Ice Fishing -- "Tip Down"

Do you know of any info. on how to build or purchase a well made "Tip Down" ice fishing system? I see them used occasionally on local lakes and the kids have a lot of fun with them.I actually owned one years ago that had a buzzer alarm built in that would sound when the rod tipped down. Don't remember the make of it though. Any help would be appreciated.

Thanks for all your help,

Greg Adams