Roule&Acirc; RL-3978C Driveway Entryways Home and Office Alarm Motion Sensor -500 Feet Long Range Wireless, 16 Alarm Tones Selections, Home Security Alert Alarm System Kit Multi-channel warning: free combination, each channel can learn the codes up to 20 infrared sensors. Warning tones: There are 16 different tone selections, the unit will emit warning tone when an infrared sensor is triggered. Learn codes: one million sets of learning codes can effectively avoid interference. Indicator light: after been triggered, the corresponding indicator will flicker for about 30 seconds, all three channel lights will blink when battery runs low. IP44 waterproof and dust-proof sensor, infrared sensing distance: 21 feet.