This wireless doorbell intercom system includes one outdoor unit and four indoor units. All units are pre-paired and ready to use right out of the box. No wiring is required. Important Note on Operation Indoor units cannot actively call the outdoor unit. When someone rings the doorbell, the outdoor unit initiates a call to all four indoor units, and two-way communication begins. Indoor units can call each other freely. Easy to Use The system operates on 3 channels (A, B, and C). No additional setup is needed. Basic intercom functionality only. Long Range Two-Way Communication Wireless range reaches up to 4,900 feet in large open spaces. Whether in a multi-story house, a courtyard, or a small business, the signal stays strong and reliable for everyday use. Battery Operated with Charging Bases All units come with built-in rechargeable batteries. Each indoor unit includes a convenient charging base. Low battery alerts keep you informed, so you are never caught off guard. Designed for Home & Business Use Operating temperature range: -4°F to 122°F. Features include a 3.5mm audio jack, 3 adjustable volume levels, and 20 ringtones. Suitable for homes, cafes, gas stations, offices, and other commercial use. Four Indoor Units for Multi-Room Coverage With four indoor units, you can place one in the living room, bedroom, kitchen, basement, or office. When the outdoor unit is pressed, all four indoor units ring simultaneously – allowing anyone in the house to respond. Expandable System Easily add more indoor or outdoor units to build a flexible intercom network. Indoor units can call each other freely. Any outdoor unit can initiate a call to indoor units. Indoor units cannot actively call outdoor units – they respond when called.