Intercom Central PLC166 TRADITIONAL 2 prongs Power-line HOME Intercom System for 110 Volts only A Cost Effective REPLACEMENT for your existing 2 prong syste. Just plug them into the outlet of your existing intercoms.. Setup is Required, Setup Steps included. Don't waste your time for a blind outlet hunt. Traditional 2 prongs intercoms uses 1 of the 2 discreet sets of 110 wires in the house. Please read the Product Knowledge -; 2nd picture in the Picture Gallery before buying 3 Channels intercoms with voice activation feature.