The A20T Series (2 inch/51 mm dial) Switchgauge models are diaphragm-actuated, temperature-indicating gauges, 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 a 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 that completes a circuit when it touches the adjustable limit contact. Contact(s) are isolated from ground. They have self-cleaning motion to enhance electrical continuity. All models of these rugged, built-to-last instruments are fully sealed from the environment by the unique combination of a polycarbonate case and lens, a polished stainless steel bezel, and O-ring seals. Ranges are available from 32-120°F (0-45°C) thru 300-440°F (160-220°C).