【How To Use】In addition to the indoor unit's existing display, only one external screen can be connected. The recommended combination is: Indoor unit screen + Outdoor unit doorbell + Extended screen (only one). 【Connect From Anywhere in Your Home】Whether you’re in the living room, kitchen, or upstairs study, you can have real-time video conversations with visitors at your door. 【One Tap to Let Visitors In】Even when you’re busy in the kitchen, you can easily unlock the door using the Add-on Monitor. 【Easily Talk to Visitors at Your Door】Perfect for multi-story homes, the extension monitor lets you talk to visitors instantly from your living room, kitchen, bedroom, or upstairs office. 【Easy Setup, Ready To Use】Step 1 Pair with the SwitchBot App. Step 2 Place Add-on Monitor in an area with strong WiFi., Manufacturer: Wonderlabs