Digital terrestrial television, DTT in code, often abbreviated as digital terrestrial television, terrestrial television is represented in digital form. From a In fact, technically, the television signal is electronic information and electronic information can be represented in either analog or digital form.
The representation is used for analogue terrestrial television. This is called terrestrial TV and analogue terrestrial TV, just for the type of representation used for electronic information, is opposed to digital terrestrial television.
In the comparison between the analogue and digital television channels, the analog signals are more susceptible to interference because the receiver has no way to distinguish a change in signal due to interference from a genuinely informative, conversely, the digital signal is inherently immune to interference as long as remain mild. While the analog signal degrades continuously and, although a highly disturbed, however, presents a content at least partly comprehensible to a human observer, the digital signal over a certain threshold of disorder becomes indecipherable and loses any value of information.
The main benefits from the introduction of DTT
are a greater number of programs available
• a better quality image / audio
• possibility of interactive programs
The main advantages of digital broadcasting are to improve spectral efficiency and the introduction Flexibility use of available bandwidth: with the possibility of using compression algorithms can be transmitted four digital channels in place of an analog from the equivalent quality. Broadcasters can also choose to use a certain amount of bandwidth to transmit high quality with few channels or many channels with a lower quality.
For example, if the bandwidth is 24 Mb / s can transmit four channels of 6 Mb / s each, or twelve channels of 2 Mb / s and obviously in the second case, the quality will be smaller. Channels can also be provided with different characteristics: it is possible to transmit both channels in high definition channels optimized for small screens of mobile phones.
should also be pointed out the possibility of transmitting isofrequency, a technique that was not possible to implement in analog television broadcasts. This technological evolution is used to send the same signal on the same frequency simultaneously from multiple transmitting sites. Although currently in Italy apparently has not yet been widely adopted because of the inability to find a single clear channel over a wide area (eg a region), it would be desirable to a future use in this sense is to free up channels for perspective of TV / radio unit. In fact, if for example a region of the same frequency were used, one might move without the need for retuning, and furthermore there is the possibility of providing the service even worse served as mountain areas, using small transmitters in isofrequency precisely.
analogue terrestrial television is the most common form of television in the world, received through the normal parabolic antennas. In
satellite television transition from analog television satellite digital satellite TV is now largely complete, this is because the satellite television has spread from a few years, only after the terrestrial television and cable television. In addition, the satellite television has always been closely linked to the pay-TV. Satellite television it can spread a number of channels much higher than the terrestrial television and cable television, this has always been chosen by the pay-television. And the satellite pay-TV are almost always been provided through a handset owner, often for hire, then, if the pay-TV transition from analog television to satellite television digital satellite receiver is replaced by the same pay-TV no additional cost to the user.
Cable television has followed a similar trend in that, even if it has spread many years before satellite television, has always been tied to the formula pay-TV.
The speech is instead completely different to the analogue terrestrial TV. First type of television to spread throughout the world, has always been the most popular type, mainly from the free television, especially on public television. In countries where public television has an important role in the transition from analog to digital need for users to acquire new equipment to continue to benefit from public service. For this reason, the transition from analogue terrestrial TV to digital terrestrial television will inevitably be slow, due to the normal replacement cycle of television sets, even if they are often planned by the governments of the Member deadlines for these transitions (often procrastinate).
According to recent EU regulations, EU member states converted or are converting their infrastructures for the spread of television channels, from analog to digital systems, the second time decided independently by the authorities of various countries.
decoder for digital terrestrial television manufactured by TeleSystem
Decoder for digital terrestrial TV with support for smart card
For normal viewers, the main disadvantage of digital terrestrial is the need to buy new equipment capable of its receipt. You can replace their televisions with new models capable of receiving independently or alongside the digital transmissions to televisions already owned the external receiver (decoder). In addition to a cost in economic terms this is a practical difficulty for people who, like many elderly, are not familiar with the technology: the use of a new television requires a change of habits and the use of a decoder also implies a remote control anymore.
addition to televisions, in general, any device to receive television channels such as VCRs and TV cards for computers, must have an external receiver or be replaced. TV and VCR can share a single decoder, but this causes a program to record while watching another on television is not possible.
Typical antenna to receive television channels
The antenna system required by the DTT is the same as that used for analogue transmissions and therefore already present in all homes, and some plants, particularly older, they may require a review.
also can not receive digital terrestrial signal with antennas that receive little signal for example, those v-shaped antennas that we all know dates as a tribute to analog television, mostly 14 inches, or purchased for a few euro as if it amplifies a poor analog signal you get an analog signal but acceptable If you amplify a little digital signal is obtained only low signal than before.
The use of external receivers leads to an increase in consumption of electricity: if a TV tuner is integrated into a television turning off the TV also implies the full shutdown of the tuner, however this does not happen if the tuner is external (ie if you use a decoder). Not only can it be easy to forget on the decoder, we must also consider that it is not completely off unless you unplug the plug, this behavior is dictated by reasons of convenience: the decoder thus remaining in a state of stand-by can keep some active components and to allow re-ignition by remote control. While consumption may decrease when a decoder is idle, it is equally true that there is zero: while the best performing devices exhibit lower consumption in watts, the cheapest ones can eat 5 or more watts. For a hypothetical household with two decoders, this means a consumption of 87.6 kWh / year (about 20 € / year at the rates typical), taking into mind the large number of people who have or will equip decoder is obtained that the amount of electricity wasted in Italy is of the order of one megawatt.
This problem will disappear as they technological obsolescence will encourage users to replace old TVs with new digital televisions with built-in decoder which then will make unnecessary the presence of the external decoder.
Since the infrastructure for digital terrestrial being built, the land cover may not be complete and reliable. In Italy, for example, it is far from complete and many areas are subject to temporary losses of signal reception or corrupt, especially in case of rain. These issues are clearly receiving expected to disappear with time.
