Intercom Systems - Imagine the convenience of knowing who's at your door before you open it. Add to that the ability to see as well as hear who is there. Used in place of the standard doorbell, an intercom system provides not only the advantage of knowing who's there, but the peace of mind as well. Doorbell intercom systems add security to convenience, allowing you to answer the door and open it from any telephone in the house, even a cordless phone.