• All Call between stations in same residence / Office™ Option button – r external device control (N/O dry contact, AC/DC 24" 1.6A Max)• Call tone volume control with LED mute indicator• Receive volume control• Optional Call Extension Speaker (IER-2)• Optional external signaling to 3rd party bell or light using RY-ES (used in lieu of IER-2)• Door release button – owered by door station)