Int 21 Fn 3F  - Trusted Access - Nb.sys - Get State                        [y]

   AH = 3Fh
   BX = file handle for device "$$NB$$NB"
   CX = 0002h (size of state)
   DS:DX -> buffer for state record

Return: CF clear if successful
       AX = number of bytes actually read (0 if at EOF before call)
   CF set on error
       AX = error code (05h,06h) (see AH=59h)
Program: Trusted Access is a security and access-control package by Lassen
     Software, Inc.; NB.SYS is a device driver to prevent the user from
     terminating CONFIG.SYS or AUTOEXEC.BAT with Ctrl-Break

See Also: AH=40h"NB.SYS",AX=4101h

Format of state record:
Offset Size    Description
 00h   BYTE    00h off, 01h on
 01h   BYTE    keys being disabled
       bit 0: Ctrl-Break
       bit 1: SysRq
       bit 2: Ctrl and Alt
       bit 3: Ctrl-Alt-Del
       bit 7: all keys (overrides other bits)