Bottom right is small ink bottle filled with mercury and tightly corked. The cork has a glass tube through the center and one electrode through the cork top into the mercury and connected to ground.
Mercury goes part way up glass tube (add mercury through tube if necessary). Second electrode is pushed through rubber to slide electrode to level we want temperature alarm to go off. (To simulate closed circuit close switch in square area). Alarm (shown as lamp) can turn on light, buzzer or another circuit.
Important that one side of this rubber sleeve has slot to allow air to flow in and out as mercury changes with temperature.
