If your home or business has more than 1 HVAC system and you're looking to add remote thermostat control without wires, purchase the Totaline Wireless Thermostat System (shown below) and then buy this receiver (one for each HVAC system). Detail & Specifications: The receiver is easy to install and is wired just like a standard 24VAC thermostat.
Specifications
Totaline/ Venstar Telephone Interface System allows you to call and "talk" to your compatible thermostat. Monitoring and controlling your thermostat is now simple and easy from any phone, from anywhere.