The 20T Series (2 inch/51 mm dial) Switchgauge model is diaphragm-actuated, temperature-indicating gauge, with built-in electrical switches for tripping alarms and/or shutdown devices. These vapour actuated gauges feature a sealed capillary tube and a sensing bulb. When subjected to heat, the liquid in the sensing bulb changes to vapour creating pressure against the diaphragm mechanism. The diaphragm translates this vapour pressure into a mechanical gauge reading. The gauge pointer acts as a temperature indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contacts are grounded through the Swichgauge case. They have self-cleaning motion to enhance electrical continuity. The gauge mechanism is enclosed in a steel case coated to resist corrosion. A polycarbonate, break-resistant lens and a polished stainless steel bezel help protect this rugged, built-to-last instrument. Ranges are available from 32-120°F (0-45C) thru 300-440F (160-220C).