A sensor module supplying analog data signals from one of a temperature or pressure sensing element connects to a modular switch system through a D-shaped sensor port in the modular switch housing. The manufacturer and user may modify the standard modular switch system, which includes an internal electrical assembly to be a pressure or temperature switch by applying and removing selected sensor modules. The interconnection between the sensor module and the modular switch system includes particular leads carrying analog data signals and serial digital information signals. These leads are attached to a connector secured to the sensor module substrate. The connector is enclosed in a D-shaped extended portion of a cover which snap fits to an open end of the sensor module base. Mounted on the sensor module substrate are an amplifier, a reference voltage circuit and a non-volatile memory containing calibration data relating to the standardization of output signals from the sensors.