2.4G wireless audio door phone 1.communication distance: more than 300 meters 2.max ... : 99 pcs 3.high clear voice 2.4GHz wireless audio door phone,supporting 99 pcs intercomElectrical Features1. Using 2.4G ISM ... code, press button 4 on the master phone, press button 5 on extention phone.ID setting, Coding, Give code, Receive ... mode and return to setting status. 2.4GHz wireless audio door phone