Advantech SBD75e Series, Инструкция по установке и эксплуатации

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Glossary
Term Description
BPSK Binary Phase Shift Keying: A modulation technique used to
communicate data over long distances by altering the phase of a
carrier signal according to the data binary states. The simplest form of
phase shift keying, it uses two phases which are separated by 180° and
so can also be termed 2-PSK. Sometimes called PRK, Phase Reversal
Keying.
BW Bandwidth: The transmission capacity of an electronic line such as
(among others) a communications network, computer bus, or broadcast
link. It is expressed in bits per second, bytes per second or in Hertz (cycles
per second). When expressed in Hertz, the frequency may be a greater
number than the actual bits per second, because the bandwidth is the
difference between the lowest and highest frequencies transmitted. High
bandwidth allows fast transmission or high-volume transmission.
CA Conditional Access: The technology used to control the access to
viewing services to authorised subscribers through the transmission of
encrypted signals and the programmable regulation of their decryption
by a system such as viewing cards.
C-Band The portion of the electromagnetic spectrum, which spans the
frequency range of approximately 5.250-5.925 GHz (as defined by the
ITU). Used by communications satellites and preferred in tropical climates
because it is not susceptible to fading.
CRC Cyclic Redundancy Check: An error-detecting code use to check the
accuracy of transmitted, or stored, data. An algorithm computes a
numerical value based on the data bits in a block of data. This number is
then added to the block of data as check bits and transmitted across
the link. The receiver uses the check bits, and the same algorithm, to
check the accuracy of the received data by comparing the results of
the algorithm and the data received. If a mismatch occurs, an error in
transmission is presumed.
dB Decibels: A ratio of one quantity to another using logarithmic scales to
give results related to human aural or visual perception. dB is a ratio
whereas dBm, for example, is an absolute value, quoted as a ratio to a
fixed point of 0 dBm. 0 dBm is 1 mW at 1 kHz terminated in 600
Ω . 0 dBmV
is 1 mV terminated in 75 Ω .
DCE Data Communications Equipment: A classification of equipment used by
the RS-232 standard (and others) to identify equipment types and their
communications interface requirements. It establishes, maintains and
terminates a session on a network but is not the source (see DTE) or
destination (transmission circuit) of signals. A DCE device may typically
be a modem, a codec, or convert signals to comply with the
transmission path (network) format.
DCT Discrete Cosine Transform: A technique for expressing a waveform as a
weighted sum of cosines. Raw video data is not readily compressible.
DCT is not in itself a compression technique but is used to process the
video data so that it is compressible by an encoder. DCT processes the
picture on an 8x8-pixel block basis, converting the data from an
uncompressible X Y form (as displayed by an oscilloscope) to a
compressible frequency domain form (as displayed by a spectrum
analyser). Can be forward DCT or inverse DCT.
SBD75e Series Demodulator Installation and Operation Manual
B-3