A. Lange & Söhne caliber L043.5
When they developed the strikework for this watch, the engineers harnessed the principle of the jumping numerals mechanism: instead of with hands, the time is displayed with an hour ring and two minute discs. This allows three snails connected with these mechanical display elements to separately sample the number of hours, ten-minute intervals, and minutes to be acoustically indicated.
The energy needed by the striking mechanism is provided by the mainspring. When the strikework is activated, the ratchet wheel is uncoupled from the winding train. Therefore, the ratchet wheel can turn freely and power the striking mechanism. This also prevents the winding train including the crown from turning during the repeater sequence, which would imply a loss of energy.
To guarantee the flawless interaction of the complex mechanical ensemble, elaborate safety and blocking mechanisms have been integrated into the movement. While the repeater is working, the switching action of the numerals discs is delayed. At the same time, the crown cannot be pulled and consequently, the time cannot be set. This precaution prevents any interference with the strikework sampling sequence and ensures that the acoustic indication of time precisely corresponds with the digitally displayed time. At 12:59 hrs when the longest series of tones is struck, it takes about 20 seconds until the repeater sequence has ended.