patents that have been handed out to people for updating and upgrading this device. Automatic, non-digital chronographs do not require a battery, because the arm or wrist of the wearer creates kinetic energy, which results in the total energy source needed for this device to work. Throughout the day, while the wearer of the watch is walking, the swinging motion of his arm forces a semicircular rotor to turn on a pivot within the watch. The rotor is attached to a ratchet that winds the mainspring in the watch, so that it is ready for use at all times. The modern day chronograph works by pushing a start button, normally located at the two o'clock position, to begin recording time, and by pushing the same button to stop the recording. When the button is pushed to start the recording, a series of three (in more complicated and more precise chronographs there are more wheels) train wheels start turning. The smallest has a revolution time of one second, the next sixty seconds, and the final one has a revolution time of sixty minutes. The three train wheels interact with one another and record how long it has been since the start button has been activated. In addition to the start button, it also features a reset button normally located at the four o'clock position. When the reset button is pushed the chronograph hand will reset back to zero. Tachymeter bezels are a complication that allows rapid calculations of speed or distance. Rotating bezels allow for more complex calculations or repeated calculations without requiring a reset of the timer. Types The original chronographs that Rieussec invented were called tape chronographs. They consisted of a tape that was constantly being dragged along at a controlled speed. When activated, a pen would be pushed onto the tape and begin recording until deactivated. Specialized chronographs are used by deep sea and scuba divers. While basic functionality is the same as other chronographs, diving models have longer and more practical straps to wear over equipment, are made to be waterproof to deeper depths, have more rounded corners to prevent catching and luminous dials for reading in the murky depths. Also divers chronographs are fitted with large bezels that have at least one luminous marking: at the start of a dive the bezel is rotated to place the marking at the extent of time allowed by the