I hope the below article is of some help to teams in deciding what to buy. If you know of additional systems, please let me know. I suggest calling or writing them for buzzer info. They also have larger systems and are suitable for television. It is very light weight.
Cost is approx.
Expands indefinitely to allow as Many players as needed. One year manufacturer's warranty on defects in material and workmanship, assuming normal use. Moderators panel has small lights which show which team rang in. Players have a box connected by cable to moderators box. Each player has a small light bulb on his box which locks out other players once you press the button to ring in.