Multiple base counting display for mathematics teaching - allows number sequence and indexing function to be altered for different time bases

摘要

The display allows arithmetic numbers to be visualised in relation to different counting bases. It has a series of mobile elements (3;3a,3b) each corresponding to a given number order and marked with figures corresponding to the selected counting base. The mobile elements (3,3a,3b) are separated from one another via fixed screens (4) cooperating with movable screen (5) to obtain a variable viewing window selected in dependence on the counting base. A ratchet device (9) is provided between adjacent elements (3a,3b) for indexing the higher order element (3b) via the lower order element (3a) by an amount corresponding to the aperture of the viewing window. Pref. the mobile elements (3,3a,3b) comprise coaxial rotary drums each adjacent pair separated from one another by a fixed screen (4) and a movable screen (5). An interchangeable band carrying the numbers in a specific counting base sequence is attached around the periphery of each drum (3,3a,3b).