Feature:1. [Wireless Intercom System] This intercom doorbell kit includes one outdoor unit and two indoor units, allowing for intercom communication. The indoor units can also communicate with each other.2. [Multi Functional] With 15 selectable ringtone options and three adjustable volume levels, you can choose the perfect ringtone and volume to suit your preferences and needs.3. [Extended Transmission Range] The wireless transmission distance can achieve up to 200 meters in an open area, and 5 to 50 meters with obstacles, ensuring reliable communication.4. [Expandable Intercom System] This intercom doorbell system is expandable, allowing you to add additional indoor or outdoor units to your system, compatible with almost any indoor or outdoor installation.5. [Intelligent Power Saving] Equipped with intelligent power saving chip, this 2 way voice doorbell offers exceptional battery life. After a full charge, it can be used for over six months under normal usage.Specification:Item Type: Intercom Doorbell SystemMaterial: ABSOutdoor Doorbell Power Supply Method: 3 x AA Batteries (Not Included)Indoor Doorbell Power Supply Method: 1 x BL 4C 890mAh Lithium Ion Battery (Built In)Indoor Doorbell Charging Voltage: DC 5VWorking Temperature: -20 to +55Wireless Distance: 200M for Outdoor Doorbell (Unobstructed), 5-50M for Indoor Doorbell (Obstructed)Wireless Frequency: 410M-490MHz.Package List:1 x Outdoor Doorbell2 x Indoor Doorbell3 x Double Sided Adhesive Tape2 x Base2 x Charging Cable1 x Screwdriver1 x Instructions