There is an odd issue with the pre-boot BitLocker PIN: If the SIGNET device is left plugged in during startup, it duplicates x 9 everything that is typed. Please see attached screen print.
As you suspect, it may have something to do with SIGNET not being a boot mode compliant USB keyboard.
As a simple remedy, you may want to advise BitLocker pre-boot PIN users to simply unplug the SIGNET device before turning on the PC.
[Tested on an HP laptop using Windows 7 Enterprise Service Pack 1.]
There is an odd issue with the pre-boot BitLocker PIN: If the SIGNET device is left plugged in during startup, it duplicates x 9 everything that is typed. Please see attached screen print.
As you suspect, it may have something to do with SIGNET not being a boot mode compliant USB keyboard. As a simple remedy, you may want to advise BitLocker pre-boot PIN users to simply unplug the SIGNET device before turning on the PC. [Tested on an HP laptop using Windows 7 Enterprise Service Pack 1.]