The document describes a temperature controller circuit that uses an LM335 temperature sensor, comparator, amplifier, and Darlington pair to control a relay based on temperature. When the sensed temperature exceeds the reference voltage, the comparator switches the Darlington pair to activate the relay. The circuit is intended to control devices like refrigerators and AC units by turning the compressor on and off based on temperature. It provides an easy to build, low complexity temperature control solution.