GLOSSARY


A B C D E F G H I J K L M
N O P Q R S T U V W X Y Z

 
A

ASI:  stands for Asynchronous Serial Interface; describes an asynchronous transmission protocol which a start signal is sent prior to each code symbol and a stop signal is sent after each code symbol.

ASI-TS:  stands for Asynchronous Serial Interface Transport Stream; a transmission standard for DVB.

ATSC:  stands for Advanced Television System Committee. It is the name of the technical standard that defines the digital TV (DTV) that the FCC has chosen for terrestrial TV stations.  ATSC employs MPEF-2, a data compression standard.  This is the most common standard for digital cable TV systems and DBS systems in North America and East Asia.

 

C

CI:  stands for Common Interface; it is the slot on a digital television receiver into which a conditional access module (CAM) may be inserted for satellite television.  A receiver with a common interface allows the user to access encrypted television broadcasts as opposed to FTA channels.

COFDM:  stands for Coded Orthogonal Frequency Division Multiplexing. It is a complex modulation technique for transmission based upon the idea of frequency-division multiplexing (FDM) where each frequency channel is modulated with a simpler modulation.  COFDM is now widely used in Europe and elsewhere for terrestrial digital TV using the DVB-T standard. One of the major benefits provided by COFDM is that it renders radio broadcasts relatively immune to multipath distortion, and signal fading due to atmospheric conditions, or passing aircraft.

 

D

Decoder
:  a device that undo the encoding so that the original information can be retrieved. In digital electronics this would mean that a decoder is a multiple-input, multiple-output logic circuit that converts coded inputs into coded outputs, where the input and output codes are different.

Demodulator:  an electric circuit used to recover the information content from the carrier wave of a signal.

DVB:  stands for Digital Video Broadcasting; it is the internationally accepted, open standards for digital television.

DVB-C:  the DVB system's distribution of data by cable.

DVB-H:  the DVB system's distribution of data by terrestrial television for handhelds.

DVB-S:  the DVB system's distribution of data by satellite.

DVB-SI:  DVB-Service Information;  links various elementary streams into coherent programs and provides human readable descriptions for electronic program guides.

DVB-T:  the DVB system's distribution of data by terrestrial television.

 

E

Encoder
:  a device used to change a signal or data into a code.

 

M

MPEG-2
:  It is the designation for a group of coding and compression standards for Audio and Video (AV), agreed upon by MPEG (Moving Picture Experts Group). It is typically used to encode audio and video for broadcast signals, including direct broadcast satellite and cable TV.

Modulator:  the process of varying a carrier signal in order to use that signal to convey information. Why modulate?  1) to make the signal available for different users to share.  2) make the signal properties physically compatible with the propagation medium.

Multiplexing:  a.k.a. MUXing; a term used in electrical to refer to a process where multiple sources of information are combined in order to ease the organization, conversion, and transportation of the material from one place to another; multiple inputs are combined and released as one output.

 

Q

QAM
:  stands for Quardrature Amplitude Modulation; it is a method of combining two-amplitude-modulated signals into a signal channel, thereby doubling the effective bandwidtth. This is the standard used by DVB-C.

QPSK:  stands for Quardrature Phase Shift Keying, it is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave). This is the standard used by DVB-S.

 

R

Re-multiplexer
:  a device that combines many transport stream inputs into one transport stream output.

 

S

SPI
:  stands for Synchronous Parallel Interface, a standard for data interface, implemented by DVB as well.