William O. Douglas

“ It accordingly held that the patent laws permit and the anti-trust laws do not forbid the control over the sale and use of the unpatented device which Minneapolis-Honeywell sought to achieve through its licensing agreements. We do not agree, even though we assume the patent to be valid. ”

“ The Freeman patent, as found below, covers a system of hot air furnace control which requires three thermostats for its operation. A room thermostat starts the stoker. Another thermostat (or limit switch) breaks the stoker circuit when the air in the furnace reaches a predetermined temperature, irrespective of the fact that the room thermostat may still call for heat. This second thermostat operates to prevent unsafe conditions due to overheating. The third thermostat is also in the furnace. It controls a fan which forces hot air from the furnace to the rooms. ”

“ Neither the petitioner nor the respondent sells or installs the Freeman system in furnaces; that is to say, they do not practice the invention. They are competitors in supplying the switch to control the fan and limit circuits employed in such systems. ”