | <- |
| 23 | NA | Data Signal Rate Selector | <-> | ||
| 24 | NA | DTE Transmitter Timing | -> | ||
| 25 | NA | Test Mode | <- | ||
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