Feature: 1. The perfect combination of doorbell and walkie-talkie, supporting multiple walkie-talkies or doorbells simultaneously online. 2. You can know the visitors anytime, anywhere, and the distance is up to 3.1mile (5 kilometers). 3. Easy to install, it can be installed in a few minutes with our screw package. 4. Outdoor doorbell, defensive shell, waterproof, anti-exposure, anti-dust. 5. Rechargeable lithium battery, automatic sleep design, low power consumption, long life, 3 hours of charging, 60 days of use. 6. The doorbell that integrates receiving and transmitting has strong penetrating power and signal transmission is not affected. 7. Can be used as a caller for the elderly and pregnant women. 8. Can be applied to a variety of occasions such as home, hotel, KTV. Specification: Condition: 100% Brand New Item Type: Intercom Doorbell Color: Shown as Picture Frequency Range: 470.00-480.00mhz Rated Voltage: DC3.7V Rechargeable Lithium Battery(Included) Antenna Impedance: 50 Ohms Working Mode: Same Frequency Simplex or Different Frequency Simplex Output Power: ≤5W Maximum Frequency Offset (Wideband, Narrowband) <5k/2.5khz Clutter Radiation: <7μW Emission Current: ≤2.8A Lithium Battery: 1800mah(Included) Ctcss/dcs (wideband, Narrowband): 0.75khz±50hz, 0.37khz±30hz Modulation Sensitivity: ≤12mA Modulation Distortion: ≤5% Reference Sensitivity: -122dbm (12db Sinad) Audio Power: 1W Effective Distance: Approx. 5 kilometers/3.1mile. Package List: 1 x Doorbell (Built-in DC3.7V Lithium Battery)2 x Walkie-talkie (Built-in DC3.7V Lithium Battery)1 x Power Supply1 x USB Data Cable1 x Mounting Screw Package2 x Lanyard1 x Instruction Manual