This is a special edition of the D21* series that has no fascia or bracket system. It is designed purely for engineering and integration. Companies looking to test the Doorbird system for their customers, or write custom integrations to SIP phones and other systems, can buy this model for lower cost and without the finishing touches required by the end user. Connects to App on Smartphone or Tablet 180 - 720p HDTV Camera with Audio Surface Mounted Connect to and Control Electric Door/Gate Connect to leading brand Smartlocks, CCTV, and NAS Devices Connect to Press to Exit Button Motion Sensor Night Vision Ethernet Smart Home Compatible with many platforms Visitor History snapshots with date and time, within app Up to 8 Devices can connect to a Doorbird Up to 10 Doorbird devices can connect to the app