Since 1990 the evolution of mobile phones has not known stop along with that of mobile telephony as an integrated communication system.
Mobile phone evolution
When mobile phones or cell phones were launched for the first time in the relatively distant 1990s they did not have the extremely small size that they now have combined with an insignificant weight.
At first they were large and heavy enough to carry around.
But in this field, electronics made great strides, passing in a few years from the old tacs network, based on an analog transmission system, to the much more performing digital gsm network first and umts later, with a considerable expansion of the technological possibilities offered, by the sending sms and mms messages first up to the possibility of video calling other users, watching television with video phones and surfing the internet with the latest generation smartphones.
The specific absorption rate or Sar is a value that indicates the level of power absorbed by radio frequencies by the human body when it is exposed for a longer or shorter time to an electromagnetic field.
The Sar unit of measurement is the Watt calculated per kilogram and is mainly used to measure the amount of radio frequencies emitted by a cell phone, as cell phone manufacturers are obliged to produce models capable of emitting only a limited level of radiation.
In countries belonging to the European Union the limit set for the Sar is 2 watts per kilogram calculated as an average under a thickness of ten grams of skin.
At lower values of Sar there is a lower heating of the tissues which guarantees a lower health risk.
A mobile phone purchase is a habit that has been established for years and involves more and more people.
When the first models came out in the second half of 1990, mobile phone prices were very high and, as the rechargeable formulas did not yet exist, he was forced to enter into a subscription contract with the mobile operator.
The technology used initially was analog tacs.
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With this system the transmissions in each radio cell occurred at different frequencies to allow the coexistence of adjacent cells, but there were various limitations including that of being able to transmit simultaneously, by each radio station, only a limited number of calls making it impossible in this way, making calls at peak traffic times.
Furthermore, in addition to voice communication, it was not possible to have additional services such as sending sms, faxes and emails.
There was also a high risk of cloning the mobile phone by altering the identification code and calls could only be made while in Italy.
After a few years, the first GSM mobile phones were launched on the market, followed later by the umts which, making the tacs obsolete, decreed its end in 2005.
The prices of gsm cell phones often vary downwards due to new umts cell phones equipped with ever new functions that cause cellular discounts on models considered now outdated.
The Global System for Mobile Communications simply called Gsm is the second most popular second generation mobile phone standard with over three billion people who use it worldwide.
Thanks to the widespread use of GSM, many mobile operators in various states have entered into roaming agreements, i.e. automatic communication between the operator of our country and that of the country of destination which simplifies the use of their mobile phone in foreign countries.
The technology behind GSM is totally different from that of tacs, especially for the digitalization of the signal.
The new system has allowed users to access many new services including the popular sms and mms.
The costs of umts mobile phones are influenced by the continuous promotions offered by cell phones that each operator makes even reaching zero or at a symbolic cost compared to the value of the object if the user changes the mobile phone company using the portability of his own number.
To find out which are the best cell phones, you can read cell reviews in sector magazines but this is not always enough to guarantee the purchase of the latest cell phone models released on the market as there are still not enough testimonials from other users on the correct operation.
For this reason, it is sometimes preferable to search among the cell phone deals, preferring to buy a dated but certainly reliable cell phone model as it is well tested.
Universal Mobile Telecommunications System or Umts represents the third generation mobile phone technology that allows even better performance with even faster audio and video data transmission.
Cell phone repair is often not convenient for models over two years of age as they would buy equivalent phones without having to spend a greater amount than the repair would cost us.
The online sale of videophones and cell phones with integrated digital camera is mainly focused on the models that are most popular with the public.
