Additional iQ3 2.1 Door Kit with J-Track SensorThe Tailwind iQ3 2. 1 Door Kit includes a rugged, commercial grade J Track mount door sensor and provides you with everything you need to connect another door to your Tailwind IQ3 2. 1 controller. Each Tailwind IQ3 2. 1 controller can control and monitor up to 3 doors using dry contact control. Please check our SmartFit Guide before ordering. Not all garage door openers compatible. This door kit is NOT compatible with the original (1st generation)