Tech Glossary:
Mostly abreviations and acronyms:
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2B1Q 2 Binary 1 Quaternary; The predominant signalling protocal used over an ISDNline is called 2B1Q. This is a four level line code associating a pair of bits with a single quarternary symbol (quat). Simply stated, the 2B1Q protocal represents four voltage levels: +3v, +1v, -1v and -3v. ISDN allows for the "bonding" of the B Channels into one circuit which provides a full 128 kbs channel suitable for high speed data transmission, Desk-top Video Conferencing, etc..

3:2 Pull-down: Method used to map the 24 fps of film onto the 30 fps (60 fields) of 525-line TV, so that one film frame occupies three TV fields, the next two, etc. It means the two fields of every other TV frame come from different film frames making operations such as rotoscoping impossible, and requiring care in editing. The 3:2 sequence repeats every five TV frames and four film frames, the latter identified as A-D, (see Film-to-TV Transfer). Only film frame A is fully on a TV frame and so exists at one timecode only, making it the editable point of the video sequence.

4:1:1: Composite Video Format; for every 4 units of luminance (Y: black-and-white) information, there are four units of "color-difference" information: 1 unit of luminance-red, (R-Y), and 1 unit of luminance-blue (B-Y).  This is a set of sampling frequencies in the ratio 4:1:1, used to digitize the luminance, Y, and color difference components R-Y, B-Y, of a video signal. The 4  represents 13.5 MHz, the sampling frequency of Y, and the 1s each 3.75 MHz for R-Y and B-Y (ie R-Y and B-Y are each sampled once for every four samples of Y).  With the color information sampled at half the rate of the 4:2:2 system, this is used as a more economic form of sampling where data video rates need to be reduced.  Both luminance and color difference are still sampled on every line but the latter has half the horizontal resolution of 4:2:2 while the vertical resolution of the color information is maintained.  (see also: 4:2:0, 4:2:2,Y, R-Y, B-Y and A:B:C notation)

4:2:0: A sampling system used to digitize the luminance and colour difference components (Y, R-Y, B-Y) of a video signal. The 4 represents the 13.5 MHz sampling frequency of Y while the R-Y and B-Y are sampled at 6.75 MHz - effectively between every other line only (ie one line is sampled at 4:0:0, luminance only, and the next at 4:2:2). This is used in 625 line systems where video data rate needs to be reduced. It decreases data by 25% against 4:2:2 sampling and the colour information has a reasonably even resolution in both the vertical and horizontal directions. 4:2:0 is widely used in MPEG-2 and 625 line Digital Video.  (see also, 4:1:1, 4:2:2, MPEG-2)

4:2:2: Composite Video Format; For every 4 units of luminance (black-and-white) information, there are four units of "color-difference" information: 2 units of luminance-red (R-Y), and 2 units of luminance-blue (B-Y). This provides better detail and color rendition than a standard composite output, which combines all the video information on a single wire. (see also, A:B:C notation)

10BaseT: A network capable of transmitting data at 10 Mb/s over twisted-pair wiring, specified by IEEE 802.3.

23B+D: The Primary Rate Interface (see PRI) of ISDN; 23 B channels and 1 D channel.

30B+D: The Euopean/Pacific Rim Primary Rate Interface (see PRI) of ISDN; 30 B channels and 1 D channel.

31B+D: The Euopean/Pacific Rim Primary Rate Interface of ISDN; 31 B channels and 1 D channel

100BaseFX: 2 fiber pairs

100BaseT: A network capable of transmitting data at 100 Mb/s, specified by IEEE 802.3.

100BaseT4: 4 pair type 3

100BaseTX: 2 pair type 5

100VG-AnyLAN: (IEEE 802.12)

802.1b: LAN/MAN Management, (IEEE Network Standard)

802.1d: LAN MAC Bridges, (IEEE Network Standard)

802.2: Logical Link Control Systems, (IEEE Network Standard)

802.3: LAN CSMA/CD (Ethernet), (IEEE Network Standard)

802.3a-z: Supplements to 802.3, (IEEE Network Standard). One supplement of particular note is 802.3z; Gigabit Ethernet.

802.4: Token Passing Bus, (IEEE Network Standard)

802.5x: Token Ring & Supplements, (IEEE Network Standard)

802.6: Distributed Queue Dual Bus, (DQDB), (IEEE MAN Networking Standard)

802.12: 100VG-AnyLAN, (IEEE Network Standard)

1394: IEEE 1394, also known as FireWire, Lynx, I-Link; see also IEEE 1394

2600: Hacker Magazine;;

Last Update:12/28/98
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