The user can communicate with the visitor through the built-in intercom by pressing the “Push-to-Talk” button. If a visitor is unfamiliar, the user can ask the visitor to show his/her ID documents and take pictures of the ID manually by pressing the “camera button”. Pictures of each visitor will be taken automatically and stored in the memory. When user returns, he/she can review images of visitors stored in the memory. Users can easily identify suspicious persons who check out their home frequently.