The Philip Harris Foundation Physics - Light Gate includes a battery operated timer, two light gates with cords, 9V battery, a backup AC adaptor, and a user manual. perfect for experiments on the go. The light gates come with convenient thumbscrews, making them easy to connect and reposition.  

• Standard Stopwatch Mode: records time from start to stop
• Interval Mode: measures the duration of an interruption 
• Frequency Mode:  tracks the rate of regular interruptions
• Period Mode: calculates the time between the first and third interruptions
• Count Mode: records the number of times the photogate beam is broken and it also functions as a 
• Dimensions: 15 x 15 x 6 cm.