Fastest Finger First project
The unit can be built in multiples of 2 users up to 8 users on a single PCB. Additional PCBs can be daisy-chained on to allow 10 to 16, 18 to 24 users etc. The is no design limit, though in practice signal degredation will kick in at some stage.
After a couple of iterations, the following was arrived at. It is really very noise-insensitive - you can use long lines between the buttons and the control box. it runs off 12V DC @ 100mA using only cheap CMOS chips. What`s more, it can be scaled do visit page.