KCV-301 4 Wire • 3.5" Digital color LCD(NTSC/PAL) • Communication with door and door monitoring • Door open during communication • Easy & simple installation with only 4 wires • Intercom function between extended indoor units • Surface mount type installation • External 64 cut memory equipment (KVR-300) connection -(B/W)*option • Connection with up to 2 door cameras, 2 monitors and 2 sub audio phone (KDP-602G)*option • 5 melody selection