{description of positioner}
{best known value of positioner - need [n] as may be scanned}
{raw value of positioner - need [n] as may be scanned}
{targeted (commanded) value of positioner - need [n] as may be scanned}
{maximum allowable difference between target_value and value}
{minimum allowed limit to set value}
{maximum allowed limit to set value}
{Hardware device record, e.g. EPICS process variable, taco/tango ...}