Wire the normally open contact of the switch to the 1 Hz time base. Wire the output from pin 8 of the fourth 7490 to the normally closed contact of a single pole double throw switch. Provide the ability to set the hours section of the counter.This 7490 is the tens of minutes counter. Wire pin 11 of the third 7490 as the clocking input of the fourth 7490.Wire the wiper of the switch to the clock input of the third 7490. Wire the output from pin 8 of the second 7490 to the normally closed contact of a single pole double throw switch.
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