If the system is functioning properly, messages including POST/BIOS should output to the console port.
The BIOS itself is password-protected, but can be accessed via the console port.
Regardless, this unit has likely had a hardware failure.
Having said that, everything you can recover is on the drive itself, and if you can access that...it's a step in the right direction.
Of course, it depends on whether this is a gateway that was externally managed or was standalone (included local management) as to how recoverable the security policy configuration will be.