Only one LED is turned on when S1 and S2 are pressed. The LED that will be on is just the correspondent to the switch that is activated first. This circuit can be used in contests or competitions. Sensors, such as reed switches, can be used to replace the switches. The RST switch is used to reset the circuit after a contest. The circuit is shown in Figure bellow. If lamps are to be used in the application, a drive stage can be used. See the site for suggestions. The basic configuration can be extended to include more than two switches.