Editing Radio clock (section)

{{Short description|Clock which synchronizes its time using radio transmitters}}
{{Distinguish|text=[[Alarm clock#Clock radio|clock radio]], an alarm clock incorporating a broadcast radio receiver or [[Broadcast clock]]}}
[[File:Atomic clock.jpg|thumb|245px|A modern [[Low frequency|LF]] radio-controlled clock]]

A '''radio clock''' or '''radio-controlled clock''' (RCC), and often colloquially (and incorrectly<ref name="Lombardi"/>) referred to as an "[[atomic clock]]", is a type of [[Quartz clock|quartz]] [[clock]] or [[watch]] that is automatically [[Synchronization|synchronized]] to a [[time code]] transmitted by a [[radio]] transmitter connected to a [[time standard]] such as an atomic clock. Such a clock may be synchronized to the time sent by a single transmitter, such as many national or regional time transmitters, or may use the multiple transmitters used by [[satellite navigation]] systems such as [[Global Positioning System]]. Such systems may be used to automatically set clocks or for any purpose where accurate time is needed. Radio clocks may include any feature available for a clock, such as alarm function, display of ambient temperature and humidity, broadcast radio reception, etc.

One common style of radio-controlled clock uses time signals transmitted by dedicated terrestrial [[longwave]] radio transmitters, which emit a time code that can be demodulated and displayed by the radio controlled clock. The radio controlled clock will contain an accurate time base oscillator to maintain timekeeping if the radio signal is momentarily unavailable. Other radio controlled clocks use the time signals transmitted by dedicated transmitters in the [[Shortwave radio|shortwave]] bands. Systems using dedicated time signal stations can achieve accuracy of a few tens of milliseconds.

GPS satellite receivers also internally generate accurate time information from the satellite signals. Dedicated GPS timing receivers are accurate to better than 1&nbsp;microsecond; however, general-purpose or consumer grade GPS may have an offset of up to one second between the internally calculated time, which is much more accurate than 1 second, and the time displayed on the screen.

Other broadcast services may include timekeeping information of varying accuracy within their signals. Timepieces with [[Bluetooth]] radio support, ranging from watches with basic control of functionality via a [[mobile app]] to full [[smartwatch]]es obtain time information from a connected [[Mobile phone|phone]], with no need to receive time signal broadcasts.