Features 1、2000M ULTRA LONG CALL DISTANCE: Using professional chips, in flat and open areas, the theoretical call distance can arrive 2000M, making your contact more convenient. Adopting a 462MHz radio frequency, the signal coverage is wider and wall crossing is simpler. 2、CONTINUOUS SOLAR CHARGING: Solar energy is continuously charged, and when fully charged, the external unit is used 3 to 5 times a day, with a range of about 12 months. Both the internal and external units are equipped with 1800mAh rechargeable lithium batteries, ensuring long lasting battery life. 3、ANTI INTERFERENCE: With 16 separate channel options, it can easily avoid interference in wireless frequency bands. 4、3 LEVEL VOLUME ADJUSTMENT: Elderly people can also hear it, with a maximum volume of no less than 112 decibels. The doorbell can be heard in both the bedroom and kitchen, with 30 built in ringtones and multiple tunes to choose from. 5、MULTIPLE SCENES FOR USE: This doorbell is suitable for homes, villas, companies, teahouses, offices, homestays, and other areas. 6、DUSTPROOF WATERPROOF: IP44 waterproof capacity, no dripping, you can be installed the external unit outdoors with confidence. Specification Item Type: Wireless Intercom Doorbell Material: ABS Power: 0.5W Channel: 1 to 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 (shipped with built in battery) Package List 1 x Internal Unit 1 x Charging Base 1 x External Unit 1 x External Machine Bracket 1 x USB Cable 1 x Double Sided Adhesive 1 x Door Bell Sticker 5 x Screw 3 x Expansion Tube