Watch is a device for measuring the current time (seconds, minutes, hours). Watches are classified as timing devices, which also includes timer, stopwatch, timer and time relay. The first device by which people measured the time was the sundial. In ancient Egypt and Greece, while counting down to the solar watch with horizontal or vertical dials. Along with the sundial a water clock that displays time, day or night is built in the 2nd and 1st millennium in India, China, Egypt and Greece. The simplest types of water clocks were a vessel with the scale, scaled in units of time. In a vessel drop by drop, came out of the water filled to the brim (from an external source) reservoir. Constant pressure of water in the reservoir ensures a uniform filling of the vessel and even increases the level of water in it, noted on the scale. Uniform motion is the basis for the operation and some other types of watches, including sand. Great importance to improve the accuracy of watches was the discovery by Galileo isochronous small oscillations, i.e. the independence period of oscillation of the amplitude. Galileo about 1640 proposed a new trigger, resembling modern, but his idea was not implemented. The inventor of the modern types of mechanical watches is considered to be C. Huygens, who in 1657 used a pendulum as a regulator clock. The increased precision of movements set minute hands in pocket types of watches and about 1760 began to use the clock second hands. Significant impact on the precision of the pendulum temperature change provides in particular the balance types of clocks. By appointment watches are divided (arbitrarily) to the household and special types. Depending on the use of differentiated consumer-watches, pocket, table, wall, street, tower types of clocks. Depending on the destination allocate specialized types of watches for scuba diving, traveling, antimagnetic, etc. There is a large group of special watches official appointments: alarm, time and attendance, procedural, policy, etc. The types of oscillatory systems used in modern watches are distinguished pendulum, balance, tuning forks, and quartz and quantum types of watches. There is electric clock running on AC power. These clocks are secondary, and the role of the primary power generator performs. The most common is mechanical watch with a mechanical (spring-loaded, weight-lifting) drive. The basic unit of modern mechanical type of watch is an engine, the system of wheels, move or trigger, control, switch gear and winding mechanism.
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