Control apparatus for an environmental control system comprises input circuitry receiving environmental information and output circuitry for controlling an HVAC system. Processing circuitry in the controller configures the output circuitry based at least in part on the signals received on the input circuitry....http://www.google.de/patents/US6176436?utm_source=gb-gplus-sharePatent US6176436 - Method and apparatus for energy recovery in an environmental control system
