Null modem
![A null modem adapter](/Images/godic/202501/30/Null_modem0417.jpg")
![DB-25 null modem wiring diagram](/Images/godic/202501/30/D25_Null_Modem_Wiring0417.png")
![DE-9 null modem wiring diagram](/Images/godic/202501/30/D9_Null_Modem_Wiring0417.png")
![Wiring pinouts for DB-25 (left) and DE-9 (right) connectors](/Images/godic/202501/30/Null_modem_xon-xoff.svg0417.png")
Null modem is a communication method to directly connect two DTEs (computer, terminal, printer, etc.) using an RS-232 serial cable. The name stems from the historical use of RS-232 cables to connect two teleprinter devices to two modems in order to communicate with one another; null modem communication was possible by using a crossed-over RS-232 cable instead to connect the teleprinters directly to one another.