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:
“I have seen in this revolution a circular motion of the sovereign power through two usurpers, father and son, to the late King to this his son. For ... it moved from King Charles I to the Long Parliament; from thence to the Rump; from the Rump to Oliver Cromwell; and then back again from Richard Cromwell to the Rump; then to the Long Parliament; and thence to King Charles, where long may it remain.”
—Thomas Hobbes (1579–1688)
“Her face had the seamed reserve of the old in this country [Japan]. It was a neighborhood poignantly rich in old ladies.”
—Angela Carter (1940–1992)