Abstract: A mechanism for opening a publication and for sensing the open or closed condition of the publication includes an opening mechanism for opening the publication into two sections, a first detector assembly for sensing the presence of one of the sections at a first location, and a second detector assembly for sensing the presence of the remaining section at a second location spaced from the first. An indicator responds to the first and second detector assemblies for indicating that the opening mechanism properly opened the publication when the sections are sensed at both the first and second locations, and for indicating that the opening mechanism missed opening the publication when the sections are sensed at only one of the first and second predetermined locations. Preferably, a piece of reflective tape is positioned at the first and second locations, and each detector assembly emits light that is directed onto the corresponding tape along a predetermined line that is angled 15.degree.-45.degree.