Linux Networking/Serial NULL Modem cable

Serial NULL Modem cable
Not all NULL modem cables are alike. Many null modem cables do little more than trick your computer into thinking all the appropriate signals are present and swap transmit and receive data. This is ok but means that you must use software flow control (XON/XOFF) which is less efficient than hardware flow control. The following cable provides the best possible signalling between machines and allows you to use hardware (RTS/CTS) flow control.

Pin Name Pin               Pin Tx Data 2 - 3 Rx Data 3 - 2 RTS   4 - 5 CTS   5 - 4 Ground  7 - 7 DTR   20 -\--- 8 DSR   6 -/ RLSD/DCD 8 ---/- 20 \- 6