Aanbieding van de dag: ringtone
Mobiele Telefonie
Alle informatie verzameld
Hoe werkt de mobiele telefonie eigenlijk?
Ik bel de hele dag door en zelfs met mensen aan de andere kant van de wereld. Geen idee hoe dit werkt eigenlijk. Ik bel gewoon. Best bizar eigenlijk, ik kan bellen met wie ik wil, waar dan ook, zolang ik zijn of haar nummer maar heb. Maar hoe dit allemaal werkt, daar heb ik nooit over nagedacht.
We weten nu waar het idee van de telefoon vandaan is gekomen. In grote lijnen weten we uit het voorgaande onderwerp ook hoe de telefoon werkt. Van de mobiele telefoon weten we dit nog niet goed. Vandaar dat we nu eens gaan kijken hoe de mobiele telefoon eigenlijk werkt.
Omzetten van de trilling
Op het moment dat je spreekt in de microfoon van een mobiele telefoon, worden de luchttrillingen omgezet in elektromagnetische trillingen. Dit omdat luchttrillingen niet zo ver en zo snel kunnen reiken als elektromagnetische trillingen. Dit omzetten van een trilling gebeurt allemaal in je mobiele telefoon via je chip. Op het moment dat de luchttrilling omgezet is naar een elektromagnetische trilling, wordt dit analoge signaal omgezet in een digitaal signaal. Dit betekent dat de gehele trilling omgezet wordt in kleinere deeltjes.
Zie het maar als kleine elektrische pakketjes die samen één signaal vormen. Je kunt het vergelijken met het alfabet. De losse letters binnen een alfabet zijn niet veel waard, maar op het moment dat je ze combineert kun je ze ontcijferen. Zie het als een willekeurig woord dat wordt opgedeeld in losse letters, om zo te vervoeren. Want alle losse letters in de zak zijn makkelijker te vervoeren dan het hele woord al aan elkaar (bij wijze van spreken). Bij aankomst worden de letters weer samengevoegd waardoor het oorspronkelijke woord weer ontstaat.
Dit gebeurt ook met de trilling van jouw stem. Op het moment dat jouw stem (luchttrilling) wordt opgedeeld in kleine pakketjes wordt dit signaal doorgegeven via een frequentie door de lucht (net als bij radiofrequenties). Als dit signaal aankomt bij de andere mobiele telefoon, wordt het elektromagnetische signaal weer omgezet naar een analoog signaal. Het proces wordt nu omgekeerd. Dit signaal zorgt ervoor dat de speaker in de andere mobiel gaat trillen op de frequentie die jij zojuist hebt doorgegeven. Het analoge signaal wordt nu weer omgezet in een luchttrilling, dat ervoor zorgt dat de ander jou kan horen.
Als je wilt weten hoe dit in de praktijk gaat, kijk dan naar onderstaand filmpje:
Mar
12
Ralink and TrendChip to merge
Ralink Technology Corporation and TrendChip Technologies Corporation, both based in Taiwan, are to merge, creating a leading company in the global home networking and broadband access semiconductor markets. The merged company will be called Ralink Technology Corporation. Wireless chipset specialist Ralink, which has a development centre in California, as well as headquarters in Taiwan, provides 802.11n solutions to customers in the Americas, Europe, and Asia. Its products are found in all major Wi-Fi market segments including personal computers, broadband gateways, digital televisions, Blu-Ray players, web cameras, and IPTV set-top-boxes. Semiconductor supplier TrendChip, which is also headquartered in Taiwan, has development centres in China. Chris Kao, Chairman of Ralink Technology, said: “By combining Ralink and TrendChip into a single company, Ralink Technology Corporation will be positioned to drive the growth of high-performance yet cost-effective ‘triple play’ voice, video, and data services throughout the Networked Digital Home.” Shinjou Fang, Chairman of TrendChip Technologies will be CEO of Ralink Technology and Chris Kao will continue to serve as Chairman. Earlier this month Ralink announced that its 802.11n Plus Bluetooth Combo has completed Bluetooth 3.0 + HS qualification by the Bluetooth Qualification Board.
Mar
12
3D prices not too steep
Website: Rapid TV News Samsung’s latest range of TVs will go on sale in the US at the end of March. Indeed, some models are already available, and will be in key European markets very shortly. We know their prices, and the 3D sets will not be cheap. Samsung’s debut into the 3D set market is its range of UNC7000 models which are already being discounted by Amazon at around $2339 for the 46” model and $2969 for the 55” which suggests that buyers are paying just $250 extra over the ‘non-3D’ models. Broadcasting of any sort of 3D signals is still some months away, so Samsung has handily bundled in an offer which includes a Samsung 3D Blu-ray player and a pair of active shutter glasses. Panasonic has also released its 3D plans, using Best Buy in the US as its prime retailer and charging $2500 for a 50” set, or $2900 when a 3D Blu-ray player and glasses are included. In other words 3D prices, at least for US buyers, are not too outrageous, and significantly less than early HDTV models. And most analysts expect these introductory prices to quickly fall as quantities – and competition – increases.
Mar
12
SES Astra says HD quality suffers when bit-rate is cut
Website: Rapid TV News This time next week SES Astra will unveil its latest data as to the number of homes viewing one or other of its satellites. The numbers will be good, but the number of HD channels now being offered in Europe is near-spectacular. But Astra admits there are complaints about too many broadcasters cutting their data-rates, leading to softer HD images. Thomas Wrede, Astra’s VP/product management, said that Astra’s own HD portfolio now contains 112 channels out of a European total of 280. Moreover, that 280 is expected to grow to about 600 by 2013. Wrede said more channels will be added to the Astra offering within the next few weeks, leading to at least 20 new channels by year-end, and another 30 next year. And these predictions could easily be pessimistic. “Usually forecasts are relatively optimistic, but in terms of HD they have been eventually too pessimistic. “Even in 2008 we had already exceeded their forecasts and if you look at the end of the decade it is clear that HD will be mainstream.” He also urged broadcasters not to squeeze the bit-rate of their HD transmissions. “There is not sufficient HD native content and at some times of the day you see up-converted material, and that’s something I urge broadcasters to change.” Wrede said there were viewer complaints when broadcasters ran at a data-rate of less than 12 Mbps. “There is a well known relationship between the number of subscribers and the number of channels and we find this with each pay-TV operator,” said Wrede. However, not everyone is finding it easy to earn revenues from HD. “If you look at the business models you find it works well for pay-TV operators and the public broadcasters, but for the commercial broadcasters there is an issue, the means of financing the extra costs. “This is why in Germany for real free-to-air you only see the public broadcasters. “The private channels have had to encrypt and the majority of HD channels on our system come from pay-TV operators”.
Mar
12
LG offers 3D TV prices
LG is the next TV producer out of the trap to deliver details and prices of its range of 3D televisions, destined for the UK.
There will be a late launch for the LG LD920, as the company estimate this one will be ready for late summer.
However, the LG LX9900 3D TV will be on the shelves of local electrical retailers in May.
There will be two sizes, the 47 inch and a 55 inch.
Both come with a LED backlit flatscreen fully capable of delivering 1080p images and the TV is only 3.16 cm thick!
As for the cost, the LG LX9900 3D TV with a 47 inch screen will be priced between £2,500 and £3,000, while the 55 inch version will come with a price tag between £3,600 to $4,000.