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. visit page.
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.