A machine for measuring time, indicating the hour and other divisions; in ordinary mechanical clocks for domestic or office use the time is indicated on a typically circular face or dial plate containing two hands, pointing to numbers engraved on the periphery of the face, thus showing the hours and minutes. The works of a mechanical clock are moved by a weight or a spring, and it is often so constructed as to tell the hour by the stroke of a hammer on a bell. In electrical or electronic clocks, the time may be indicated, as on a mechanical clock, by hands, but may also be indicated by direct digital readout, with the hours and minutes in normal Arabic numerals. The readout using hands is often called analog to distinguish it from the digital readout. Some clocks also indicate the seconds. Clocks are not adapted, like the watch, to be carried on the person. Specialized clocks, such as atomic clocks, may be constructed on different principles, and may have a very high precision for use in scientific observations.
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