The chronograph is a wristwatch like Rolex Thailand with a stop function, which means that it can display the time and a stopped period. Second, minute and hour counters can be started and controlled separately. A clock can usually be recognized by two pushers, which are located next to the crown on the flank of the case, and by the small totalizers (sub-dials) on the dial. They usually show the hours and minutes of the stop time and the seconds of the time, while the stopped seconds are shown centrally. An integrated stop function is one of the most sought-after and valuable additional functions.
Due to many parts, the many springs, wheels, and levers, the chronograph complication is very complex to implement. The stopping process is usually started and stopped again by pressing the upper trigger on the housing flank. When the desired length of time has been measured, the wearer uses the bottom pusher to zero the stop hands. To ensure that the zero position goes smoothly, levers push heart-shaped disks, which sit on the axis of the pointer, back into the starting position. To be able to stop the time with the mechanical clock, engaging and releasing the locked wheels must happen at the same time. This complex chronograph circuit can be set using a traditional column wheel or a modern cam control.
There are also various solutions for the clutch itself. The clutch brings the gears of the base movement into engagement with the chronograph gear. The classic – and most beautiful – form of the chronograph clutch is the horizontal gear clutch (photo below). Here, the wheels involved are visible next to one another and are brought into engagement when the clock is started. To do this, the clutch lever, controlled by the ratchet wheel, pushes the small clutch wheel (top left), which is always in mesh with the second wheel of the movement (below), up to the Chrono center wheel (center).