Power Reserve Indicator
Some high grade watches have an extra dial on the face indicating how much power is left in the mainspring, often graduated in hours the watch has left to run. Since both the arbor and the barrel turn, this mechanism requires a differential gear that measures how far the arbor has been turned, compared to the barrel.
Read more about this topic: Mainspring
Famous quotes containing the words power and/or reserve:
“There is something else which has the power to awaken us to the truth. It is the works of writers of genius.... They give us, in the guise of fiction, something equivalent to the actual density of the real, that density which life offers us every day but which we are unable to grasp because we are amusing ourselves with lies.”
—Simone Weil (1909–1943)
“We must reserve a back shop all our own, entirely free, in which to establish our real liberty and our principal retreat and solitude.”
—Michel de Montaigne (1533–1592)