To connect a DB-9 equipped asynchronous adapter to a modem, use a standard "straight-through" cable. A straight-through cable has a DB-9 female connector at the Digi end, and a DB-9 male connector at the modem end. All 9 pins are connected, 1 to 1, 2 to 2, 3 to 3, etc. Use shielded cable, and connect pin 1 of each connector to the cable shield.