... 99 pcs 3.high clear voice 2.4GHz wireless audio door phone,supporting 99 pcs intercomElectrical Features1. Using 2.4G ISM ... process, press button 3 on master phone, press button 5 on extention phone, when in receiving code, press button ... 4 on the master phone, press button 5 on extention phone.ID setting, Coding, Give code, ... return to setting status. 2.4GHz wireless audio door phone