• Door release powered by door station without the need of an additional transformer• Backlit directory• All Call between stations within same tenant residence or Office™ Option button – control an external device• Call tone volume control with mute indicator• Convenient box set is complete with a tenant master station, a 1-call entrance station, and a power supply• (up to 3 more tenant master stations and 15 tenant sub stations can be added for a full 1 x 4" 16 system)• Optional call extension speaker