Thermostat with improved temperature sensing circuit

Claim 1

A thermostat with an improved temperature response circuit comprising in combination: a temperature responsive circuit, said circuit having two power supply terminals with a temperature sensitive impedance in one circuit branch between said terminals and a calibration impedance in another circuit branch between said terminals; a variable, set point, offset impedance; a set point, offset control coupled to said offset impedance; a control logic circuit; means for selecting heating and cooling operating modes; first means coupled to said logic circuit for producing an output signal of one binary significance when said heating mode is selected; second means coupled to said logic circuit for producing an output signal of the other binary significance when a cooling mode is selected; a timing circuit coupled to said logic circuit and producing a cyclical output signal of one binary significance for part of a cycle and the other binary significance for part of said cycle; said logic circuit producing, respectively, a first control output, a second control output, or a third control output in response to the binary state of the output of said timing means, and the output of said first means and said second means; and means responsive to said logic circuit outputs to connect said variable set point offset impedance in series with said temperature sensitive impedance in response to said first output, or in series with said calibration impedance in response to said second output.