Feature: 1. Two Way Voice Doorbell: The perfect combination of dual indoor and outdoor intercom allows you to communicate with visitors outside the door. Allows you to identify visitors outside the door based on sound 2. Easy to Use: The doorbell adopts one button call. Hold down the talk button and speak, release to stop. Click call button, the other voice caller rings. 3. Loud Volume: The speaker is loud and adjustable, and the sound is clear. Outdoor open free line communication distance is 500 to 1000 meters. 4. Long Standby Time: The doorbell is built in 1800 mah polymer lithium battery, In general, they work for 30 seconds five times a day for about a week. 5. Automatic Charging Stand: The doorbell is placed on the charging stand when it is in standby mode. The intelligent automatic charging takes about five hours and the power is never off. Specification: Item Type: Wireless Intercom DoorbellMaterial: Abs Battery Type: Polymer Lithium Battery Battery Model: 103450 Battery Capacity: 1800 Mah Power Supply: Polymer Lithium Battery (Delivered with Built-In Battery) Battery Powered: Dc5v/1a Operating Temperature: -20 Degrees Celsius~ 55 Degrees CelsiusTransmission Distance: About 1000 Meters Open, 20-100 Meters Partition Wall, Floor 1 ~ 8 Floor Operating Frequency: B Gear Frequency 462mhz a Gear Frequency 434mhz Working Time: Charge for About 1 Week Charge Time: About 5 Hours Full Music Ringtone: 38 Ringtones Ring Volume: 3 Levels of Adjustment (To Adjust the Volume of the Machine) Call Sound: Level 3 Adjust Call Level (Adjust Volume Button When Talking). Package List: 2 x Wireless Intercom Doorbell2 x Charging Stand 2 x Charging Cable 1 x Instruction Manual