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Topic: Plesiochronous

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	Phase optimization for data communication between plesiochronous time domains patent invention
		Reliable communication between the launch and capture elements 110, 112 driven by the plesiochronous launch and capture clocks 106, 108, therefore, is dependent upon the phase relationship between the relevant edges of the launch and capture clocks 106, 108.
		The launch and the capture clocks 106, 108 as presented to the clock input to the launch and capture elements 110, 112, respectively, are shown as plesiochronous clocks with a constant relative phase.
		Alternate apparatus' and methods to generate and adjust the phase of one plesiochronous clock relative to another are known and are not detailed in the present teachings.
	www.freshpatents.com /Phase-optimization-for-data-communication-between-plesiochronous-time-domains-dt20061026ptan20060242473.php (3757 words)

	Plesiochronous Digital Hierarchy - Open Encyclopedia (Site not responding. Last check: 2007-11-02)
		The Plesiochronous Digital Hierarchy (PDH) is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems.
		The term plesiochronous is derived from Greek plesio, meaning near, and chronos, time, and refers to the fact that PDH networks run in a state where different parts of the network are almost, but not quite perfectly, synchronised.
		In this case, the multiplexer signals to the receiving multiplexer that a bit is "missing".
	open-encyclopedia.com /PDH (580 words)

	Plesiochronous matching apparatus - Patent 4821227
		A plesiochronous matching apparatus has a redundant system including two equipments of the same structure, that is, an on-line equipment (the reference character thereof being accompanied by "a") and a non on-line equipment (the reference character thereof being accompanied by "b").
		A plesiochronous apparatus in accordance with claim 2 further comprising standby start detecting circuit means for detecting a change in a standby operation designating signal to generate a control signal for effecting said standby operating mode.
		Accordingly, the conventional plesiochronous matching apparatus has a disadvantage that if the non-on-line equipment (standby state equipment) is selected after detection of a trouble in the on-line equipment, the same data trouble as in the on-line equipment exists in the newly selected on-line equipment which has been a standby (non-on-line) equipment before the switching transition.
	www.freepatentsonline.com /4821227.html (5399 words)

	New techniques re-time data signals for plesiochronous communication (Site not responding. Last check: 2007-11-02)
		A system for high speed serial data to be transported in data communications from one node to another node asynchronously is used, where each local system or node is based on reference frequencies that are close, but not exactly the same as the system reference frequency.
		This is known as a plesiochronous system, wherein each local clock has small frequency differences of typically 100-200 ppm.
		To accommodate the differences in data periods due to the +/- 100ppm frequency differences, plesiochronous systems employ a technique known as "bit stuffing", where special bits are either added or deleted to adjust the rate of an incoming data stream to the frequency of the system receiving the data stream.
	www.commsdesign.com /printableArticle?articleID=12801881 (2395 words)

	Plesiochronous Digital Hierarchy article - Plesiochronous Digital Hierarchy telecommunications networks fibre optic ... (Site not responding. Last check: 2007-11-02)
		Plesiochronous Digital Hierarchy article - Plesiochronous Digital Hierarchy telecommunications networks fibre optic plesiochronous synchronised - What-Means.com
		Recently, telecommunications companies have been replacing their PDH equipment with SDH equipment capable of much higher transmission rates.
		Plesiochronous Digital Hierarchy article - Plesiochronous Digital Hierarchy definition - what means Plesiochronous Digital Hierarchy
	www.what-means.com /encyclopedia/PDH (604 words)

	[No title]
		The Plesiochronous Digital Hierarchy (PDH) is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems.
		The term plesiochronous is derived from Greek plesio, meaning near, and chronos, time, andrefers to the fact that PDH networks run in a state where different parts of the network are almost, but not quite perfectly, synchronised.
		Plesiochronous Digital Hierarchy (PDH) refers to the three, digital communication standards of the world which use point-to-point, 2-wire-pair links and are based on the fundamental concepts of Time Division Multiplexing (TDM).
	www.lycos.com /info/plesiochronous-digital-hierarchy.html (557 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		Plesiochronous networks allow for variation in local clock frequencies (a common problem when using quartz oscillators) by padding out lower bitrate signals until all signals achieve a common bitrate.
		The main advantage of plesiochronous digital hierarchy (PDH) networks is their robustness to variations in local clock frequencies.
		Plesiochronous hierarchies require a 'multiplexer mountain' in order to drop a 64kbit/s signal from a higher-order bitstream; to drop a 64kbit/s channel from a 140Mbit/s channel, four multiplexers are required and this limits the flexibility of any PDH network.
	www.eee.bham.ac.uk /woolleysi/video_on_demand/tran_01.htm (430 words)

	Synchronus Digital Hierarchy (Site not responding. Last check: 2007-11-02)
		The current plesiochronous digital hierachy (PDH) evolved in response to the demand for plain voice telephony (sometimes called POTS - plain Old Telephone Service) and as such is not ideally suited to the efficient delivery and management of high bandwidth connections.
		The problem of flexibility in a plesiochronous network is illustrated by considering what a network operator may need to do in order to be able to provide a business customer with a 2 Mbit\s leased line.
		The plesiochronous tributaries are mapped into the appropriate synchronous container, and a single column of nine bytes, known as the Path Overhead (POH), is added to form the relevant Virtual Container (VC).
	sdh.neostrada.pl /introduction.html (3777 words)

	Device for multiplexing N plesiochronous digital trains - Patent 4002844
		These trains are, indeed, generally only plesiochronous, that is, they have a same rated pulse rate but are controlled by independent clocks, which are not synchronized in relation to one another; their pulse rate cannot therefore be strictly equal.
		These plesiochronous trains are therefore synchronized, all being brought to a same pulse rate slightly more rapid than that which each of them can have.
		The invention is, of course, not limited to the particular application (multiplexing of four digital trains having 2.048 M bits/s) which it has been chosen to describe and applies more particularly to the multiplexing of a greater number of channels having a higher output rate.
	www.freepatentsonline.com /4002844.html (3410 words)

	Plesiochronous -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-02)
		The term plesiochronous is derived from the Greek plesio, meaning near, and chronos, time, and refers to the fact that plesiochronous systems run in a state where different parts of the system are almost, but not quite perfectly, (Click link for more info and facts about synchronised) synchronised.
		According to (Click link for more info and facts about ITU-T) ITU-T standards, corresponding signals are plesiochronous if their significant instants occur at nominally the same rate, with any variation in rate being constrained within specified limits.
		The most common example of a plesiochronous system design is the (Click link for more info and facts about Plesiochronous Digital Hierarchy) Plesiochronous Digital Hierarchy networking standard.
	www.absoluteastronomy.com /encyclopedia/p/pl/plesiochronous.htm (176 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		European Plesiochronous Digital Hierarchy (PDH) total 64 kb data 64 kb megabits level channels channels per second 1 E1 32 30 2.048 2 E2 132 120 8.448 3 E3 537 480 34.368 4 E4 2176 1920 139.264 Level 1 (E1) carrier uses 8,000 frames per second, with each frame containing 32 bytes.
		Plesiochronous Level-2 Level-2 signal at 8.448 Mbps consists of 9,962 frames per second, each with 848 bits.
		Designed to carry all the plesiochronous signals (DS-1, DS-3, PDH levels 1 to 4, etc.) Data (SPE or Synchronous Payload Envelope) is found using a pointer.
	www.cis.temple.edu /~stafford/thunder9899/sp99/week5/mux.txt (1881 words)

	RE: [PWE3] comments on draft-ietf-pwe3-requirements-03.txt
		Yaakov, There is a different between the classification of TDM circuits into plesiochronous digital hierarchy (PDH) and synchronous digital hierarchy and the actual synchronization architecture deployed in the network, or their internal multiplexing characteristics.
		E1 and T1 are referred in the ITU specs as belonging to the plesiochronous digital hierarchy (PDH).
		To understand the difference, you might note that plesiochronous synchronization is used in certain SDH deployments.
	www.ietf.org /mail-archive/web/pwot/current/msg03006.html (446 words)

	Areas of Unrest (Site not responding. Last check: 2007-11-02)
		"Plesiochronous" is used to refer to communications that are "close" in time.
		When you have a plesiochronous system, you have, say, two synchronous networks that need to interact, but each one uses a different master clock.
		Later in the day, I ran into Dave in the hall and he asked me how things were going and I just said "hectic." I should have said my life is plesiochronous.
	www.areasofunrest.net /40/20Aug99.html (697 words)

	OFC Communication
		This introduction of justification 'dummy' bits occurs at all levels of multiplexing in the hierarchy, and this plesiochronous (almost synchronous) mode of transmission multiplexing is termed Plesiochronous Digital Hierarchy (PDH).
		Plesiochronous Digital Hierarchy was intended as a solution for voice telephony channel multiplexing and is not suited for the high-bandwidth connections that the applications of today need.
		The plesiochronous signal is put in a container, along with 'dummy' bits, similar to actual plesiochronous multiplexing.
	msridhar.freeshell.org /ofc.htm (973 words)

	Plesiochronous Digital Hierarchy - Encyclopedia Glossary Meaning Explanation Plesiochronous Digital Hierarchy (Site not responding. Last check: 2007-11-02)
		Plesiochronous Digital Hierarchy - Encyclopedia Glossary Meaning Explanation Plesiochronous Digital Hierarchy.
		Here you will find more informations about Plesiochronous Digital Hierarchy.
		The orginal Plesiochronous Digital Hierarchy article can be editet
	www.encyclopedia-glossary.com /en/Plesiochronous-Digital-Hierarchy.html (641 words)

	Jeyatheepan Ulagapiragasam \| Net Home
		SDH (Synchronous Digital Hierarchy) is the next generation of transmission technology after plesiochronous era.
		SDH gas a well-defined interface to existing plesiochronous networks, which is the basic message of the multiplexing and mapping structure.
		In addition to being a solution that integrates to and can also grow with the plesiochronous networks where needed new SDH networks provide very high flexibility and improved management possibilities to meet the needs of the future.
	www.jeyatheepan.com /mtt/chapter4.htm (492 words)

	ATM Dictionary - Plesiochronous (Site not responding. Last check: 2007-11-02)
		Plesiochronous - Signals which are arbitrarily close in frequency to some defined precision.
		They are not sourced from the same clock and so, over the long term, will be skewed from each other.
		That same inaccuracy of timing will force a switch, over time, to repeat or delete frames (called frame slips) in order to handle buffer underflow or overflow.
	cell.onecall.net /cell-relay/FAQ/dictionary/plesiochronous.html (78 words)

	What is plesiochronous? - a definition from Whatis.com
		A plesiochronous system could arise as the result of two systems having slightly different clock readings over time.
		In such a system, one of the systems or a third system would need to notice the mismatch and make some compensating adjustment, such as repeating or deleting a data packet or frame.
		Plesiochronous can be compared with asynchronous, isochronous, and synchronous.
	searchnetworking.techtarget.com /sDefinition/0,,sid7_gci214373,00.html (257 words)

	ATM Dictionary - Plesiochronous (Site not responding. Last check: 2007-11-02)
		Plesiochronous - Signals which are arbitrarily close in frequency to some defined precision.
		They are not sourced from the same clock and so, over the long term, will be skewed from each other.
		That same inaccuracy of timing will force a switch, over time, to repeat or delete frames (called frame slips) in order to handle buffer underflow or overflow.
	www.cell-relay.com /cell-relay/FAQ/dictionary/plesiochronous.html (78 words)

	RE: [PWE3] comments on draft-ietf-pwe3-requirements-03.txt
		It does not matter > that in most > deployments they are not operated in a plesiochronous timing > architecture, or that they carry DS0 synchronously.
		E1/T1 must be synchronous to the nx64k clients they carry as there is no justification scheme that relates these 2 layer networks.
		> > 6019 plesiochronous > F: plésiochrone > S: plesiócrono > The essential characteristic of time-scales or signals such that their > corresponding significant instants occur at nominally the > same rate, any > variation in rate being constrained within specified limits.
	www.ietf.org /mail-archive/web/pwe3/current/msg03008.html (458 words)

	PLESIOCHRONOUS DIGITAL HIERARCHY digital
		Early core transmission facilities used frequency division multiplexing, but in the 1960s this system was largely replaced with the PDH (plesiochronous digital hierarchy), which is a system of multiplexing numerous individual channels into higher-level channels.
		These features were based on high-order multiplexing through a hierarchy of increasing bit rates up to 140 Mbps or 565 Mbps in Europe and had been defined in the late 1960s and early 1970s along with the introduction of digital transmission over coaxial cables.
		The multiplexing technique allowed for the combining of slightly nonsynchronous rates, referred to as plesiochronous, which lead to the term plesiochronous digital hierarchy (PDH).
	digilander.libero.it /a_digital/Plesiochronous_digital_hierarchy.html (591 words)

	principles of plesiochronous operation (Site not responding. Last check: 2007-11-02)
		The justification bits are recognize as such when demultiplexing occurs, and discarded, leaving the original signal.
		This process is know as plesiochronous operation, from Greek, meaning "almost synchronous".
		The use of plesiochronous operation throughout the hierarchy has led to adoption of the term "plesiochronous digital hierarchy", or PDH.
	www2.rad.com /networks/1994/sdh/doc32.htm (141 words)

	Re: [Asterisk-Dev] IAX2 trunk really should send timestamps as part of i
		Think plesiochronous :-) [if you don't know what that means, look it up].
		What goes into an IAX trunk packet is a bunch of plesiochronous streams.
		Think plesiochronous digital heirarchy :-) Because the streams are plesiochronous (unless one of the sources has a really screwy clock), you can just encode how much ahead or behind the group an individual stream is, which is a tiny value.
	www.mail-archive.com /asterisk-dev@lists.digium.com/msg08811.html (513 words)

	T1: A Survival Guide: Chapter 5: Timing, Clocking,and Synchronization in the T-carrier System (Site not responding. Last check: 2007-11-02)
		Having only one timing source did not fit into the model of the post-divestiture telecommunications landscape in the U.S. Plesiochronous networks are networks in which the elements are timed by separate clocks, which are very precise and operate within narrow tolerances.
		For contrast with a synchronous network, Figure 5-2 illustrates a plesiochronous network.
		In practice, though, the distinction between plesiochronous and synchronous is a hair-splitting one.
	www.oreilly.com /catalog/t1survival/chapter/ch05.html (2940 words)

	PDH - Plesiochronous Digital Hierarchy
		PDH is a acronym that can contains many meanings which are listed below.
		There may be many popular meanings for PDH with the most popular definition being that of Plesiochronous Digital Hierarchy
		If you have more information or know of another definition for PDH, please let us know so that we can review it and add that information to our database.
	www.auditmypc.com /acronym/PDH.asp (167 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		a reception processing means connected at an output of the reception multiplexer for transforming a plesiochronous signal into a synchronous signal for an SDH transmission channel;
		a transmission multiplexer, at the output of which a transmission processing means for transforming a transmitted synchronous signal into a plesiochronous signal is connected; and
		a desychronizer following the transmission processing means for recovery of transformed plesiochronous signal clocks of the transformed plesiochronous signals and to issue the transformed plesiochronous signals to a plurality of output channels.
	www.uspto.gov /web/patents/patog/week12/OG/html/1292-4/US06870856-20050322.html (153 words)

	Citations: A solution to a special case of the synchronization problem - Stewart, Ward (ResearchIndex) (Site not responding. Last check: 2007-11-02)
		extend the idea of synchronizer avoidance to cover plesiochronous timing, but do not address the issue of keeping data one for one while providing minimal latency.
		2: Plesiochronous Requirements A pleisochronous system is one where all the clocks operate at approximately the same frequency, f 0.
		6.2 Plesiochronous Requirements A pleisochronous system is one where all the clocks operate at approximately the same frequency, f 0....
	citeseer.ist.psu.edu /context/436810/0 (399 words)

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