Correction: The buzzer system is to the EAST of spawn— NOT the west.

The buzzer system is now complete.
When one pressure plate is activated, the others are locked out. They remain locked until the reset button is pressed. I built this circuit as a simulation of a real circuit I'll be building in class. I don't know if there will be any practical in-game use of it. There are better Minecraft-only ways of accomplishing the same goal.