Expand your door intercom system in seconds! This Extra Door Intercom Station for the Wireless 3-Channel Door Intercom System (sold separately) communicates over your home's existing wiring -- no new wiring is required! With this Door Intercom System, you'll be able to answer your doorbell from any room in your home.The Extra Door Intercom Station expands the 3-Channel Door Intercom System and communicates via existing AC wires and will block X10 signals during the period that the intercoms are being used. They will not affect X10 operation if they're plugged in but are not transmitting sound. The door intercom unit easily replaces your existing push-button doorbell using existing doorbell wiring.