There is a type of low power two-way radio base station, which serves a coverage area, divided into many smaller zones (cells). Telephone handsets continuously search for the closest base station, and hop from base station to base station if the user was on the move. This strategy of replacing one high power base station with many low power base stations distributed throughout the coverage area made it possible to handle far more subscribers, and reduced the power requirements for wireless telephones.
Reducing the amount of power needed to carry a conversation through the airwaves, made it possible for manufacturers to produce much smaller phones. While solid state circuitry advances have played an important role in reducing the size and weight of portable phones, the reduction of power requirements eliminated the need for bulky, heavy batteries to power handsets.
The first cellular telephone network put to widespread use was an analog system called AMPS. An AMPS is an analog, frequency modulation scheme (the same scheme used in FM radio). At the time cellular was introduced, FM modulation/demodulation circuitry was a commodity product, and so this was the most cost effective way to introduce cellular service. Digital cellular did not become cost effective until the 1990s when DSP based platforms came down in price enough to make it practical to create an all-digital telephone handset.
HOW IT WORKS:

A cell phone has become easily accessible today, as it can fit in most pockets. (pun intended!) a decent cell-phone will be available starting Rs. 5000/- and of course, the sky is the limit if you want an expensive model. Another thing to note is that cell phone prices are going down as the market becomes more competitive.
Small is in. At least where the cell phones go. The new tiny single-chassis phones are called "candy bar" models, a reference to their shape. Many weigh less than 200 grams, battery included. The familiar squat flip-phones -- those that open like communicators from the old "Star Trek" -- also are ultra-light.
Batteries are getting smaller too. New nickel metal hydride (NiMH) batteries are smaller and lighter than the Nickel Cadmium (NiCad) batteries, but often provide about 40 percent less power. The latest batteries are the Lithium Ion (Li-Ion) and the Lithium Polymer batteries, which are of superior quality.
The Cellular Telecommunications Industry Association (CTIA) is a standard performance testing association for cell phones. Like an ISI seal, it too has an approval seal.

Your cell phone is tailor-made to deal with tough conditions, which come from the fact that it is a mobile service. But nonetheless, the instruments can take only so much abuse, and are susceptible to breaking.

Cellular Phone Carrier:
The normal subscription system, where you get a monthly bill for all calls made.
Prepaid Cellular Phone:
You pay for the service in advance, where the amount in your account is debited with per call made. When the account has been used, you have to get a new card. A pre-paid phone service does not require the initial investment as the monthly service. However, the per call cost is more in a pre-paid. Also, benefits like free night-talk, and others are not available.
Cellular Phone Accessories:
Extra batteries, vehicle antennas, battery chargers / conditioners, battery eliminators, hands free kits, and leather cases, are all the accessories available.
Hands Free:
An important safety feature that's included with most of today's mobile phones. It permits drivers to use their cellular phone without lifting or holding the handset to their ear. You can speak into your handset by placing it near you during a conversation.
Voice Activated Dialing:
A feature available only on selected phones and hands-free car kits that permits you to dial numbers by calling them out to your cellular phone, instead of dialing them manually. This function is especially convenient for making calls from your vehicle while driving.

How to use your phone as a modem:
You can go online to send faxes and e-mail using your cellular phone as a wireless "modem" for your laptop. To do this, you'll need a phone that can function as a modem, a cable to connect your phone to your laptop, and a carrier that offers Internet or data options. For cellular phones without a built-in modem, you'll need to purchase a cellular-compatible PC card modem that works with your laptop. You'll also need a compatible cable to connect the card modem in the laptop to your cell phone. Sometimes the PC card and cable are packaged together as a kit i.e. You can click on the Service Plans tab to see which carriers in your market sell that phone.
Newer phones have built-in modem capability, so your laptop doesn't need a PC card, but you'll still have to purchase a compatible cable to connect the phone to your laptop's serial port.
Getting Web Updates on your phone:
Some carriers offer news, stock and sports updates with activation of a Web-messaging option or service plan. Other carriers provide free news updates as long as you subscribe to text-messaging services.
When you sign up for these services, carriers require you to establish an account either on their Web site or on a Web site designed to provide your updates. Once you establish an account, you will be able to select and modify your updates, including when you receive them, simply by accessing your account via the Web site.
The updates arrive as text messages (also called short messaging service), so your phone needs to support this feature. Depending on the carrier, updates are subject to character limitations ranging from 100 to 150 characters.
Alarm Clocks on phones:
With most phones, you simply select the alarm option and enter a time. Some alarms will work even when the phone is turned off. Usually, the phone's alarm will sound just like your ringer alert.
E-mail and Faxes on your phone:
You can also send and receive data/fax documents, access the internet, email accounts and corporate databases whenever you are on the move. All you need is a compatible phone and computer and the connecting accessories (unless you use infrared). Your mobile acts as a phone line. Calls are normally charged at the same rate as voice calls. You can ask for this facility from your phone service, for just a little extra charge. And then, you become truly global! In touch with the world at your fingertips!
Screening your calls:
A caller ID displays the caller's number on your phone's screen. It is standard with many digital cellular and PCS (Personal Communications Service) carriers. Some callers can't be identified, depending on how their call is routed to you.
Locking your Phone:
Locking your cell phone is a great way to ensure you're the only one using your handset. Once you activate the lock mode, you must enter a four-digit code on the keypad each time you turn on the phone. This prevents anyone else from making calls or accessing the phone's memory or menu functions.
Tracking Battery Strength:
Your phone can indicate on its screen when your battery is almost out of power. The indicator can be a battery icon, a "battery low" message or a red light.

Although no conclusive evidence has been found linking mobile phone exposure to brain cancer, several new studies suggest that the potential threat to health is greater than previously thought. Another cause for concern is the effect on health due to Radio Frequency (RF) exposure. RF can penetrate exposed tissue, is absorbed by the body and produces heat although the body's normal thermo regulating process carries this heat away.
According to new WHO (World Health Organisation) guide rules:

Let your personal phone be personal:
Be discreet about giving out your number
Only give your number to people you actually know, it's your money you'll be spending when they ring you up.

A cell phone should be used as a device for communicating. Your chats can be left for a landline. Use your phone smartly to save on your bills.
Buy smart, talk smart, and save money on your cell-phones. Cell phone technology has gone on to make the world smaller, and at your fingertips. Also people can keep in touch and trace each other with much more ease. So go ahead, and keep your date, even if you missed her at the taxi stand. Just talk!!
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