Cell phones

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The cell phone combines the technology from the telephone (Alexander Graham Bell 1876) and the radio (Nikolai Tesla in the 1880s). Every wireless component have technology that can be traced back to the radio. Today almost everyone in Scandinavia between 15 and 50 have a cell phone. Cell phones are such an important tool in the social and professional life that it is almost impossible not to have a one. The number of children below 13 who have there own mobile phone is increasing and many people say it will cause the children harm. A massive number of debates and rapports have come and gone and the question still is: Is cellular phones dangerous? To answer this we must first understand how a cell phone works and how it transmits its information.
The technology of mobile phones
The cell phones transmit their sound through radio waves.
The first more or less mobile phones were situated in cars. The phones transmitted the waves on a specific frequents to a large antenna in town. That antenna had about 25 channels in which the transmission could be sent. Since there only where 25 there were not were many people how could have car phones because if every channel was engaged then you couldn’t make a call. Someone thought that if we divide the transmissions area in to smaller cells and let them send low-power transmissions then several cell carriers can use the same frequencies at the same time. The advantages of low-power are first of all, the need less power. This is what made handheld phones which were run by batteries possible. The second advantage is because of the smaller power the waves don’t come as long. To cells which are not situated between each other (non-adjacent) can therefore use the same frequency at the same time. Each cell covers an area of about 26 square kilometers. A normal cell phone carrier has about 832 channels to transmit to. Since every call uses two frequencies per call (duplex-channel) then usually there is room for about 395 voice channels per carrier. The final 42 is used for control channels which are needed to talk to a cell phone in order to transmit on the right frequency to the cell phone. This means that each cell can have about 52 calls at the same time. With digital techniques the number of calls can increase with 300 %.
What differences a walkie-talkie from a cell phone is the type of channel they use. A walkie-talkie only has one frequency and it has a half-duplex channel. A half-duplex channel means that only one frequency is used to talk. This means that only one person can talk at one time. A cell phone has a full-duplex channel and can use over 1 664 frequencies at the same time. In a full-duplex channel two people can talk at the same time and the use to channels to talk to each other. One is for talking and the other for listening. A walkie-talkie often have low-power. It transmits with a power of 0.6 watt or 3 watt. A walkie-talkie can transmit about 1,6 kilometer (1 mile). A modern cellular phone can switch between cells when talking and can therefore transmit for almost unlimited areas as long as there are enough cell carriers. What makes this possible is following:
Every cell carrier is connected to a base station. In a normal sized town there can be over 100 base stations. A base station is an antenna and a small house with contents all the radio equipment necessary for the transmitting. The base station is connected to a Mobile Telephone Switching Office (MTSO). Each carrier has a MTSO. The MTSO handles al of the phone connections and control the base station in the region. When you are walking around talking in...