Abstract: The display (12) comprises a band carrying a series of visual items of information and held taut between two rolls (5, 9) onto which it is rolled, the rolls being parallel to each other and rotatively mounted in a frame (1), and a synchronous driving mechanism (18) for the two rolls. The driving mechanism comprises a toothed belt or chain (21) driven by a motor (19) and cooperating with a first sprocket wheel (22) keyed on the first roll (5) and a second sprocket wheel (23) freely rotatable on the second roll (9) and connected to the latter by elastically yieldable means (25) for compensating for the tension of the band as a function of the variation in the diameter of the roll resulting from the rolling up of the band.

Abstract: A viewing device for X-ray films or the like automatically masks the areas of the viewing screen not in registry with the film to be viewed responsive to the insertion of a film. The device includes a dimension sensing mechanism which aligns a selected mask with a positioned film automatically in accordance with the sensed dimension.

Abstract: A changeable printed alphanumeric display module is disclosed for displaying one character at a time in a viewing window. Each tape of a set of tapes is printed on both front and back surfaces with character segments and is connected between a driving roller and a driven roller in a manner to display one front surface segment and one back surface segment at a time. The tape segments which carry the respective character segments are progressively longer from one end of the tape to the other and the set of tape segments which are displayed together in the window all bear different character segments of the same character so that an entire character is displayed. All tapes in the set are driven in unison to successively present the character segments of each tape in registry with respective window segments.