question: How do cars and computers know what time it is even after being completly without electricity or internet?
comment: The short answer is that they are never without electricity. In a computer, there is a tiny battery, often a CR2032 button cell, that keeps a chip running called the RTC, or Real Time Clock chip. Inside this chip there are several different components, a crystal and a clock chip. The quartz crystal is what actually keeps the time. Basically, when you apply a signal to it, it vibrates at a predetermined frequency, normally in the MHz range. This vibration is extremely consistent, and generally stays the same regardless of temperature or other factors. This vibration produces pulses at that frequency that are then read by the clock chip. The clock chip then uses that frequency as a reference to count the seconds. For example, if you had a 20 MHz crystal, that means it vibrates at 20,000,000 times a second. The clock chip would count the pulses from 1 to 20,000,000, and then advance the second counter. This entire circuit uses a minuscule amount of power, so oftentimes that tiny little battery will power it for years. Your car works exactly the same way, except that instead of a tiny little button cell battery, it is powered off of your car battery. That is why when your car battery goes completely dead, you have to reset your clock. Also, when you see a digital watch or clock that says "Quartz Movement" or something of the sort, it is referring to the quartz crystal that was mentioned above. & #x200B;
passages: Electronic time clock machines are manufactured in many designs by companies in China and sold under various brand names in places around the world, with accompanying software to extract the data from a single time clock machine, or several machines, and process the data into reports. In most cases local suppliers offer technical support and in some cases installation services.
   RTCs often have an alternate source of power, so they can continue to keep time while the primary source of power is off or unavailable. This alternate source of power is normally a lithium battery in older systems, but some newer systems use a supercapacitor, because they are rechargeable and can be soldered. The alternate power source can also supply power to battery backed RAM.
  
  Section::::Timing.
   To reduce the problem, many devices designed to operate on household electricity incorporate a battery backup to maintain the time during power outages and during times of disconnection from the power supply. More recently, some devices incorporate a method for automatically setting the time, such as using a broadcast radio time signal from an atomic clock, getting the time from an existing satellite television or computer connection, or by being set at the factory and then maintaining the time from then on with a quartz movement powered by an internal rechargeable battery.
   With current technology, most modern computers keep track of local civil time, as do many other household and personal devices such as VCRs, DVRs, cable TV receivers, PDAs, pagers, cell phones, fax machines, telephone answering machines, cameras, camcorders, central air conditioners, and microwave ovens.
   A GPS receiver can shorten its startup time by comparing the current time, according to its RTC, with the time at which it last had a valid signal. If it has been less than a few hours, then the previous ephemeris is still usable.
  
  Section::::Power source.
   Some microcontrollers have a real-time clock built in, generally only the ones with many other features and peripherals.
  
  Section::::Examples.:Radio-based RTCs.
  
  Some modern computers receive clock information by digital radio and use it to promote time-standards. There are two common methods: Most cell phone protocols (e.g. LTE) directly provide the current local time. If an internet radio is available, a computer may use the network time protocol. Computers used as local time servers occasionally use GPS or ultra-low frequency radio transmissions broadcast by a national standards organization (i.e. a radio clock).
  
  Section::::Examples.:Historic RTCs.
   Most digital clocks use electronic mechanisms and LCD, LED, or VFD displays; many other display technologies are used as well (cathode ray tubes, nixie tubes, etc.). After a reset, battery change or power failure, these clocks without a backup battery or capacitor either start counting from 12:00, or stay at 12:00, often with blinking digits indicating that the time needs to be set. Some newer clocks will reset themselves based on radio or Internet time servers that are tuned to national atomic clocks. Since the advent of digital clocks in the 1960s, the use of analog clocks has declined significantly.
   More recently, time clocks have started to adopt technology commonly seen in phones and tablets – called 'Smartclocks'. The "state of the art" smartclocks come with multi-touch screens, full color displays, real time monitoring for problems, wireless networking and over the air updates. Some of the smartclocks use front-facing cameras to capture employee clock-ins to deter "buddy clocking", a problem usually requiring expensive biometric clocks. With the increasing popularity of cloud-based software, some of the newer time clocks are built to work seamlessly with the cloud.
  
  Section::::Types.
  
  Section::::Types.:Basic time clock.
   Some cities have gone to a device called a Parkulator, in which the users purchase a display device, usually for $5 or $10, then load it with as much time as they care to purchase. They then activate the device when they park at a location, and place the display device on their dashboard so it is visible from the front windshield. The device counts down the time remaining on the device while it remains activated. When they return, then the clock stops running, and the person does not overpay for time unused. In the UK, it is now possible to park and pay with credit or debit card through a dedicated telephone service. Civil Enforcement Officers that patrol the parking area are automatically informed through their handheld devices.
   BULLET::::- 7,362,263 Keeping accurate time for a hybrid GPS receiver and mobile phone when powered off
  
  BULLET::::- 7,450,062 Keeping accurate time for a hybrid GPS receiver and mobile phone when powered off
  
  BULLET::::- 7,592,951 Device and method for minimizing the number of crystal oscillators used in an integrated navigation receiver and cell phone
  
  BULLET::::- 7,598,909 Keeping accurate time for a hybrid GPS receiver and mobile phone when powered off
  
  Measurement instruments
  
  BULLET::::- 3,609,326 Counting apparatus and method using separate counters for reference and unknown signal
   In general, modern watches often display the day, date, month and year. For mechanical watches, various extra features called "complications", such as moon-phase displays and the different types of tourbillon, are sometimes included. Most electronic quartz watches, on the other hand, include time-related features such as timers, chronographs and alarm functions. Furthermore, some modern smartwatches even incorporate calculators, GPS and Bluetooth technology or have heart-rate monitoring capabilities, and some of them use radio clock technology to regularly correct the time.
   BULLET::::- "Synchronous clocks" rely on the 50 or 60 Hz utility frequency of the AC electric power grid as a timing source, by driving the clock gears with a synchronous motor. They essentially count cycles of the power supply. While the actual frequency may vary with loading on the grid, the total number of cycles per 24 hours is maintained rigorously constant, so that these clocks can keep time accurately for long periods, barring power cuts; over months they are more accurate than a typical quartz clock. This was the most common type of clock from the 1930s but has now been mostly replaced by quartz clocks.
   BULLET::::- Computer real time clocks keep time with a quartz crystal, but can be periodically (usually weekly) synchronized over the Internet to atomic clocks (UTC), using the Network Time Protocol (NTP). Sometimes computers on a local area network (LAN) get their time from a single local server which is maintained accurately.
  
  BULLET::::- Radio clocks keep time with a quartz crystal, but are periodically synchronized to time signals transmitted from dedicated standard time radio stations or satellite navigation signals, which are set by atomic clocks.
  
  Section::::Operation.:Controller.
   With the mass market proliferation of mobile devices (smart phones, handheld devices), new types of self-calculating time tracking systems have been invented which allow a mobile workforce – such as painting companies or construction companies - to track employees 'on' and 'off' hours. This is generally accomplished through either a mobile application, or an IVR based phone call in system. Using a mobile device allows enterprises to better validate that their employees or suppliers are physically 'clocking in' at a specific location using the GPS functionality of a mobile phone for extra validation.
  
  Section::::Biometrics.
   A software-based clock must be set each time its computer is turned on. Originally this was done by computer operators. When the Internet became commonplace, network time protocols were used to automatically set clocks of this type.
  
  In Europe, North America and some other grids, this RTC works because the frequency of the AC mains is adjusted to have a long-term frequency accuracy as good as the national standard clocks. That is, in those grids this RTC is superior to quartz clocks and less costly. 
   Today, GPS navigation radio signals are used to precisely distribute time signals over much of the world. There are many commercially available radio controlled clocks available to accurately indicate the local time, both for business and residential use. Computers often set their time from an Internet atomic clock source. Where this is not available, a locally connected GPS receiver can precisely set the time using one of several software applications.
  
  Section::::Audible and visible time signals.
   The time reference used by a time server could be another time server on the network or the Internet, a connected radio clock or an atomic clock. The most common true time source is a GPS or GPS master clock. Time servers are sometimes multi-purpose network servers, dedicated network servers, or dedicated devices. All a dedicated time server does is provide accurate time.
   Consider two radio transmitters located at a distance of from each other, which means the radio signal from one will take 1 millisecond to reach the other. One of these stations is equipped with an electronic clock that periodically sends out a trigger signal. When the signal is sent, this station, the "master", sends out its transmission. 1 ms later that signal arrives at the second station, the "slave". This station is equipped with a receiver, and when it sees the signal from the master arrive, it triggers its own transmitter. This ensures that the master and slave send out signals precisely 1 ms apart, without the slave needing to have an accurate timer of its own. In practice, a fixed time is added to account for delays in the electronics.
   The Apple M7, M8, M9, M10, M11, and M12 coprocessors collect, process, and store sensor data even if the device is asleep, and applications can retrieve data when the device is powered up again. This reduces power draw of the device and saves battery life. In addition to servicing the accelerometer, gyroscope, compass, and in M8 and later coprocessors, barometer, the M9 coprocessor can recognize Siri voice commands from the built in microphones of the device.
   In 2006 Clock Software started to expand to countries outside Bulgaria and opened offices in Romania (2007) and Croatia (2008). The first markets where their products were adopted were Romania, Macedonia and Croatia.
   Each sensor can be accessed independently at a specific interval. For example, wind speed may be sensed every minute during the day to arrive at an average, while the snow pillow may be accessed every 15 minutes for the accumulated total.
  
  System performance has increased over the years, mainly due to a better understanding of meteor burst communication characteristics and improved equipment. While a 95 percent response to a system-wide poll is the standard, over 99 percent is common.
  
  Section::::Data storage, management and accessibility.
   Commercial digital clocks are typically more reliable than consumer clocks. Multi-decade backup batteries can be used to maintain time during power loss.
  
  Section::::Uses of digital clocks.
   BULLET::::- Solar Powered: the advantage of some solar powered units is that they have much more power over their lifetime than battery powered units. This gives them the advantage of reporting their position and status much more often than battery units which need to conserve energy to extend their life. Some wireless solar-powered units, such as the RailRider can report more than 20,000 times per year and work indefinitely on solar power, eliminating the need to change batteries.
  
  BULLET::::- Battery powered: asset tracking devices often conserve battery life by reporting in less frequently than vehicle-powered counterparts.
   Because they run on electricity, digital clocks often need to be reset whenever the power is cut off, even for a very brief period of time. This is a particular problem with alarm clocks that have no "battery" backup, because a power outage during the night usually prevents the clock from triggering the alarm in the morning. 
   Many integrated circuit manufacturers make RTCs, including Epson, Intersil, IDT, Maxim, NXP Semiconductors, Texas Instruments, STMicroelectronics and Ricoh. A common RTC used in single-board computers is the Maxim Integrated DS1307.
  
  The RTC was introduced to PC compatibles by the IBM PC/AT in 1984, which used a Motorola MC146818 RTC. Later, Dallas Semiconductor made compatible RTCs, which were often used in older personal computers, and are easily found on motherboards because of their distinctive black battery cap and silkscreened logo.
  
  In newer systems, the RTC is integrated into the southbridge chip.
  
presuppositions: There are times when cars and computers are completely without electricity. Computers do not have a power source when they are unplugged.
corrections: Car and computer batteries are still active and can tell time even when the car or computer is off. Computers have small batteries that keep time when they are unplugged.
raw_presuppositions: There are times when cars and computers are completely without electricity. Computers do not have a power source when they are unplugged.
raw_corrections: Car and computer batteries are still active and can tell time even when the car or computer is off. Computers have small batteries that keep time when they are unplugged.