This Allows Efficient Use Of The Limited Radio Spectrum Allocated To Mobile Services, And Lets Thousands Of Subscribers Converse At The Same Time Within A Given Geographic Area.
Once These Few Channels Were In Use By Customers, No Further Customers Could Be Served Until Another User Vacated A Channel. It Would Be Impractical To Give Every Customer.
In The Earliest Mobile Phone Systems By Contrast, All Control Was Done Manually; The Customer Would Search For An Unoccupied Channel And Speak To A Mobile Operator To Request Connection.
Mobile Phones Communicate With Cell Towers That Are Placed To Give Coverage Across A Telephone Service Area, Which Is Divided Up Into 'cells'. Each Cell Uses A Different Set Of Frequencies.
A display which echoes the user's typing, and displays text messages, contacts, and more. The display is typically either a liquid-crystal display (LCD) or organic light-emitting diode (OLED) display.
A battery, providing the power source for the phone functions. A modern handset typically uses a lithium-ion battery (LIB), whereas older handsets used nickel–metal hydride batteries.
A central processing unit (CPU), the processor of phones. The CPU is a microprocessor fabricated on a metal–oxide–semiconductor (MOS) integrated circuit (IC) chip.
The Critical Advantage That Modern Cellular Networks Have Over Predecessor Systems Is The Concept Of Frequency Reuse Allowing Many Simultaneous Telephone Conversations In A Given Service Area.
Former Systems Would Cover A Service Area With One Or Two Powerful Base Stations With A Range Of Up To Tens Of Kilometres (Miles), Using Only A Few Sets Of Radio Channels Frequencies.
These Systems Have Dozens Or Hundreds Of Possible Channels Allocated To Them. When A Subscriber Is Using A Given Channel For A Telephone Connection, That Frequency Is Unavailable For Other Customers.
In The Local Cell And In The Adjacent Cells. However, Cells Further Away Can Re-use That Channel Without Interference As The Subscriber's Handset Is Too Far Away To Be Detected.
The Automation Systems Can Control The "Hand Off" Of A Customer Handset Moving Between One Cell And Another So That A Call In Progress Continues Without Interruption, Changing Channels If Required.
An input mechanism to allow the user to interact with the phone. These are a keypad for feature phones, and touch screens for most smartphones (typically with capacitive sensing).
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