A digital display revolution counter.
David A. Brodie, R. S. Bhogal, E. Mitchell · British Journal of Sports Medicine · 1981
The pulse is fed to pin 14 of the 7490 IC decade *LED is Light Emitting Diode.counter.The display is driven by a 7447 IC BCD-to-* IC BCD is Integrated Circuit Binary Coded Decimal seven-segment decoder-driver.