this pdf tells you how to do a fastest switch circuit. give connection as per the circuit diagram and observe the output.

1. FASTEST SWITCH CIRCUIT
SUBMITTED BY:
MANIKANDAN.N
(M.TECH COMMUNICATION SYSTEMS)
REG NO: 118102013

2. CIRCUIT DIAGRAM:
PRINCIPLE:
Four press to ON type of switches are placed at the input of the IC 7475
which is a 4-Bit Bistable Latch with Complementary Outputs.
The button which is pressed first, triggers the relevant output of the IC
7475, which in turn prompts the IC 7420 to instantly deactivate the
other inputs from the other push buttons, rendering the whole system
inactive, except the one which had the first trigger through the push
button.This output concerning the triggered latch illuminates the
relevant LED, indicating the button number which was pressed first.
APPLICATION:
This circuit can be used in the quiz programs.
Used to find the which contestant has pressed the switch first.