Allow visitors to ring your doorbell from a second location, such as a back door or a gated driveway, by adding an additional IST V510 Smartphone Video Doorbell to your IST Video Doorbell Entry System. This video doorbell station works just like your original video door unit. When the camera detects motion or a visitor presses the call button on the video doorbell, you'll receive an alert on the indoor monitor and your smartphone. You'll then be able to see and communicate with visitors at your front door without having to open your door.