The concept of how much time is left, is difficult to grasp, especially for our special education students. These unique timers provide a clear visual display of the time remaining. Set to any time between 1-60 minutes, time is up when the red shield is no longer visible. Timers run silently but now have the option of a single auditory cue to indicate the end of that session. You can set the auditory responce mode or not, depending on need. Sorry, no auditory feature available on the wall model. Easy to read dials; battery operated (1 AA-not included). The small personal timers are great for keeping individual students motivated, so you may need more than one.