A pressure switch assembly is used with a furnace controller having a first input and a second input. A first pressure switch is configured to actuate at a first combustion pressure level and is connected to the first input. A second pressure switch is configured to actuate at a second combustion pressure level, and a third pressure switch is configured to actuate at a third combustion pressure level. Pressure signals provided on the second input from at least one of the second pressure switch and the third pressure switch are used by the furnace controller to derive actuation states of the second and third pressure switches.