Features MOTION SENSOR: Wireless welcome doorbell alarm, using sensor to detect motion and send signals to the receiver, with the option of selecting at least one transmitter. MULTIPLE RINGTONES: The receiver adopts a doorbell design, with 22 different ringtones for individual preference, and 8 doorbells for retail business use. WIRELESS DISTANCE: This wireless doorbell can be transmitted from a long distance, with an open space of up to 280 meters, suitable for larger locations or higher floors. MULTIPLE FUNCTIONS: Motion activated sensor ringtone, door alarm, email alert, and added silent strong vibration reminder, which is suitable for private or quiet places. APPLICABLE PLACES: This motion sensor doorbell is suitable for shopping malls, office spaces, factories, hotels, high end clubs, homes, villas, etc., simple and practical. Specification: Item Type: Wireless Doorbell Model: KS SF20R Receiver Battery: 3 x 3V AA alkaline battery (not included) Infrared Detector Battery: 3 x 3V AAA alkaline battery (not included) Power Supply: 5V Micro USB Volume: 80-96dB Power Supply Transmission Reception Frequency: 433.92MHz Wireless Distance: About 280m / 918.6ft in the open air Environment Temperature: Receiving Host: -10-60℃; Infrared Detector: -10-33℃ Environment Humidity: <80%RH Storage Temperature: -20-70℃ Package List:1 x Receiver1 x Infrared Detector1 x Bracket1 x User Manual2 x Screws2 x Plastic Plugs1 x Double Sided Tape Package List 1 x Receiver 1 x Infrared Detector 1 x Bracket 1 x User Manual 2 x Screws 2 x Plastic Plugs 1 x Double Sided Tape