When you push the button on one of these devices, the doorbell's camera sends a video feed to your smartphone over Bluetooth or Wi Fi, and you can press a button in the app to talk to the person at the door over a two way speaker. Each doorbell supports ring alerts, which notify your phone when a person rings the bell, as well as motion alerts, which can be a little more hit or miss. How We Test and Rate Video DoorbellsWe self installed the video doorbells on houses in Massachusetts and California, and tested in real world conditions with friends and family ringing the bells day and night. We evaluated ease of setup, the design and features of the app, how well the app and doorbell kept us notified, and video and audio quality. We also factored in how much you'll pay for cloud storage to save the video. What to Look for When Buying a Video DoorbellPower Requirements: Doorbells typically require 16 volts or more to work. If you have a newer house, this may not be an issue. But as we found out, older homes with more antiquated systems may not deliver enough juice. One of our test houses, which was built in 1946, was sending only about 10 volts of electricity to the existing doorbell, which wasn't enough to power the two doorbells in the roundup that lack built in batteries. After we upgraded the doorbell's circuit to a 20 volt transformer, everything worked as advertised. Most people shouldn't have to upgrade their transformers, especially with newer houses, and the two doorbells that have built in batteries don't require power from the doorbell at all.