Dreyfuss modernized the appearance of Honeywell’s thermostats in the 1930s; among the first was the Chronotherm, which incorporated a “digital” clock into its display. Dreyfuss was frustrated, however, that rectangular thermostats never seemed to hang squarely on the wall. Work began on a round thermostat in 1940. Placing all the elements in a circular form was more difficult than it first seemed; attempts to make a curved thermometer were especially problematic. World War II halted the development program but helped provide technical solutions.
Henry Dreyfuss, Honeywell, thermostat