Int 21 Fn 253A  P - Phar Lap 386/dos-extender V3.0+ - Install Mod. Seg Fa  [E]

   AX = 253Ah
   ES:EBX -> function to be called when INT 21/AH=4Ah is about to return
       an error

Return: CF clear
   ES:EBX -> previous handler

See Also: AH=4Ah