February 27, 2017

Homework Help: cell phone

Posted by cell phone on Wednesday, February 9, 2011 at 9:37am.

Cell Phone

Cell phones let you make or take calls wherever you happen to be. A third of the world’s population now makes their phone calls this way, and around 3 billion cell phones are in use worldwide.

Screen: has a 176 x 220 pixel display that can show photos taken by the built-in camera. A graphics accelerator chip allows it to play movies, music videos, and games.

Ultra-Thin keypad: is a third of the thickness of a conventional phone keypad. Its built-in-blue light flows so that numbers are visible in the dark.

SIM: (subscriber identity module) contains a microchip that stores your personal details and can be switched from phone to phone.

Digital Camera: has a zoom lens that can magnify up to four times. Photos taken are stored in the phone’s memory and can be sent to other people’s phones.

This Cell Phone: is a handheld personal communication center, with email, Web browser, and state-of-the-art video and game player. It has a built-in camera and two color screens(one on the inside of the case and another seen when the case is closed) it weighs just 3 1/3 oz.(95 g).

The first cell phone network, Advanced Mobile Phone System, appeared in Chicago in 1978. It used a system of ten cells to link 2000 customers.

Cell phones will be built into our clothes or sunglasses. They will project no data directly into the eye – no screen required.

How Cell Phones Work
Cell phones operate within a network of cells-areas covered by a radio transmitter mast known as a base station. Cells vary in size but overlap slightly, so that when you move from one cell to another your call can be handed off (passed without interruption) from one cell to the next. A central exchange links the cells; it also connects one cellular network (usually operated by one company) to other cellular networks and to the landline (wired phone) network.

Bluetooth: headset with built-in microphone and earpiece speaker lets you answer calls and talk to people without touching the phone itself. Bluetooth is a method of controlling electronic devices, without wires, over short distances. Signals are sent via short-range radio waves.

Lithium-ion battery gives 7 hours of talk time. Mouthpiece, using phones voice recognition feature, lets you call a persons number by saying their name. Anodized aluminum case is a strong, light, and durable.

How one cell phone calls another
1. Signal form cell phone a sent to base station via radio waves.
2. Underground cable carries signal to cellular exchange.
3. Transmitter at cellular exchange sends signal to base station closest to cell phone B.
4. Microwave link beams signal to base station.
5. Signal beamed from base station to cell phone B via radio waves.

Base station can cover a large area in rural areas since there are fewer cell phone uses than in cities.

Cellular exchange connects to base station via microwave beams or underground cables.

Cells of cellular network each contain a base station.

Cell phones send and receive calls as streams of digital data. This has many advantages over the analog technology still used in many landlines. There is less interference and better sound quality. Digital calls can be encrypted (scrambled) to prevent eavesdropping. Cell phones also send and receive voice, fax, text, and Internet data. Cellular networks can carry more digital calls then landline networks. Some send information using packet switching, just like the internet.

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