The perfect way to monitor the time students spend on trips outside your classroom or learning center. You can set each for an allotted time and use the monitor’s memory function to double-check how long each of the past three users had the pass. The pass with accompanying lanyard and monitor unites feature clear time readouts and “time’s up” warning lights and alarms. You can set each for an allotted time and use the monitor's memory function to double-check how long each of the past three users had the pass. Operates on four "AAA" batteries (two each for pass and monitor units). One-year warranty.