What is a null modem cable?
A NULL modem cable allows two PCs to communicate, or in our case allows two serial ports on the same machine to be connected and transcieve data. The transmit and receive pins are crossed across the connector (pin 2 connects to pin 3, and pin 3 to pin 2), in contrast to a straight through cable, where pin 2 is connected to pin 2 and pin 3 is connected to pin 3.