Editing Clock (section)

===Controller===

This has the dual function of keeping the oscillator running by giving it 'pushes' to replace the energy lost to [[friction]], and converting its vibrations into a series of pulses that serve to measure the time.
* In mechanical clocks, this is the [[escapement]], which gives precise pushes to the swinging pendulum or balance wheel, and releases one gear tooth of the ''escape wheel'' at each swing, allowing all the clock's wheels to move forward a fixed amount with each swing.
* In electronic clocks this is an [[Electronic oscillator|electronic oscillator circuit]] that gives the vibrating quartz crystal or tuning fork tiny 'pushes', and generates a series of electrical pulses, one for each vibration of the crystal, which is called the [[clock signal]].
* In atomic clocks the controller is an evacuated microwave [[Cavity resonator|cavity]] attached to a microwave [[Electronic oscillator|oscillator]] controlled by a [[microprocessor]]. A thin gas of [[caesium]] atoms is released into the cavity where they are exposed to microwaves. A laser measures how many atoms have absorbed the microwaves, and an electronic feedback control system called a [[phase-locked loop]] tunes the microwave oscillator until it is at the frequency that causes the atoms to vibrate and absorb the microwaves. Then the microwave signal is divided by [[digital counter]]s to become the [[clock signal]].<ref>{{cite book| url = https://books.google.com/books?id=Z7chuo4ebUAC&pg=PA61| title = Jespersen 1999, pp. 52–62| isbn = 978-0-486-40913-9| last1 = Jespersen| first1 = James| last2 = Fitz-Randolph| first2 = Jane| date = January 1999| publisher = Courier Corporation| access-date = November 6, 2015| archive-date = July 3, 2023| archive-url = https://web.archive.org/web/20230703114216/https://books.google.com/books?id=Z7chuo4ebUAC&pg=PA61| url-status = live}}</ref>
In mechanical clocks, the low [[Q factor|Q]] of the balance wheel or pendulum oscillator made them very sensitive to the disturbing effect of the impulses of the escapement, so the escapement had a great effect on the accuracy of the clock, and many escapement designs were tried. The higher Q of resonators in electronic clocks makes them relatively insensitive to the disturbing effects of the drive power, so the driving oscillator circuit is a much less critical component.<ref name="Marrison" />