The simplest temperature controllers—they turn devices fully on or off, with no middle state, at a given temperature. They’re best as alarms and for systems where temperature changes slowly, but they shouldn’t be used when precise temperature control is necessary. All automatically reset as the temperature fluctuates. To read the temperature, they use a highly sensitive thermocouple probe (not included). And their mechanical relay actuates circuits directly. Controllers are SPDT (single pole, double throw) and can turn one circuit from off to on (normally open) or on to off (normally closed). Mount them into cutouts in instrument panels.

All meet American, Canadian, and European safety standards.