Another challenge was developing a movement that could manage the energy necessary to power the Sonnerie functions, as well as the repeater functions, by means of a single mainspring barrel. This barrel’s spring can be wound either partially, by activating the repeater slide on the case middle at 9 o’clock, or more fully, by rotating the crown counter-clockwise. A second barrel, which powers the watch’s timekeeping functions, holds 50 hours of power reserve and is wound by a traditonal clockwise turn of the crown.
Every hour, the melodic “Sol” note sounds from the 46-mm, white-gold case of the Ulysse Nardin Imperial Blue, unless the wearer wishes the watch to remain quiet for a while, in which case he can use the “on/off” pusher in the back of the case at 11 o’clock to silence the mechanism. Activating the Westminster chimes of the minute repeater, by engaging the slide at 9 o’clock, sets the hammers and gongs in motion on the dial side of the movement, on either side of the flying tourbillon, treating the wearer to a miniature, mechanized musical performance. Ulysse Nardin also included a safety system in the crown for winding the skeletonized hour and minute hands, which will stop the chimes while the time is being reset. The Ulysse Nardin Imperial Blue, a limited edition of only 20 pieces worldwide, comes on a dark blue strap with folding buckle.