The Burg-Wächter Video Door Intercom Door eGuard Video Bell DG8500 is a 2.4 GHz Wi-Fi-based video door intercom module designed for use and replacement of existing two-wire doorbell systems with 8 - 20 Vac alternating current supply. When the doorbell button is pressed, the chime is triggered, and a push notification is sent to your smartphone simultaneously. You can access the system from anywhere and communicate with the person or people at your door. The built-in battery is charged by the power supply when the button is pressed.