A cost-saving way to convert a straight through cable into a null modem cable. The ST-NM9FF Null Modem Cable Adapter features two DB9 female connectors. The ST-NM9MF Null Modem Cable Adapter features one DB9 male and one DB9 female connector. The ST-NM9MM Null Modem Adapter features two DB9 male connectors. Lifetime warranty and free lifetime technical support.