2-in-1 classroom timer and noise controller. Times tests, games, any classroom event Too loud? HourGlass lets them know. Visible and audible for the entire classroomHourGlass is a dual-function classroom management system that can be used as a Timer and as a Noise Detector. The giant display of lights is a dynamic measuring tool that can be seen by everyone in a classroom or even an auditorium.One year unconditional warranty. Requires 4 " C" batteries (NOT INCLUDED) or optional AC adaptor. Battery life in a typical classroom operation is 6 months- 2 years, but varies according to usage. 15" x 8" x 4.5" .TIMER MODE adds structure and focus to tests, games and other timed events. Everyone can see the lights fall from the upper part of the " sand timer" to the lower part. As " time's up" approaches the lights turn red, and a one-minute warning tone sounds. When the time is up, sound plays and lights flash to clearly signal the end.NOISE MODE helps control classroom noise. Everyone can see the rows of " sound meter" lights rise and fall, indicating the noise level in the room. At the " trigger point" set by the teacher, a warning sound plays and lights flash, signaling the room to quiet down.