Quiz Timer

EE JULY/AUGUST 1988 Here is a simple "who"s the first" circuit that can be used in quiz games with up to eight participants or groups of par- ticipants. The circuit indicates the first one to press his key by a glowing LED against his number or any other identifi- cation used in the quiz or game. At the same time, the circuit gives an audible indication that some key has been pressed. The RESET key enables the quiz master to restore the circuit"s original state before updating the score and pro- ceeding with the next question or assignment. After RESET has been pressed, the eight R-S bistables in ICI and IC2 are reset. TheQoutputsallgologiclowand, consequently, the output of 1C3 goes logic high. The circuit is now ready to be operated. For example, if Si is pressed first, the first bistable is set and output Q1 goes high. The output of 1C3 pulls the common line of keys Si... S8 incl. logic low to prevent more bistables being set. Hence, Ql is the only output that is logic high. Th...