A pneumatic sensing apparatus for use in an overheat or fire alarm system, comprising: a pressure sensor a sensor tube containing a pressurized gas in communication with the pressure sensor configured to sense a temperature variation based on changes of the pressurized gas; a pressure switch coupled to the pressure sensor, wherein the pressure switch includes a signal transducer configured to provide an output indicative of an overheat or fire alarm condition, and further wherein the pressure switch includes an alarm switch; a controller; a memory; and a processor, wherein the pressure switch further comprises a variable resistor in electronic communication with the alarm switch, the signal transducer and the controller, the variable resistor configured to measure a change in resistance, wherein the change in resistance is indicative of a temperature and pressure change of the pressurized gas; further wherein the controller is in electronic communication with the memory, the processor, and the alarm switch, wherein the memory includes instructions recorded thereon that, when read by the processor, cause the processor to: compare the measured change in resistance to ranges of the signal transducer; determine if the measured change in resistance is indicative of a normal condition or an overheat condition; and activate the alarm switch when the measured change in resistance is indicative of an overheat condition, and characterised in that the processor is configured to continuously receive the change in resistance data and provide a temperature curve based on the continuously received data. a pressure sensor a sensor tube containing a pressurized gas in communication with the pressure sensor configured to sense a temperature variation based on changes of the pressurized gas; a pressure switch coupled to the pressure sensor, wherein the pressure switch includes a signal transducer configured to provide an output indicative of an overheat or fire alarm condition, and further wherein the pressure switch includes an alarm switch; a controller; a memory; and a processor, wherein the pressure switch further comprises a variable resistor in electronic communication with the alarm switch, the signal transducer and the controller, the variable resistor configured to measure a change in resistance, wherein the change in resistance is indicative of a temperature and pressure change of the pressurized gas; further wherein the controller is in electronic communication with the memory, the processor, and the alarm switch, wherein the memory includes instructions recorded thereon that, when read by the processor, cause the processor to: compare the measured change in resistance to ranges of the signal transducer; determine if the measured change in resistance is indicative of a normal condition or an overheat condition; and activate the alarm switch when the measured change in resistance is indicative of an overheat condition, compare the measured change in resistance to ranges of the signal transducer; determine if the measured change in resistance is indicative of a normal condition or an overheat condition; and activate the alarm switch when the measured change in resistance is indicative of an overheat condition, and characterised in that the processor is configured to continuously receive the change in resistance data and provide a temperature curve based on the continuously received data.