PLEASE READ THE MANUAL CAREFULLY BEFORE INSTALLATION: in case of any difficulty please Contact customer care number mentioned on the box. Plug n Play Just connect both sets as per the diagram. Plug the Power adopter (provided with system) to the main supply line. Connect the Power adopter to any set. Press the number of other set, the other handset will start ring and communication can be initiated by simply picking up the receiver of other side.The Sonics 1+3 intercom system is best to be used as an intercom system , In small offices, shops indifferent rooms/ floors in houses etc. It is extremely easy to install and use