Chamberlain NTD2 Wireless Indoor/Outdoor Intercom-Weather Resistant Portable wireless intercom system can be added to an existing Chamberlain intercom system. Crystal clear, secure 900MHz digital communication. 1,000 FT range with no wires or power connection required and battery-powered design for easy setup. Weather resistant for outdoor applications. Compatible with the following Chamberlain wireless intercoms - NDIS, NLS1, and NLS2-Sold Separately.