This Add-on Video Doorbell requires Blink sync module which is not included

• Video Doorbell is our second-generation smart security doorbell with up to two years of battery life, an expanded field of view, and improved security features for more peace of mind, no matter where you are.
• Last longer with two-year battery life — Experience up to two years of continuous security coverage with three included AA Energizer lithium batteries and a Blink Sync Module (sold separately).
• See more at your door — Greet guests and watch packages get delivered, day and night, with head-to-toe HD view and infrared night vision. Use two-way talk to hear and speak through the Blink app.
• Set up in minutes — Easily install wire-free or connect Video Doorbell to existing doorbell wiring. When wired, Video Doorbell will sound through your home. Without wiring, you can use your Blink Mini 2 camera (sold separately) as an indoor plug-in chime. You'll also get alerts on your Blink app with each doorbell press.
• Always know who's there — As part of a Blink Subscription Plan (sold separately), get alerts whenever a person is detected and enjoy features like Blink Moments, which stitches together clips into a single video to save and share.
• Save and share clips — Securely store your footage in the cloud with a free 30-day trial of a Blink Subscription Plan (sold separately).
• Works with Alexa — Connect to an Alexa-enabled device to answer the front door, arm and disarm your smart home system, and more using your voice.
• Includes one Video Doorbell with three AA Energizer lithium batteries and a mounting kit (including screws and anchors). Required Sync Module (sold separately) not included.