This Bright Tech Power Roller Display sometimes jams when changing displays.
But I've been trying to find the fault and for the last few hours its worked correctly, its just old.
You are looking inside the display, motor main cog, both rollers, the clutch and the bar code reader.
When it goes wrong blind slips don't lock, controller shows faulty mechanism and display blanks out.
Music By :- Gunnar Olsen - Trancer and Fly High