General description Introducing the Pack Voice Intercom Doorbell, a smart wireless call doorbell designed for both home and office use. This new model features long-distance communication capabilities, loud sound, and clear intercom functionality. The pack includes three doorbell system units that can easily switch between ring calls and intercom mode. With a transmission distance of up to 1000m in open areas and 20-50m through walls, this intercom is highly convenient. Each unit is equipped with an intercom indicator light and a power indicator light for easy visibility. Technical specifications Battery Type: 2000mAh rechargeable lithium battery x 2 (built-in) Working Temperature: -20 ~ 55°C Wireless Distance: 1000m (unobstructed) / 20-50m (obstructed) Wireless Frequency: 410~490 MHz Working Hours: More than 8 months for outdoor unit, about one week for indoor unit Outdoor Unit Size: Approx. 121.5x61.5x31.3mm / 4.78x2.42x12.32inch Indoor Unit Size: Approx. 115x55x20mm /