Abstract: Printed publications capable of interacting with the reader require information, particularly page number, detection. One method is to attach a bar code made of reflective and non-reflective materials onto each page to deliver the page number by reflection. This method may be easily affected by several factors, including the direction of the light source, or even being totally blocked by other objects like the hand of a reader. This invention provides an improved printed publication having at least one opening on each page that substantially coincides with the openings in adjacent pages. An information indicator on each of the pages delivers a signal through these openings to indicate the open configuration or the page number.