... wireless audio door phone 1.communication distance: more than 300 meters 2.max combination: 99 pcs 3.high clear voice 2.4GHz wireless ... 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, ... mode and return to setting status. Wireless intercom system