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- B - Y
- Blue minus luminance(Y). One of two color difference signals used in
encoding NTSC composite television
signals.
Backhaul
- Term used to describe the transmission of a signal (normally video) from
the end of a microwave or broadcast system to a central point.
Bandwidth
- A measure of the information carrying capacity of a communications
channel; the higher the bandwidth, the greater the amount of information
which can be carried. A range of frequencies available for signaling in a
communication channel.
Baseband
- The transmission of unmodulated signals, usually by direct current, over
short distances on a communication channel.
Basic Rate Interface (BRI)
- See ISDN.
Beam splitter- For tele- oto/ophthalmoscopes. Allows direct visualization through the
device into the eye or ear by the clinician, while still routing a portion
of the image to the video camera. This is usually preferred by the
clinician who is accustomed to looking directly through the device rather
than at a video monitor.
Bell System
- A group of affiliated RBOCs (Regional
Bell Operating Companies) in the USA which operate under consistent rules
and specifications, many of which are set by AT&T.
Bipolar with 8 Zeros Substitution (B8ZS).
- A method for 1's density control for bipolar transmission signals such
as T1.
Bit depth
- The number of colors or levels of gray scale a scanner or monitor
supports. An 8-bit scanner can differentiate between 256 (28)
levels of gray. A 12-bit scanner supports 212 = 4,096 levels of
gray.
Bit Error Rate (BER)
- Bit Error Rate, the absolute number of errors which may be present,
often experssed as xxE-y, where x is a floating point value and y is an
exponent. A measure of quality of digital transmission systems. Expresses
the ratio of correct bits to erroneous bits. To overcome transmission
errors, many codecs include forward error correction , important for
transmission of highly compressed data.
Bit Map
- Screen memory such that each pixel corresponds to one bit in memory for
monochrome screens or several bits for colour screens. Representation of
characters or graphics by individual pixels arranged in row (horizontal)
and column (vertical) order. Each pixel can be represented by one bit (simple
black and white) or up to 32 bits (high-definition color).
Bitmapped Graphics
- Images which are created with matrices of pixels, or dots. Also called
raster graphics.
Bit Specifications
- Number of colors or levels of gray that can be displayed at one time.
Controlled by the amount of memory in the computer's graphics controller
card. An 8-bit controller can display 256 colors or levels of gray; a
16-bit controller, 64,000 colors; a 24-bit controller, 16.8 million colors.
Bits Per Pixel (BPP)
- The number of bits used to represent the color value of each pixel in a
digitized image.
Bits Per Second (BPS)
- The number of binary digits transmitted per second in a data
communication system.
BITNET
- The acronym for Because It's Time Network, an international electronic
network. BITNET, privately owned by a consortium of U.S. colleges and
universities, has about 2,500 host computers located primarily at
universities.
Bit-rate Allocation Signal (BAS)
- In Rec. H.221 and T.120, a word within the frame structure used to
transmit commands, control and indication signals and capabilities.
Bose-Chaudhuri-Hocquenghem (BCH)
- A forward error correction technique with low-overhead, often used for
videoconferencing as in H.261.
BRA
- European term for BRI
Bridge
- Device used to interconnect three or more telecommunications channels
such as telephone lines, to permit simultaneous, two-way communication
among all points that have been interconnected.
Broadband
- Communications which are capable of carrying a wide range of frequencies.
Broadcast television, cable television, microwave, and satellite are
examples of broadband technologies. A facility or circuit that has
bandwidth in excess of that required for high grade voice communication.
Bursty data
- Short, intense transmissions of grouped, related information. Sometimes
called "boluses of data" by medical clinicians.
Bus
- A network of computer devices that are connected by a shared
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