Intercom Doorbell System Wireless 15 Ringtone 3 Volume 2 Way Voice Doorbell for Home Apartment1[Wireless Intercom System] This intercom doorbell kit includes one outdoor unit and two indoor units, allowing for intercom communication. The indoor units can also communicate with each other. 2[Multi Functional] With 15 selectable ringtone options and three adjustable volume levels, you can choose the perfect ringtone and volume to suit your preferences and needs. 3[Extended Transmission Range] The wireless transmission distance can achieve up to 200 meters in an open area, and 5 to 50 meters with obstacles, ensuring reliable communication. 4[Expandable Intercom System] This intercom doorbell system is expandable, allowing you to add additional indoor or outdoor units to your system, compatible with almost any indoor or outdoor installation. 5[Intelligent Power Saving] Equipped with intelligent power saving chip, this 2 way voice doorbell offers exceptional battery life. After a full charge, it can be used for over six months under normal usage.