The video door intercom corded indoor panel m e modern electronics vdv 507 ss detached black stainless steel is individual video indoor unit for setting up a video door intercom system you can choose between 1 or 2 family outdoor units from the vdv series this door intercom system impresses with its sophisticated ultra thin design and excellent voice quality this system is expandable to 4 outdoor and 4 indoor units regardless of the number of individual components you only need one power s