The term wireless is normally used to refer to any type of electrical or electronic operation which is accomplished without the use of a "hard wired" connection, though they may be accomplished with the use of wires if desired. Wireless communication is the transfer of information over a distance without the use of electrical conductors or "wires". The distances involved may be short (a few meters as in television remote control) or very long (thousands or even millions of kilometers for radio communications). When the context is clear the term is often simply shortened to "wireless". Wireless communications is generally considered to be a branch of telecommunications.
The term wireless technology is generally used for mobile IT equipment. It encompasses cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless technology include GPS units, garage door openers and or garage doors, wireless computer mice and keyboards, satellite television and cordless telephones.

Introduction
Further information: History of radio
The term "wireless" came into public use to refer to a radio receiver or transceiver (a dual purpose receiver and transmitter device), establishing its usage in the field of wireless telegraphy early on; now the term is used to describe modern wireless connections such as in cellular networks and wireless broadband Internet. It is also used in a general sense to refer to any type of operation that is implemented without the use of wires, such as "wireless remote control", "wireless energy transfer", etc. regardless of the specific technology (e.g., radio, infrared, ultrasonic, etc.) that is used to accomplish the operation.

History
David E. Hughes, eight years before Hertz's experiments, induced electromagnetic waves in a signalling system. Hughes transmitted Morse code by an induction apparatus. In 1878, Hughes's induction transmission method utilized a "clockwork transmitter" to transmit signals. In 1885, T. A. Edison uses a vibrator magnet for induction transmission. In 1888, Edison deploys a system of signalling on the Lehigh Valley Railroad. In 1891, Edison attains the wireless patent for this method using inductance (U.S. Patent 465,971 ).
In the history of wireless technology, the demonstration of the theory of electromagnetic waves by Heinrich Rudolf Hertz in 1888 was important. The experiments were not followed up by Hertz and the practical applications of the wireless communication and remote control technology would be implemented by Nikola Tesla.

Early wireless work
We are all affected by the electromagnetic spectrum in our daily lives. Light, colors, AM and FM radio, and many popular electronic devices all work on the electromagnetic spectrum. In the US the frequencies that are available for use for communication are treated as a public resource and are regulated by the Federal Communications Commission (FCC). This is a very important role because it determines which frequency ranges can be used for what purpose and by whom. This may sound very controlled, but just imagine the chaos if, for example, airlines didn't have specific frequencies to work under and some ham radio buff was interfering with the pilot's ability to land an airplane. Wireless communication spans the spectrum from 9 kHz to 300 GHz. It must be remembered that the airwaves are a spectrum. This means frequencies close to each other can interfere with each other if not regulated properly. Medical equipment and cell phones are not a very good mix and that is why cell phone use is banned in hospitals and doctors' offices.

The electromagnetic spectrum

Examples of wireless technology at work
One common example of an operation or operations where the implementation of wireless technology may supplement or replace hard wired implementations is in security systems for homes or office buildings. The operations that are required (e.g., detecting whether a door or window is open or closed) may be implemented with the use of hard wired sensors or they may be implemented with the use of wireless sensors which are also equipped with some type of wireless transmitter (e.g., infrared, radio frequency, etc.) to transmit the information concerning the current state of the door or window.

Security systems
Another example would be the use of a wireless remote control unit to replace the old hard wired remote control units that were sometimes used in the television industry. Some televisions were previously manufactured with hard wired remote controls which plugged in to a receptacle or jack in the television whereas more modern televisions use wireless (generally infrared) remote control units.

Cellular telephones
Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or the entire communication path. Common examples of wireless equipment in use today include:
Wireless networking is used to meet a variety of needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology:

Cellular phones and pagers: provide connectivity for portable and mobile applications, both personal and business.
Global Positioning System (GPS): allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth.
Cordless computer peripherals: the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless.
Cordless telephone sets: these are limited-range devices, not to be confused with cell phones.
Satellite television: allows viewers in almost any location to select from hundreds of channels.
To span a distance beyond the capabilities of typical cabling,
To avoid obstacles such as physical structures, EMI, or RFI,
To provide a backup communications link in case of normal network failure,
To link portable or temporary workstations,
To overcome situations where normal cabling is difficult or financially impractical, or
To remotely connect mobile users or networks. Wireless communication
In recent time there are concerns and research linking usage of wireless communications with poor concentration, memory loss, nausea, premature senility and even cancer.

Environmental concerns and health hazard
DECT (Digital Enhanced Cordless Telecommunications)
0G, 1G, 2G, 3G, 4G, Beyond 4G or 5G
Wireless microphones, Remote controls, IrDA, RFID (Radio Frequency Identification), Wireless USB, DSRC (Dedicated Short Range Communications), EnOcean, Near Field Communication
ZigBee, EnOcean; Personal area networks, Bluetooth, Ultra-wideband (UWB from WiMedia Alliance).
Wireless Local Area Networks (WLAN), (IEEE 802.11 branded as WiFi and HIPERLAN), Wireless Metropolitan Area Networks (WMAN) and Broadband Fixed Access (BWA) (LMDS, WiMAX, and HIPERMAN)

Broadcasting

Amateur radio

Communication radio

Cordless telephony

DECT (Digital Enhanced Cordless Telecommunications)

Cellular systems

0G, 1G, 2G, 3G, 4G, Beyond 4G or 5G

Short-range point-to-point communication 

Wireless microphones, Remote controls, IrDA, RFID (Radio Frequency Identification), Wireless USB, DSRC (Dedicated Short Range Communications), EnOcean, Near Field Communication

Wireless sensor networks 

ZigBee, EnOcean; Personal area networks, Bluetooth, Ultra-wideband (UWB from WiMedia Alliance).

Wireless computer networks

Wireless Local Area Networks (WLAN), (IEEE 802.11 branded as WiFi and HIPERLAN), Wireless Metropolitan Area Networks (WMAN) and Broadband Fixed Access (BWA) (LMDS, WiMAX, and HIPERMAN)

See also