| Null Modem |
| From | To |
| 1 | 1 |
| 2 | 3 |
| 3 | 2 |
| 4,5 | 8 |
| 6 | 20 |
| 7 | 7 |
| 20 | 6 |
| 8 | 4,5 |
Null Modem
w/handshake |
| From | To |
| 1 | 1 |
| 2 | 3 |
| 3 | 2 |
| 4 | 5 |
| 5 | 4 |
| 6 | 8,20 |
| 7 | 7 |
| 8,20 | 6 |
| Modem Eliminator |
| From | To |
| 1 | 1 |
| 2 | 3 |
| 3 | 2 |
| 7 | 7 |
| 4,5 | NC |
| 6,8,20 | NC |
Reference:
RS232 Signal
1 - Sig Gnd . . . . . . . . . . Normally Shield or Chassis Ground
2 - TXD . . . . . . . . . . . . . Transmit Data
3 - RXD . . . . . . . . . . . . . Receive Data
4 - RTS . . . . . . . . . . . . . Request to Send
5 - CTS . . . . . . . . . . . . . Clear to Send
6 - DSR . . . . . . . . . . . . . Data Set Ready
7 - GND . . . . . . . . . . . . . SIGNAL Ground
8 - DCD . . . . . . . . . . . . . Data Carrier Detect
20 - DTR . . . . . . . . . . . . Data Terminal Ready
Note: Ring Indicate (RI) is not used or needed in computer-to-computer (DTE to DTE) direct connect configurations.