Feature: 1. 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. 2. MULTIPLE RINGTONES: The receiver adopts a doorbell design, with 22 different ringtones for individual preference, and 8 doorbells for retail business use. 3. 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. 4. MULTIPLE FUNCTIONS: Motion activated sensor ringtone, door alarm, email alert, and added silent strong vibration reminder, which is suitable for private or quiet places. 5. 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