Flyback and Split Seconds Chronograph Functions

Flyback. In a conventional chronograph, a button is depressed to start the counter, a second press of the same button is required to stop it, and another button is depressed to reset the chronograph seconds hand back to zero. Restarting the counter would require three button presses: Stop-Reset-Start.

Officine Panerai Luminor 1950 8 days Chrono
Monopulsante GMT PAM 00317 is a chronograph
with the flyback feature. You can read more about it here.

The flyback complication was developed to allow a quick restart of the chronograph from zero with a single button press.

Split Seconds. The basic chronograph allows the measurement of a single event, and soon watchmakers began searching for a way to simultaneously measure multiple events beginning at the same time.

This was done by having two chronograph seconds hand, one of which could be stopped while allowing the second one to continue moving. This complication was called the split-seconds chronograph. A split-seconds chronograph features a clutch system with clamps that connect and disconnect the split-seconds hand and the main chronograph hand. A third button is added to the chronograph to activate the stopping of the split-seconds hand. Pressing this third button again allows the split-seconds hand hand to catch up with the chronograph hand, and the two hands, superimposed, continue together.

Patek Philippe Ref. 5004. The Patek Philippe Ref. 5004 is Splits Seconds Chronograph with a Perpertual Calendar. Button at 2 o'clock starts and stops the chronograph button while the one at four o'clock resets the chronograph hands back to zero. The button on the crown is to stop and release the Splits Seconds hand. When released, the Splits Seconds hand catches up with the main chronograph hand.