Feature 1 Remote Operation: This intercom can be used at a long distance of about 1500 meters, without network, without wiring, turn on and use. 2 Various Functions: The intercom has internal waterproof design, equipped with large capacity battery, with 2 charging methods. 3 Indicator Light: This doorbell has a good feel of the keys, with intercom light and power light display, the user can see at a glance. 4 Large Battery Capacity: The doorbell adopts intelligent power saving chip, which can be used for more than half a year under normal circumstances after a full charge. 5 Multiple Modes: With two indoor units, you can switch between ringing call mode and intercom mode, when the intercom is used.Item Type: Wireless Intercom DoorbellMaterial: ABSBattery: Inner Rechargeable Lithium Battery: 3.7V 1800mAh (with built in battery)External Rechargeable Lithium Battery: 3.7V 1800mAh (with built in battery)Use: Widely used in home, office, laboratory environment, etc., medicalWorking Temperature: -20-55Transmission Distance: 1000m in the open, 20-50m across the wallOperating Frequency: 410M-490M Package List2 x Inner Doorbell1 x Outer Doorbell2 x Charger2 x USB Cable1 x Power Cable1 x Screwdriver1 x Instruction