3-Room Wireless Intercom System for Home or Office Expandable system. Package includes set of 3 intercom units but you can add as many additional intercoms as you wish. No AC Power or wires needed! Wireless intercom requires no connection to wall power and is completely wireless (but power adaptor CAN be used if you desire). Wireless intercom works on four AA batteries for up to 12 months without ever being turned off! Effective transmission range from unit to unit of 1000 Feet. Allows TWO-WAY, digital voice communication. Paging function allows you to broadcast to all stations and then speak to the responding station privately! See below for more details on this product: