Use this to distinguish hard or soft required states. E.g a called-for switch <i>should</i> be in the given position whilst a flank protection switch <i>must </i>be in the given position.<br /></p><p>The interlocking normally controls an element into a required position. The enforce-policy expresses what the interlocking must do with the element.<br /></p><p>enforce=must means that the condition is fulfilled only when the element acquires the given status, enforce=should means that this given status is the preferred status but no conditio sine qua non, finally enforce=none means that the interlocking is not given a desired status; in other words the IL can ignore the given status.<br /></p>