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:
“Falling in love with a United States Senator is a splendid ordeal. One is nestled snugly into the bosom of power but also placed squarely in the hazardous path of exposure.”
—Barbara Howar (b. 1934)
“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)