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 Receiver 1 x Infrared Detector 1 x Bracket 1 x User Manual 2 x Screws 2 x Plastic Plugs 1 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