Please refer to the photo below for the names of the parts referred to in this text. When the upper push-button is pressed, the operating lever pulls the pillar wheel by one notch, which causes the blocking lever (or brake) to move out of the way and free the chronograph runner. The pillar wheel also causes the sliding gear assembly to move towards the center, pushed by the coupling clutch spring, causing the sliding gear to engage the chronograph runner. The pillar wheel also causes the hour clutch lever to move, causing the sliding gear assembly on the front of the pillar plate to engage the hour recording wheel (see the last photo on the main page). The chronograph is now running. After every minute a small arm on the chronograph runner moves the intermediate wheel by one tooth, which moves the minute recording wheel by one tooth. The second recording hand is mounted onto the chronograph runner. The minute recording hand is mounted onto the minute recording wheel. The hour recording hand is mounted onto the hour recording wheel.
Push the upper push-button again and the chronograph stops: the two sliding gear assemblies move away from the chronograph runner and the hour recording wheel, and the blocking lever moves against the chronograph runner to stop it.
Push the lower push-button to reset the chronograph hands to zero: the reset lever pushes the hammer against the heart-shaped cams on the chronograph runner and the minute recording wheel to move the second and minute recording hands to zero. The hammer momentarily moves the blocking lever away from the chronograph runner while the latter is being reset to zero. The reset lever also pushes the hammer on the front of the pillar plate against the heart-shaped cam on the hour recording wheel to move the hour recording hand to zero.