Features 1、3 Levels Of Volume Adjustable: The elderly can also hear, the highest volume is not less than 112 decibels, whether in the bedroom or in the kitchen can be heard, built‑in 30 ringtones, a variety of tunes to choose from 2、2000M DISTANCE: Using professional chip, the theoretical call distance can achieve 2000M in flat and open areas, making your contact more convenient. 3、WIDE SIGNAL COVERAGE: Adopting 462MHz radio frequency, the signal coverage is wider and wall crossing is simpler. 4、LONG ENDURANCE: Both the indoor and outdoor units are equipped with 1800mAh rechargeable lithium batteries, ensuring long lasting battery life. 5、ANTI INTERFERENCE: With 16 separate channel options, this wireless doorbell can easily avoid interference in wireless frequency bands. Specification Item Type: Wireless Voice Doorbell Material: ABS Power: 0.5W Channel: 1-16 Number of Connections: Up to 16 sets without serial numbers, unlimited connections under the same channel number Battery: 2 x 1800mAh rechargeable lithium battery, 1 battery per host (shipped with built in battery) Package List 1 x Indoor Unit 1 x Charging Base 1 x Outdoor Unit 1 x Outdoor Unit Bracket 1 x USB Cable 1 x Double Sided Adhesive 1 x Doorbell Sticker 5 x Screw 3 x Anchor