Feature 1Remote Operation: This intercom can be used at a long distance of about 1500 meters, without network, without wiring, turn on and use. 2Various Functions: The intercom has internal waterproof design, equipped with large capacity battery, with 2 charging methods. 3Indicator Light: This doorbell has a good feel of the keys, with intercom light and power light display, the user can see at a glance. 4Large 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. 5Multiple Modes: With two indoor units, you can switch between ringing call mode and intercom mode, when the intercom is used.SpecificationItem Type: Wireless Intercom DoorbellMaterial: ABSBattery: Inner Rechargeable Lithium Battery: 3.7V 2000mAh (with built in battery)External Rechargeable Lithium Battery: 3.7V 2000mAh (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 .wang-edit-text{ font-family:'Arial' !important; } .wang-edit-text table { border-top: 1px solid #000; border-left: 1px solid #000; } .wang-edit-text table td, .wang-edit-text table th { border-bottom: 1px solid #000; border-right: 1px solid #000; padding: 3px 5px; } .wang-edit-text table th { text-align: center; }Package List2 x Inner Doorbell1 x Outer Doorbell2 x Charger2 x USB Cable1 x Power Cable1 x Screwdriver1 x Instruction