How does a visual doorbell take photos?

A visual doorbell has a physical button that allows visitors to trigger calls to you. You will receive app notifications and can view photos taken by the doorbell camera in the app. If the visual doorbell is embedded with a motion detector, such as a PIR sensor, image recognition device, or radar detector, you can set a sensitivity level to enable the doorbell to take a photo when no motion is detected within a specified time. For example, the visual doorbell automatically takes a photo and sends it to your mobile phone when it detects no motion within 5s if you set the sensitivity to a high level or within 10s if you set the sensitivity to a low level.