Some Vault models have an external COM port that can be used as a serial console connection to view the Vault’s output. This output is simply a redirection of the Vault’s VGA or HDMI port (depending on the model you have). This can be useful in the event that you need to access the Vault’s output, but don’t have a monitor handy, or for more permanent remote adminitration uses.
The COM port defaults to 115200, which can be changed in the Vault’s BIOS.
More information on how to use the Vaults’s Serial COM port can be found here: http://protectli.com/kb/com-port-tutorial/