With gap between light guide elements (includes open light path preset):
(under subclass 900) Art collection of liquid level sensors related to those in ... in which a light guide which transmits light from a light source to a detector has a gap which light from the source traverses, or does not traverse, depending on the angle of the end faces of the light conductor, whether or not the liquid is in the gap, etc. The designation "open light circuit present" means that light from the light source normally is not transmitted from one
light conductor end face across a gap to the other light conductor end face when the gap is not filled with liquid. The designation "closed light circuit preset" means that light from the light source is normally transmitted across the gap between the light conductor end faces when liquid is not filling the gap. Illustrations of open and closed light circuits appear below: [figure]
