Timetable time display forelaspsed instruction period - using disc covered in stages by sector shaped vanes and with acoustic signal

摘要

The timetable time display is used to indicate the elapsed time of an instructional period, and is driven by pulses supplied from a central control clock. A display disc representing the instructional period is covered in stages by a number of sector shaped vanes, so that the amount of the disc which is visible represents the remaining instruction time. The central clock may supply control pulses to several such displays and an acoustic signal may be provided at the beginning and end of each instructional period.