The CLEAR_INTERLOCKED function assigns the value  FALSE  to  the
  parameter   and  returns  the  original  Boolean  value  of  the
  parameter.

  Syntax:

     CLEAR_INTERLOCKED( b )

  The variable 'b' must  be  a  variable  of  type  Boolean.   The
  variable  does  not  have  to be aligned; therefore, it can be a
  field of a packed record.