 When a notification is received, the user will typically see a live video stream from the device, clearly showing who is the door and they can engage in a 2-way audio conversation.The devices can be powered by an internal battery, or they may use the existing bell wiring for continuous power.The video is typically recorded direct to a cloud internet service, meaning that if the unit is tempered with, damaged or stolen then this event will be captured and can be analysed to determine the identity of the responsible party.