Feature: 1. 2000M Long Range: Using professional chips, in flat and open areas, the call distance can get to 2000M, making your contact more convenient. 2. Stable Signal: 462MHz radio frequency, the signal coverage is wider and wall penetration is simpler. With 16 separate channel options, it can easily avoid interference in wireless frequency bands, anti interference. 3. Durable Battery Life: The built in 1800mAh rechargeable lithium battery ensures long lasting battery life without any issues. 4. Volume Adjustment: Elderly people can also hear it, with a maximum volume of no less than 112 dB, which can be heard in both the bedroom and kitchen. There are 30pcs built in melody and multiple tunes to choose from. 5. Ideal for Outdoor: IP44 waterproof, dust proof, and unobstructed in wind and rain, can be installed outdoors with confidence. 6. Easier Communication: Internal phones can communicate with each other, fast and convenient, smooth communication, wide signal coverage, and easier wall crossing. Specification: Item Type: 2 Way Voice Intercom Doorbell Power: 0.5W Channel: 1-16 Channels Connections: Up to 16 sets without serial numbers, unlimited connections under the same channel number. Battery: 1 x 1800mAh rechargeable lithium battery, shipped with built in battery. . Package List: 1 x 2 Way Voice Intercom Doorbell1 x USB Cable1 x Charging Base