Abstract: A printing machine having an operator removable housing comprising a photoconductive member with a web entrained about a portion thereof. A latent image is recorded on the photoconductive member and marking particles transported to the portion of the web entrained about the photoconductive member. In this way, the latent image recorded on the photoconductive member attracts the marking particles to the web in image configuration. A copy sheet is advanced into contact with the marking particles on the web. The marking particles interposed between the web and the copy sheet are heated. After cooling, the copy sheet is separated from the web with the marking particles remaining affixed thereto.

Abstract: Permanent, meaningful information is so associated with removable, confusing information, at least some of which is usually similar in character to said permanent, meaningful information, as to make it effectively impossible for an observer to discriminate between the two types of information even though both types of information in the association may be legible. Such a system is advantageously used in instructional systems and particularly in responsive answer formats.