Analogical: Process allowing to restore way proportional or analogue an image or a sound, contrary with numerical which sample, graduates a sound or an image to be able to code it then.

Channel: A segment of the spectrum of 6MHz (larger of bandage) used for the terrestrial transmission (chains 2-69) or by cable, which an analogical program NTSC or one or more programs transmits numerical.

Coding convolute and punching: As the hertzian transmission channel is strongly a channel disturbed, it is advisable to still reinforce the protection measures of the data to transmit by the addition of a second error correcting code: the code convolute. The strong redundancy introduced by this code allows a errors correction effective, but it doubles the initial flow. In order to improve it output which 1/2 is, one will carry out an operation of punching in not transmitting all the bits at exit of the convolute coder with an aim of to reduce the redundancy of the code and the total flow.

COFDM(Coded Orthogonal Frequency Division Multiplexing): Multiplexing by division of coded orthogonal frequency. COFDM can simultaneously transmit several data flows, each one occupying only one small portion of the total bandwidth available. Its principal advantage is to make the echoes constructive, thus offering one reception without interferences, even under conditions of propagation difficult. It is the European standard TVN to which one preferred the 8-VSB in America.

Compression: Method of reduction of the number of bits necessary to record or transmit programs by removing them redundant data and/or data considered to be nonessential of the image and of its numerical. The standard of transmission of TVN in Canada uses video compression MPEG-2 and the code of audio compression AC-3. Compression the transmission of more than programs allows on only one channel.

Debit of transfer of the data: Speed transmission of the data expressed in "bits" by second(bps). Larger east speed, more data are transmitted, it who generally results in a better quality of image and sound. speed transmission of the video data is expressed in megabits by second(Mbps, 106) and that of the audio data in kilobits by second(kbps, 103).

DVB(Digital Video Broadcasting): Diffusion vidéo numérique. Name of the European project associating more than 180 structures (of the industrialists to the diffusers and the authorities of regulation) of more than 20 countries in Europe, which defined the standards of numerical diffusion Satellite (DVB-S), Cable (DVB-C) and Hertzian terrestrial (DVB-T). It also defined one system of encoding for the access control. Other standards DVB have also defined, like the DVB-TXT (teletext), DVB-ISC (services interactive) and DVB-MHP (driving of interactivity).

DVB-T : Video DIGITAL Broadcasting-Terrestrial, European standard for the multi-media diffusion of contents on equipment fixed (and portables under certain conditions).

Electromagnetic Spectrum (Spectre): Range of the frequencies of electromagnetic radiations, zero ad infinitum.

Filtering: Action to remove or attenuate certain frequencies of the spectrum, the light.

Frequency: A number of oscillations a second expressed in hertz characterizing an electromagnetic signal.

Hertzian (transmission): Transmission of the radio electric signals in the air.

Interlacing: This stage is intended to increase the effectiveness of the coding of Reed-Solomon. A code has one capacity of correction of packages of errors much lower than the capacity of correction of isolated errors. In order to make more effective the correction by coding Reed-Solomon, one disperses the errors by means of a interlace. With reception, the initial order of the samples is restored what causes of to divide the packages of errors into isolated errors and to facilitate the correction. Interlacing does not increase the capacity of correction but only sound effectiveness.

Jamming or interferences: Signals other than the received signal of the useful transmitter and which risk to disturb the reception of this last if they exceed a given threshold. This threshold depends on the channel on which jamming is received compared to the channel of useful signal and of the characteristics of the receiver. Jamming more known are those which arrive on the same channel as the useful signal (jamming Co-channel) and those which arrive on the adjacent channels (jamming channel adjacent).

Mixing: The flow of transport of entry MPEG-2 TS is organized out of packages fixed length of 188 bytes. Mixing is used for to carry out a dispersion of energy, i.e. a uniform distribution of energy in the channel of emission in order to avoid the long continuations of 1 or of 0 which would create parasitic lines in the spectrum of the signal and which would prevent the recovery of the clock.

Multiplexing of programs: Technique allowing to transport several programs in only one channel of television instead of only one diffused program, in the case of analogical television.

Musicam: Process of compression of the flow of sound data which eliminates certain no perceptible signals for the ear human.

Noise: Disturbance resulting in deterioration of the density of the blacks and the colours. The interference can to intensify until the appearance of the points white (snow).

QAM(Quadrature Amplitude Modulation, Amplitude modulation in squaring): Technique of modulation which modifies the amplitude of two carrying of the same frequency, out of phase of 90 degrees or in quarter of cycle, in two distinct signals which will borrow two ways different.

QPSK(Quadrature Phase Keying Shift): Phase modulation in four states.

Reed Solomon (Code): Algorithme mathématique de détection, correction ou compensation des bits erronés dans un message numérique. This code of the type CRC (code with cyclic redundancy) is used in the majority of the systems and numerical equipment.

Spectrum of frequencies: The spectrum frequency is defined by the whole of the frequencies used or usable by the radio waves. According to their frequency, waves radio electric present particular properties. This is why it frequency spectrum was cut out in bands in which one can to consider that the properties remain relatively homogeneous. Frequencies used for the diffusion TV are located in the bands metric (VHF, wavelength of 10 m with 1 m, frequencies of 30 MHz to 300 MHz) and especially decimetre (UHF, wavelength of 1 m to 10 cm, frequencies of 300 MHz with 3 000 MHz).

TNT: Terrestrial Numerical television indicates frequencies reserved for the networks of diffusion in DVB. The TNT will replace current analogical television gradually. Its offer of programs will be geared down, increasing, in the long term, the television capacity current to more than one about thirty chains.