Putty+into+Fortinet

Console cable is an RJ45-DB9 type. If you don’t have DB9 serial port on your computer, you could search for a USB-DB9 mail converter. About the software, I personally choose to use Putty to connect to Fortigate. Putty could establish connection to devices support serial console. Fortigate supports console connector ranges from DB9 to RJ45. Fortigate console settings are: Have these settings configured in Putty. Serial line, select COM1. Speed, type in 9600. 
 * Baud Rate (bps): 9600
 * Data bits: 8
 * Parity: None
 * Stop bits: 1
 * Flow Control: None

To double check the serial connection settings, select Serial on the left panel 
 * Click Open to make connection
 * And hit Enter on your keyboard once or twice.
 * The login screen should appear
 * Login with your admin username and password.