Editing Pendulum clock (section)

==Escapement==
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[[File:Anchor escapement animation 217x328px.gif|thumb|upright=1.3|Animation of an [[anchor escapement]], one of the most common [[escapement]]s used in pendulum clocks ]]

The escapement is a mechanical linkage that converts the force from the clock's [[wheel train]] into impulses that keep the pendulum swinging back and forth. It is the part that makes the "ticking" sound in a working pendulum clock. Most escapements consist of a wheel with pointed teeth called the ''escape wheel'' which is turned by the clock's wheel train, and surfaces the teeth push against, called ''pallets''. During most of the pendulum's swing the wheel is prevented from turning because a tooth is resting against one of the pallets; this is called the "locked" state. Each swing of the pendulum a pallet releases a tooth of the escape wheel. The wheel rotates forward a fixed amount until a tooth catches on the other pallet. These releases allow the clock's wheel train to advance a fixed amount with each swing, moving the hands forward at a constant rate, controlled by the pendulum.

Although the escapement is necessary, its force disturbs the natural motion of the pendulum, and in precision pendulum clocks this was often the limiting factor on the accuracy of the clock. Different escapements have been used in pendulum clocks over the years to try to solve this problem. In the 18th and 19th centuries, escapement design was at the forefront of timekeeping advances. The anchor escapement (see animation) was the standard escapement used until the 1800s when an improved version, the [[deadbeat escapement]], took over in precision clocks. It is used in almost all pendulum clocks today. The [[remontoire]], a small spring mechanism rewound at intervals which serves to isolate the escapement from the varying force of the wheel train, was used in a few precision clocks. In [[tower clock]]s the wheel train must turn the large hands on the clock face on the outside of the building, and the weight of these hands, varying with snow and ice buildup, put a varying load on the wheel train. [[Escapement#Gravity escapement|Gravity escapements]] were used in tower clocks.

By the end of the 19th century specialized escapements were used in the most accurate clocks, called ''astronomical regulators'', which were employed in naval observatories and for scientific research. The Riefler escapement, used in Clemens-Riefler regulator clocks was accurate to 10 milliseconds per day. Electromagnetic escapements, which used a switch or [[phototube]] to turn on a solenoid [[electromagnet]] to give the pendulum an impulse without requiring a mechanical linkage, were developed. The most accurate pendulum clock was the Shortt-Synchronome clock, a complicated electromechanical clock with two pendulums developed in 1923 by W.H. Shortt and [[Frank Hope-Jones]], which was accurate to better than one second per year. A slave pendulum in a separate clock was linked by an electric circuit and electromagnets to a master pendulum in a vacuum tank. The slave pendulum performed the timekeeping functions, leaving the master pendulum to swing virtually undisturbed by outside influences. In the 1920s the Shortt-Synchronome briefly became the highest standard for timekeeping in observatories before quartz clocks superseded pendulum clocks as precision time standards.