Communication Devices

iPad Apple

The iPad (pronounced eye-pad) is a line of tablet computers designed, developed and marketed by Apple Inc. primarily as a platform for audio-visual media including books, periodicals, movies, music, games, and web content. Its size and weight falls between those of contemporary smartphones and laptop computers. The iPad runs the same operating system as the iPod Touch and iPhone—and can run its own applications as well as iPhone applications. Without modification, the iPad will only run programs approved by Apple and distributed via the Apple App Store (with the exception of programs that run inside the iPad's web browser).

Like iPhone and iPod Touch, the iPad is controlled by a multitouch display—a departure from most previous tablet computers, which used a pressure-triggered stylus—as well as a virtual onscreen keyboard in lieu of a physical keyboard. The iPad uses a wireless local area network("Wi-Fi") connection to access local area networks and the Internet. Some models also have a 3G wireless network interface which can connect to HSPA or EV-DO data networks and on to the Internet. The device is managed and synced by iTunes running on a personal computer via USB cable.

Apple released the first iPad in April 2010, and sold 3 million of the devices in 80 days.During 2010, Apple sold 14.8 million iPads worldwide,representing 75 percent of tablet PC sales at the end of 2010.

WiFi

Wi-Fi is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point (or hotspot) has a range of about 20 meters (65 ft) indoors and a greater range outdoors. Multiple overlapping access points can cover large areas.

"Wi-Fi" is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11family of standards. Wi-Fi is used by over 700 million people. There are over four million hotspots (places with Wi-Fi Internet connectivity) around the world, and about 800 million new Wi-Fi devices are sold every year.Wi-Fi products that complete Wi-Fi Alliance interoperability certification testing successfully may use the "Wi-Fi CERTIFIED" designation and trademark.

Modem

A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from light emitting diodes to radio. The most familiar example is a voice band modem that turns the digital data of a personal computer into modulated electrical signals in the voice frequency range of a telephone channel. These signals can be transmitted over telephone lines and demodulated by another modem at the receiver side to recover the digital data.

Modems are generally classified by the amount of data they can send in a given unit of time, usually expressed in bits per second (bit/s, or bps). Modems can alternatively be classified by their symbol rate, measured in baud. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal. For example, the ITU V.21 standard used audio frequency-shift keying, that is to say, tones of different frequencies, with two possible frequencies corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud. By contrast, the original ITU V.22 standard, which was able to transmit and receive four distinct symbols (two bits per symbol), handled 1,200 bit/s by sending 600 symbols per second (600 baud) using phase shift keying.