Mobile Phones - A Wonder or A Blunder by Chitsank http://www.angelfire.com/zine2/chitsank/main.htm In a mob, if you don't hear the beep of one or two mobile phones, you can consider yourself deaf. Yes, these Cell phones have invaded our lives and we spend most of our time with this small wonder glued to our ears. In a world that's full of change and dynamic, where people are constantly on the move across miles, there is a dire need for communication and the cell phones do the trick for you. These Wireless telephones otherwise called PCS phones are provided with built-in antennas and are easily portable 'coz of their size. These small wonders play a vital role when the land lines are down. This tiny hand- held gadget has intruded our life and has changed the way we communicate. Messaging has increased and it threatens to put a full stop to verbal communication. A new language of texting with acronyms (btw, asap etc.) and shortcut (oic, cya etc.), s has evolved due to the need for speedy messaging. The cell phones have become a fashion accessory. Especially for teenagers. They provide the biggest market. They spend most of their pocket money on pre paid cards. The popular "Expression- series by Nokia focuses on teenagers and includes games and easy text messaging. Cell phones make a person easily accessible. You can contact a person whenever you need them wherever they are. For people living faraway from their homes, a cell phone is an easy and cheap mode of communication. This offers a solution to the high bills paid for long distance calls (ISTD). Hence using cell phones has become a necessary habit. This awesome device connects people across the globe with its roaming facility and their cost continues to decrease with their increased use. The cost will continue to drop as the market size grows and more capable and increasingly cheaper to operate technologies happen. The future cell phones will be integrated with add on technologies like a personal digital assistant, Global Positioning System etc. which will endow a more productive business ambiance and will also provide for the expansion of trade networks across our planet and who knows maybe across alien planets too. There are many useful features in a mobile phone. The 'hands free' feature permits drivers to use their cellular phone without lifting or holding the handset. Message alert: feature wherein a blinking light indicates that a phone call came in. Voice mail a computerized answering service that automatically answers your call, plays a greeting in your own voice and records a message is another key feature in most cell phones. Since each cell is designed to use radio frequencies only within its boundaries, the same frequencies can be reused in other cells not far away with little or no interference. The reuse of frequencies enables a cellular system to handle a huge number of calls with a limited number of channels. Cell phones play an essential role in the mobile communication of the modern world. But, what about those dark ages before cell phones came into existence? How did people handle mobile communications? Well, they used radiotelephones. The radiotelephone system had one central antenna tower per city, and perhaps 25 channels available on that tower. This central antenna meant that the phone in your car needed a powerful transmitter -- big enough to transmit 40 or 50 miles (about 70 km). It also meant that not many people could use radiotelephones -- there just were not enough channels. How the Cellular System works: Today's cellular system divides a city into small cells. This enables extensive frequency reuse across a city, so that millions of people can use cell phones simultaneously. Each cell comprises of a base station with a tower and a building to house the radio equipment. Each cell uses one- seventh of the available channels so it has a unique set of frequencies and there are no collisions. A cell-phone carrier typically has 832 radio frequencies to use in a city. Each cell phone uses two frequencies per call -- a duplex channel -- so there are 395 voice channels per carrier. (The other 42 frequencies are used for control channels) Therefore, each cell has about 56 voice channels available. Simply put, there are about 56 people talking from their cell phones in a cell in an analog system. In a digital system there are more number of channels. A digital system can carry three times as many calls as an analog system, so each cell has about 168 channels. The cellular approach requires a large number of base stations in a city of any size. A city can have hundreds of towers. Each carrier in each city runs a central office called the Mobile Telephone Switching Office (MTSO). The office handles the phone connections to the normal land- based phone system, and controls the entire base stations in that region. How Do Calls get transmitted: When you switch on the phone, it listens for an SID (System Identification Code - a unique 5-digit number that is assigned to each carrier by the respective authority) on the control channel. The control channel is a special frequency where the phone and base station talk to one another about the details of call set-up and channel changing. If the phone fails to recognize a control channel, it knows it is out of range and displays a "no service" message. When it receives the SID, the phone compares it with the SID programmed in your phone. If the SIDs match, the phone knows that the cell it is communicating is part of its home system. Along with the SID, the phone transmits a registration request, and the MTSO keeps track of your phone's location in a database so that the MTSO knows which cell you are in when it wants to ring your phone. The MTSO gets the call, and it tries to find you. It looks in its database to see which cell you are in. The MTSO picks a frequency pair that your phone will use in that cell to take the call. The MTSO communicates with your phone over the control channel to tell it which frequencies to use, and once your phone and the tower switch are on those frequencies, the call is connected and Lo! You are talking to your friend! As you move away from your cell, your cell's base station notes that the strength of your signal is diminishing. Meanwhile, the base station you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) detects the strength of your phone signal increasing. The two base stations coordinate with each other through the MTSO, and at some point, your phone gets a signal on a control channel asking it to change frequencies. Thus the signal is passed from cell to cell as you travel. Roaming If the SID on the control channel does not match the SID programmed into your phone, then the phone knows it is roaming. The MTSO of the cell that you are roaming in contacts the MTSO of your home system, which checks its database, to confirm whether the SID of the phone you are using is valid. Your home system verifies your phone to the local MTSO, which tracks your phone as you move through its cells. In all these processes, your voice travels in the form of radio waves and this fact has led to controversies in using the cell phones. Well, Are they dangerous? Here are a few assumptions that are believed to ensue from the use of cell phones: Radio waves emitted from mobiles heat-up body tissue. Magnetic fields created by mobile phones influence the behavior of body cells. Long mobile phone calls cause fatigue, headaches, and loss of concentration. Mobile phone users are susceptible to cancer in areas of the brain adjacent to their ears. Radio waves from mobile phones alter the gene expression. All the above assumptions are baseless until proved. While scientists are still slogging on this line of infinite research, the never-ending craze for cell phones has reached an insurmountable peak. Since these elegant cell phones have amplified the expediency of today's communication, the allegations on the health front are overlooked. The cell phone industry is the fastest growing in today's world. And this handheld small gadget has not only revolutionized the modern communication but the novelty of this small wonder has also captivated the world with its ever-fascinating charm. This article courtesy of the MOBILE PHONE Newsletter: http://www.mobilephonesite.co.uk