DBS 毒鸡蛋事件发酵 市长救火严重烧伤

Ever wondered why we have satellite television? I know I have, particularly when we already have terrestrial or broadcast television available. They both seem very similar, the only difference being that with satellite you get lots more choice of channel. Of course there is cable television too, a fierce competitor for both services, but in this article I am going to stick to satellite television. Sattelite television really becomes important in areas where it is not possible to install cable and the broadcast television reception is poor. Both systems use radio wave signals to transmit and the waves travel in straight lines. That means for broadcast television, which is transmitted and received via land-based antenna, that the natural curvature of the earth will eventually break the signals’ line of sight. It also means that other land based signals and obstructions are likely to interfere with the TV signal and cause some distortion. Satellites that transmit TV are placed in orbit over 22,000 miles above the Earth and they rotate around the planet once every 24 hours and in the same direction that the Earth is rotating in. Because the Earth rotates once every 24 hours and the satellite moves around the Earth at the same velocity in the same direction, the satellite always stays over the same point on the surface. The satellites are said to be in geostationary orbit. Because they are high in the sky a satellite beams signals over a wide area of the planets surface. The satellites are also in communication with each other so that they can relay the same broadcast to all satellites in orbit over different parts of the world. This is how we are able to get TV live from anywhere on the Earth and view it at the same time as everyone else on the planet receiving a signal from a satellite. When you think about it it’s a pretty amazing feat of technology. When satellite television was first available the dishes needed to receive the signal were very expensive and people would set them up to receive programmes that were not really intended for everyone’s eyes. Nowadays people typically subscribe to a ‘Direct Broadcast Satellite’ (DBS) provider such as Dish Network or DirecTV in the US and Sky in the UK. These providers are able to select channels and broadcast them to people in the form of packages, for example the ‘Family’, ‘Movie’ or ‘Sports’ packages. The price depends on which packages you choose to subscribe to. To enable the whole system to make money for the organisations involved in the provision of satellite television, three techniques are commonly employed: Showing Adverts Advertisers pay to have their promotional material shown during the transmission. They generally pay more to have their adverts shown at peak times. I don’t know anyone who likes to have the advertisements distract their entertainment but it does pay for part of it. Regular Subscriptions Payment of a monthly fee for the privilege of being able to view encrypted channels. For your subscription you generally get a smart card that is loaded with the decryption keys and inserted into your receiver equipment. Licence Fee If you are in the UK and you have equipment that is capable of receiving TV signals then the law states you must pay for a TV licence. Note that you don’t have to use the equipment; you just have to possess it. The money from the licence fee goes to pay for the British Broadcasting Company or BBC and in return we don’t see any advertising or encryption on any BBC channels. This was a good idea in the early days of radio and TV and it helped to produce and maintain high standards of broadcasting all over the world. My personal opinion now however is that the licence fee is nothing more than yet another tax that we have to pay and I feel that the BBC should begin to stand on it’s own two feet. I doubt that it will happen anytime soon though. If a broadcaster uses only advertising to pay for their service then you may receive and view the signals without payment or subscription. If you live in the UK you still have to pay the licence fee though. There are five main components required to make this whole system work. To get the programmes from the producers to the end customer they must all be in place and they must all be working properly. It’s surprising how it works at all. Programmes are distributed by the DBS provider but not created by them. They stand in the middle between the consumer and the programme makers. Satellite Television Provider Signals from the broadcast sources are received by the provider and then transmitted to the network of orbiting satellites. Satellites The signals are received by the satellite network and retransmitted back to Earth. Receiving equipment The equipment normally provided by the DBS, allowing you to receive the signal from the satellite. A dish must be installed professionally somewhere on your property. Decoding and viewing A box near your TV will take the signal received and decode your chosen channels into a form that you can watch. So, there is a lot more to satellite TV than meets the eye but it provides us with high quality television, which is available almost everywhere on the earth. We have come a long way in a very short time with television. 相关的主题文章: