The RBT-402 has a standard BIOS. Hit the DEL key on power-up to enter the setup screens.
The BIOS Screen identifies itself as Phoenix - AwardBIOS
The Boot options are:
Although it doesn't appear in the list above the unit does try to boot from the network first of all.
My first attempts to boot from USB failed - I kept on getting complaints about NO OPERATING SYSTEM thanks to the erased flash. After fiddling around a bit I was successful. I haven't investigated things fully to work out exactly what's required but this is what I ended up doing.
NB If you have no USB pen drive plugged in (as was the case when I first entered this screen) you'll only see the entry for the flash memory on the IDE interface.1. Ch0 MJ. : InnoDisk Corp. - EDC40
2. USB-HDD0 : Generic Flash Disk
The RBT-472v had a default BIOS password set. This turned out to be 10ZIG.
'Grep'ing the dmesg output for 'BIOS' showed me that the RBT-402 BIOS was dated 09/17/2008 whilst that of the RBT-472v was dated 07/09/2009.
As noted earlier my RBT-402 came with an erased flash. From the 10ZiG website:
As far as I can see there is no firmware download available from the 10ZiG website. If you want the original firmware I guess you need to get in touch with them and ask for it.
The Clientron website does have a FTP Download page but you need a user ID and password in order to find out what is there. I guess it's another case of getting in touch with them to get some logon credentials.