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Topic: Clock synchronization

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	Incremental clock synchronization
		In this version of the clock synchronization problem, processors have access to local clocks, which run at the rate of real-time; some clock may be corrupted and read wrong values.
		The clocks are not initialized and processors need to adjust them to be as close as possible (using an additive adjustment factor).
		Incremental clock synchronization algorithm (by Hagit Attya) does not allow syncronization when number of messages sent by particular process is more than ~30% of number of processes.
	www.cs.technion.ac.il /~hagit/summer01/Clock/web/proj.html (1073 words)

	[No title] (Site not responding. Last check: 2007-11-04)
		Synchronization protocols are described in [3] and [12] and synchronization algorithms in [2], [5], [10] and [11].
		Such clocks are readily available in several models ranging in accuracies of a few hundred milliseconds to less than a Mills [Page 2] RFC 957 September 1985 Experiments in Network Clock Synchronization millisecond and are typically synchronized to special ground-based or satellite-based radio broadcasts.
		Synchronizing Network Clocks The algorithms described in the previous section are designed to achieve a high degree of accuracy and stability of the logical clocks in each participating host.
	www.ietf.org /rfc/rfc957.txt (8717 words)

	Clock synchronization - Wikipedia, the free encyclopedia
		Clock synchronization is a problem from computer science which deals with the idea that internal clocks of several computers may differ.
		Cristian's algorithm and the Berkeley Algorithm are some solutions to the clock synchronization problem in a centralized server environment.
		The most used clock synchronization solution on the internet is the Internet Network Time Protocol (NTP) which is a layered client-server architecture based on UDP message passing.
	en.wikipedia.org /wiki/Clock_synchronization (504 words)

	Executive Summary: Computer Network Time Synchronization
		Clock errors are due to variations in network delay and latencies in computer hardware and software (jitter), as well as clock oscillator instability (wander).
		By its very nature, clock synchronization is a continuous process, resulting in a sequence of measurements with each of possibly several servers and resulting in a clock adjustment.
		At the heart of the synchronization protocol is the algorithm used to adjust the system clock in accordance with the final adjustment determined by the data grooming algorithms.
	www.eecis.udel.edu /~mills/exec.html (2902 words)

	Synchronization - Wikipedia, the free encyclopedia
		Synchronization (or Sync) is a problem in timekeeping which requires the coordination of events to operate a system in unison.
		Synchronization is important in fields such as digital telephony, video and digital audio where streams of sampled data are manipulated.
		Automotive transmissions contain synchronizers which allow the toothed rotating parts (gears and splined shaft) to be brought to the same rotational velocity before engaging the teeth.
	en.wikipedia.org /wiki/Synchronization (637 words)

	Clock Synchronization
		To do this the clocks at the two ends of the path have to be synchronized.
		And the point of the twin story is that even if they are synchronized at one moment in the same frame, their subsequent travels over curved world lines (i.e.accelerations) will cause them to read differently when they are brought back together.
		Doesn't sending the original signal to reset the clocks assume that the speed of light in both directions is the same, and is not the same true of the first signal that you get from the clocks.
	www.physicsforums.com /showthread.php?t=53313 (584 words)

	Physics News Update 701
		Clock synchronization with entangled photons has been proposed as an idea and now demonstrated in an experiment.
		Modern clocks have improved to such a level that the resolution and accuracy of the comparison techniques have become the limiting factors to determine the degree of synchronization, t1-t2.
		The Maryland physicists (contact Alejandra Valencia, avalen1@umbc.edu) synchronized two distant clocks, each attached to a photodetector, by building up a statistical sampling of the clock responses, first sending a photon from one emerging beam to one detector while its mate went to the other detector, and then switching the entangled pairs to the opposite detectors.
	www.aip.org /pnu/2004/split/701-2.html (269 words)

	Digital Audio Synchronization
		All clocks in a system must be synchronized with one another.
		Since there can only be one master clock reference, you would most likely set the DAW to internal and the other two devices (slaves) to digital input.
		The clock signal is transmitted with 75-ohm coaxial cables with BNC connectors.
	www.mtsu.edu /~jakins/4200/4200clocking.html (424 words)

	A Theory of Clock Synchronization (abstract) (Site not responding. Last check: 2007-11-04)
		Synchronization graphs are derived from information which is locally available for computation at the processors (local time of events and system specification), and can therefore be used by distributed algorithms.
		Using synchronization graphs, we obtain the first optimal on-line distributed algorithms for external clock synchronization, where the task of all processors is to estimate the reading of the local clock of a distinguished processor.
		We also present results for internal synchronization, where the task of the processors in the system is to generate a synchronized ``tick.'' Our approach is robust in the sense it encompasses various system models, such as point-to-point or broadcast channels, communication links that may lose, duplicate and re-order messages, and crashing processors.
	www.ccs.neu.edu /home/boaz/thesis-abs.html (255 words)

	Introduction to Distributed Clock Synchronization and the IEEE 1588 Precision Time Protocol- Developer Zone - National ...
		To achieve this synchronization, devices in the system must either have direct access to timing signals from a common source, or the devices must synchronize their individual clocks in order share a common time base.
		A heterogeneous network of clocks is a network containing clocks of varying characteristics, such as the origin of a clock’s time source, and the stability of the clock's frequency.
		If the ‘grandmaster’ clock is removed from the network, or if its characteristics change in a way such that it is no longer the ‘best’ clock, the BMC algorithm provides a way for the participating clocks to automatically determine the current ‘best’ clock, which becomes the new grandmaster.
	zone.ni.com /devzone/cda/tut/p/id/2822 (2241 words)

	Metro Tel: CSC 100 Clock Synchronization Comparator
		The CSC-100 Clock Synchronization Comparator is a compact, handheld instrument that compares the clock signals from two different PCM sources, typically a DS1.
		Circular displays indicate the clock relationships in a familiar, analog style using an outer circle of 16 red LEDs and an inner circle of 12 green LEDs.
		The clocks are compared digitally on a cycle by cycle basis.
	www.metrotelcorp.com /csc100.html (374 words)

	Einstein's Clock Synchronization Convention (Site not responding. Last check: 2007-11-04)
		The primary reason to synchronize clocks is to be able to measure velocities.
		It is a matter of "convention" that one does not measure the velocity of an airplane by looking at the difference of the clocks at which it takes off in the PST timezone, and the clock at which it lands in the CST timezone.
		One insists that to get the "fair" speed of the airplane, one uses clocks that are synchronized according to a convention, using the same time-zone for both takeoff and landing times.
	www.physicsforums.com /showthread.php?t=86985 (2367 words)

	Self Winding Clock Synchronization (Site not responding. Last check: 2007-11-04)
		These synchronizing clocks can be identified by either "Naval Observatory Time Western Union" or "Synchronized Self Winding" written on the face or located on the case.
		Originally, these clocks were either local master clocks found in Western Union offices or secondary clocks, synchronized by the local master clock.
		The master clock was synchronized by a national clock in Washington using the Western Union telegraph lines.
	www.ubr.com /clocks/sync/syncwu.html (2503 words)

	Clock Synchronization (Site not responding. Last check: 2007-11-04)
		Clock synch and max error: It is proven in the paper that if P measures the round-trip time of the request/reply pair as 2D, the value displayed by Q's clock when it sends its reply is T, and the value displayed by Q's clock when P receives this reply is
		Obtaining a desired precision: The precision of the clock estimate is limited by the measured round-trip time of the reply/request pair.
		Because a master has a reliable clock source, the master can detect if its own clock as failed, and since masters update themselves more frequently than slaves, a slave can deduce its own clock has failed if such an erroneous condition occurs two times in a row without the master declaring itself invalid.
	swig.stanford.edu /pub/summaries/distribsys/prob_clock.html (468 words)

	Clock Synchronization Without Electromagnetic Signals
		The utilization of signals from events occurring at places removed from the clock is a pointless procedure, since one obtains thereby not the times of the events, but the arrival times of the corresponding signals at the location of the clock, a procedure fraught, obviously, with the unknown properties of the intervening space.
		True, the assumption is here implicit that all clocks, whatever their nature or construction, will record the same time at every point over the traversal (for example, any two or more different types of clocks, sent together over the path, would all show the same time at every point on the path).
		Clearly then, a clock moving with an object or mass-point in a physical process enjoys a privileged position with respect to specification of the process: it alone has an unambiguous temporal description of the process, which in the present case happens to be uniform motion relative to a given coordinate system F.
	www.fiu.edu /~hawkinsl/paper/synchronize2.htm (4317 words)

	Computer Clock Synchronization
		Once installed, you have the capability of updating your clock at regular intervals, and the most recent adjustment made to your clock is reported by the program reported to the nearest 1/100th of a second.
		NTPC keeps your PC clock in synchronization also includes a a server mode.
		TimeRC 2.0 sets the clock in your computer via SNTP and displays the adjustment to your clock to the closest 1/100th of a second.
	home.satx.rr.com /sfisher/clock.html (1499 words)

	Atomic Clock Synch, Atomic Clock Synchronization, Atomic Digital Clocks, Atomic Radio Controlled Clock, How An Atomic ...
		However if a problem with atomic clock synchronization is suspected, the clock should first be checked by using the NIST atomic clock on the internet or by listening to NIST radio station WWV using a shortwave radio or telephone (dial 303-499-7111).
		Not all atomic digital clocks have this feature and another time zone may have to be selected in order to make the clock display the correct time when DST is in effect.
		The clock might not have been properly aligned at the factory, or it might have been jostled during shipment, causing the hands to move.
	www.weathershack.com /education/atomic-clock-synch.html (831 words)

	Chameleon Clock OATS Edition
		Member firms may synchronize business clocks to any source that is accurate to within three seconds of the National Institute of Standards and Technology (NIST).
		To maintain clock synchronization, clocks should be re-synchronized, if necessary, at pre-determined intervals throughout the day.
		As the clock uses Winamp skins and bitmap digits for time and date display, you can choose any clock size and look you like.
	www.softshape.com /software/desktop/chamclock/oats (376 words)

	AudioRail Technologies (Site not responding. Last check: 2007-11-04)
		Sometimes limitations in the available clocking schemes of one product will limit the user's choices, such as when a device can only operate as a slave, or defaults to slave mode when another device is connected to it.
		The reason for the necessity of a common clock in any digital audio system is that no two independent clock sources can maintain perfect synchronization.
		When a device is configured as a "slave" it extracts the clock from the digital audio stream and locks onto it, instead of its own quartz crystal oscillator.
	audiorail.home.comcast.net /ar_word_clock.htm (621 words)

	SynchroTray Clock Notes (Site not responding. Last check: 2007-11-04)
		Some computers may have inaccurate and unreliable clock and that is the case when you may need to synchronize your clock more than once a day.
		During synchronization the program checks date setting of your system too and correct it if it is wrong.
		We have reset the clock on this machine daily and yet by the end of the day it always seems to end up 10 minutes slow.
	www.brigsoft.com /atomic-clock-sync/AtomicHelp.htm (1425 words)

	Atomic clock sync
		Synchronizing PC clock with atomic clock using official Sources of Time for the United States and other countries.
		Synchronization is done automatically while you are receiving your e-mail or surfing the web and no actions are to be done by you.
		Clock in your PC needs to be corrected only several times a month.
	brigsoft.com /atomic-clock-sync (1155 words)

	Clocks and Time: Time Software for PC personal computers for time setting and synchronization, clock rate correction ... (Site not responding. Last check: 2007-11-04)
		Because PC clocks rarely have a correct rate (they lose or gain time significantly) it is useful to correct the rate with software that determines the rate error and then periodically corrects the time.
		While plug-in GPS boards for time synchronization recently cost about $3000, GPS navigation receivers can be obtained for $300 or less, and it is anticipated that lower-cost time synchronization systems will become available.
		Clock synchronization is built into the Macintosh operating system since Mac OS 8.5, that came out around November 1998 (current is Mac OS 8.5.1).
	www.ubr.com /clocks/timesw/timesw.html (616 words)

	Atomic Clock Synchronization, Atomic Clock Synch, Radio Controlled Clock, Atomic Digital Clocks, How Does An Atomic ...
		A radio controlled clock sold in North America is permanently set to receive and process an atomic clock synchronization signal broadcast from WWVB in Boulder, Colorado.
		If it's a wall clock, try mounting it on a wall perpendicular to the one it is currently on (if it is on a north or south wall try an east or west wall).
		Atomic clocks have antennas that are directional and reception may be improved by turning the antenna to increase signal strength.
	www.weathershack.com /education/atomic-clock-synchronization.html (650 words)

	White Paper Downloads — Time Synchronization (Site not responding. Last check: 2007-11-04)
		Proper clock synchronization is critical to ensuring good performance, improving troubleshooting, and producing accurate call detail records (CDRs) for billing.
		As you read this, your network of workstations and servers, each with their own clock, are time stamping files, email, transactions, etc., all the while your server logs are recording every manner of transaction in the event you need that information.
		This is followed by an equation for clock drift that shows the how the calculation for modeling drift in networks was established.
	www.ntp-systems.com /info_white_papers.asp (1087 words)

	Embedded.com - Deploy VoIP at the source
		The end result is that the TDM clock of the PBX at the customer premise is synchronized to the network master clock.
		This synchronization mechanism does not exist in packet networks, nor is there any network reference available to support TDM-emulated service, or to synchronize the various TDM equipment connected to the packet network.
		To resolve this situation and provide a synchronization mechanism for TDM equipment inside and outside the customer premises, it is necessary to implement one of several timing schemes.
	www.embedded.com /showArticle.jhtml?articleID=190302342 (1227 words)

	Clock Synchronization (NTP) Tests
		For the clock synchronization tests, an NTP server has been ported to the UoSat-12 spacecraft.
		Later in the test, a command is sent to the spacecraft to manually set the onboard clock in error by a large amount (2 - 3 seconds).
		The pass began with a spacecraft clock offset from UTC of approximately -300 mS.
	ipinspace.gsfc.nasa.gov /UoSat-12/ntptest (569 words)

	The CNS Clock (Site not responding. Last check: 2007-11-04)
		The CNS Clock is a GPS clock with high accuracy one-pulse-per-second outputs and software that manages the clock and keeps your computer's time synchronized to GPS.
		The CNS Clock is available in a rack mount version that allows up to three clocks per 3.5 inch panel.
		The connector on the rear panel of the CNS Clock is an isolated BNC with the emitter of U3 connected to the outer shell and the collector connected to the center pin.
	www.cnssys.com /cnsclock/CnsClock.html (1302 words)

	Clock (Synchronization)
		There is always at least one clock object available: the system real-time clock.
		For clocks that do not measure calendar time this absolute time may not represent a wall clock time.
		is not available and it is larger than the minimum resolution, then the clock will be set to the closest resolution that the clock supports, via truncation.
	www.rtsj.org /specjavadoc/javax/realtime/Clock.html (395 words)

	GPS Clocks for Computer Time Synchronization (Site not responding. Last check: 2007-11-04)
		For example, a computer with a GPS clock can provide synchronization for several servers which in turn provide synchronization to thousands of client computers.
		If your GPS clock suddenly goes haywire, NTPD is smart enough to know not to listen to it.
		Unfortunately, accurate clock synchronization is not possible on Windows 95 or 98 -- you can only synchronize them to about a half a second and only by a series of clock jumps.
	www.gpsclock.com /gps/g4.html (397 words)

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