The Trane CNT3671 SPST Pressure Switch 0.20" WC is a genuine HVAC safety control designed to monitor air pressure within compatible Trane furnaces and heating systems. It works by detecting the required pressure created by the inducer motor and closing the electrical circuit only when proper airflow is present, allowing the heating cycle to operate safely. https://www.partshnc.com/20wc-spst-pressure-switch-4