THE PATENTED ZERO-RESET
With the ZERO-RESET mechanism, the movement stops and the seconds hand jumps to zero when the crown is pulled. This allows the watch to be accurately synchronised.
The mechanism consists of a complex lever system that presses a zero-reset lever against a heart-shaped cam. The seconds hand is attached to the same arbor on which the heart cam rotates. When the heart cam is pivoted into its initial position by the zero-reset lever, this also causes the seconds hand to jump to zero. Pushing the crown home again instantly restarts the movement and with it the seconds hand.
In a modified, even more complex form, this mechanism can also be found in the 1815 TOURBILLON except that here, the tourbillon must be stopped instead of the balance.