Feature: 1. 1500m Ultra Long Talking Distance: This intercom doorbell adopts professional chip, the theoretical talking distance can be up to 1500m in a flat and open place, which makes your contact more convenient. 2. Wide Signal Coverage: This intercom doorbell uses 462MHz radio frequency, the signal coverage is wider, and it is even easier to penetrate the wall. 3. Clear Sound Quality: This intercom doorbell adopts core noise reduction technology, and the intelligent noise reduction makes your calls clearer. 4. 3 Levels Volume Adjustment: This intercom doorbell features three levels of volume adjustment, with a maximum volume of no less than 112 decibels, which can be heard in the bedroom or in the kitchen. 5. IP44 Waterproof Capability: This intercom doorbell has IP44 waterproof capability, which can be dustproof and waterproof, so you can rest assured that the intercom doorbell can be installed outdoors. Specification: Item Type: Wireless Voice Intercom Doorbell Material: ABS Power: 0.5W Channel: A, B, C 3 Channels Connection Number: Maximum of 3 sets of non serial number, the same channel number under the connection is not limited. Battery: 2 x 2000mAh Rechargeable Lithium Battery, 1 Battery For Each Machine ( Shipped With Built In Battery ). Package List: 1 x Ternal Machine1 x Charging Base1 x Outer Machine1 x Outer Machine Bracket1 x USB Cable1 x Double Sided Adhesive1 x Doorbell Sticker5 x Screw3 x Expansion Tube