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Topic: 4B5B

	4b5b Encodind (Site not responding. Last check: 2007-10-29)
		While this was of little concern in coaxial cable transmission, the limited bandwidth of necessitated a more efficient encoding method for 100 Mbps transmission using a 4b/5b MLT code.
		A 100 MHz data stream that uses a 4B/5B encoding therefore results in a125 MHz signal.
		However in Fast Ethernet, this 125 MHz signal is itself encoded as a mult-level signal using three signal levels (instead of the two levels used in Manchester encoding).
	www.erg.abdn.ac.uk /users/gorry/course/phy-pages/4b5b.html (0 words)

	4B5B at AllExperts
		Despite this 4B5B does not guarantee at least one transition for each bit period, however there are enough transistions to allow the clock signal to be recovered.
		The use of only 16 of the possible 32 groups of 5 bits means that 4B5B allows some errors to be detected as the error may change the group of 5 bits into one of the 16 unused and thus invalid combinations.
		Unfortunately the use of 5 bits to represent 4 bits does mean that the bandwidth needed to transmitted the data is increased by 25%.
	en.allexperts.com /e/0/4B5B.htm (260 words)

	4B/5B or 4B5B
		4B/5B, also called 4-byte/5-byte or 4B5B, is a block encoding scheme used to send Fast Ethernet data and for MADI (Multichannel Audio Digital Interface).
		Since there are 32 possible combinations of 5 bits and only 16 combinations of 4 bits the 16 groups of 5 bits with the most transitions in are used in order to provide as many transitions as possible.
		Despite this 4B5B does not guarantee at least one transition for each bit period, however there are enough transistions to allow the clock signal to be recovered.
	www.javvin.com /networkingterms/4B5B.html (123 words)

	Delay line separator for data bus - Patent 5412697
		The delay line separator of claim 4, wherein each of said delay means of said delay line provides a delay of approximately 10 nanoseconds, said pulses of said pulse signal have a width of approximately 10 nanoseconds, and said pulse stretchor increases said pulse width to approximately 20 nanoseconds.
		To decode the 4B5B packet to extract the transmitted data, a clock signal encoded within the data packet must first be extracted.
		These and other objects of the invention are achieved by a delay line separator for extracting a clock signal from a combined clock/data signal received along a serial data line with the combined signal including pulses bounded by signal level transitions of first and second types, such as rising and falling edges.
	www.freepatentsonline.com /5412697.html (7848 words)

	U.S. Patent: 6091348 - Circuit and method for on-the-fly bit detection and substitution - July 18, 2000
		A 4B5B block code encodes every four bits of a bit stream into five bits, chosen in order to reduce runs of consecutive 1s and 0s and thus prevent baseline wander problems.
		The programmable counter 220 may receive an input that determines what the prescribed number is and an input that resets the count, which allows the programmable counter 220 to conditionally produce a plurality of latch control signals during the reception of the bit stream.
		In the case of 4B5B block code decoding, programmable counter 220 is configured for generating a latch control signal after counting every five bit periods.
	www.everypatent.com /comp/pat6091348.html (3987 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal (Site not responding. Last check: 2007-10-29)
		4B5B works by mapping groups of four bits onto groups of 5 bits.
		Depending on the standard or specification of interest, there may be several 4b5b characters left unused.
		The presence of any of the "unused" characters in the data stream can be used as an indication that there is a fault somewhere in the link.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=4B5B (224 words)

	WildPackets - Signal Encoding - 4B/5B
		In order to send information using 4B5B encoding, the data byte to be sent is first broken into two nibbles.
		Hex E is remapped to the 4B5B code 11100.
		Unlike 4B5B, 8B6T completely prepares the data for transmission; no further encoding is required.
	www.wildpackets.com /support/compendium/fast_ethernet/signal_4b5b (0 words)

	Code 4B5B :: netzikon :: Netzwerklexikon
		Der Code 4B5B kodiert jeweils 4 Bits des Datenstromes in eine 5 Bit Kodierung.
		4B5B vermeidet lange Folgen von 1 oder 0.
		Auch bei langen Folgen von 1 oder 0 im Datenstrom, erzeugt 4B5B Bitwechsel.
	www.netzikon.net /lexikon/c/4b5b.html (0 words)

	Circuit Cellar - Digital Library - CCO
		This is done to prevent long strings of ones or zeros from being encoded, which contributes to loss of synchronization on the signal.
		In this technology, the 4B5B encoded data is transmitted using non-return-to-zero, invert-on-one (NRZI) signaling.
		A 4B5B data rate of 125 Mbps is obtained using a 62.5-MHz carrier.
	www.circuitcellar.com /library/ccofeature/antonakos0402/2.htm (692 words)

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