Some time ago, I was stumbling through eBay and accidentally bought 10 buzzers from a quiz show for just a buck, being the only bidder. I am not quite sure which quiz show the buzzers are from, but they were sold from a TV-production-company and labeled with arrows.
Technically, when a buzzer is pressed, two pins are connected electrically. I was looking for a cheap and easy way to connect the buzzers to my computer. So I ended up buying a bunch of cheap USB-keyboards, forcing them open and taking their USB-controller. Never having seen this before, a keyboard-controller is very simple: there are several contacts and pressing a key connects two of them. Each key has an own combination of two contacts. I decided to solder the buzzer to the num-pad-keys, so buzzer #1 literally types "1", buzzer #2 types "2" and so on...
As having connected multiple keyboards to a computer isn't much of a problem each buzzer has it's own USB-controller. I wrote a little Processing-application interpreting the keyboard-input and displaying a different color for each buzzer. Of course it play the well-known buzzer-sound, too. After a buzzer is triggered, the application is locked and you need to press the spacebar to rearm.
The code and binaries of Mac OS, Windows and Linux can be found in the corresponding github-repo. Happy quizzing!