Walkie-talkie
Overview
 
A walkie-talkie is a hand-held, portable, two-way radio
Two-way radio
A two-way radio is a radio that can both transmit and receive , unlike a broadcast receiver which only receives content. The term refers to a personal radio transceiver that allows the operator to have a two-way conversation with other similar radios operating on the same radio frequency...

  transceiver
Transceiver
A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...

. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross
Alfred J. Gross
Alfred J. Gross , a.k.a. Irving J. Gross was a pioneer in mobile wireless communication. He created and patented many communications devices, specifically in relation to an early version of the walkie-talkie, Citizens' Band radio, the telephone pager and the cordless telephone...

, and engineering teams at Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

. Similar designs were created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work. Major characteristics include a half-duplex
Duplex (telecommunications)
A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. The term multiplexing is used when describing communication between more than two parties or devices....

 channel (only one radio transmits at a time, though any number can listen) and a "push-to-talk" (PTT) switch that starts transmission
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...

.
Encyclopedia
A walkie-talkie is a hand-held, portable, two-way radio
Two-way radio
A two-way radio is a radio that can both transmit and receive , unlike a broadcast receiver which only receives content. The term refers to a personal radio transceiver that allows the operator to have a two-way conversation with other similar radios operating on the same radio frequency...

  transceiver
Transceiver
A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...

. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross
Alfred J. Gross
Alfred J. Gross , a.k.a. Irving J. Gross was a pioneer in mobile wireless communication. He created and patented many communications devices, specifically in relation to an early version of the walkie-talkie, Citizens' Band radio, the telephone pager and the cordless telephone...

, and engineering teams at Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

. Similar designs were created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work. Major characteristics include a half-duplex
Duplex (telecommunications)
A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. The term multiplexing is used when describing communication between more than two parties or devices....

 channel (only one radio transmits at a time, though any number can listen) and a "push-to-talk" (PTT) switch that starts transmission
Transmission (telecommunications)
Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...

. Typical walkie-talkies resemble a telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...

 handset
Handset
On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient...

, possibly slightly larger but still a single unit, with an antenna sticking out of the top. Where a phone's earpiece is only loud enough to be heard by the user, a walkie-talkie's built-in speaker can be heard by the user and those in the user's immediate vicinity. Hand-held transceivers may be used to communicate between each other, or to vehicle-mounted or base stations.

History

The first radio receiver/transmitter to be widely nicknamed "Walkie-Talkie" was the backpacked Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

 SCR-300
SCR-300
The SCR-300 was a portable radio transceiver used by US Signal Corps in World War II. This backpack-mounted unit was the first two way radio to be nicknamed a "walkie talkie".- History :...

, created by an engineering team in 1940 at the Galvin Manufacturing Company (fore-runner of Motorola). The team consisted of Dan Noble
Daniel E. Noble
Daniel Earl Noble was an American engineer, and Executive Vice Chairman of the Board emeritus of Motorola,who is known for the design and installation of the nation's first statewide two-way radio...

, who conceived of the design using frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...

, Raymond Yoder, Henryk Magnuski
Henryk Magnuski
Henryk Władysław Magnuski was a Polish telecommunications engineer who worked for Motorola in Chicago. He was the inventor of one of the first Walkie-Talkies and one of the authors of his company success in the fields of radio communication.-Early years:Magnuski was born on January 30, 1909 in...

 who was the principal RF engineer
Radio frequency engineering
Radio frequency engineering is the analysis and design of circuits at frequencies where transmission lines are comparable to the wavelength. It includes the study of amplifiers, oscillators, mixers, demodulators and antennas. This is relevant to RFID, broadcasting, radar, wireless computer...

, Marion Bond, Lloyd Morris, and Bill Vogel.

Motorola also produced the hand-held AM SCR-536
SCR-536
The SCR-536 was a hand-held radio transceiver used by US Signal Corps in World War II. It is popularly referred to as a walkie talkie although it was originally designated a "handie talkie".- History :...

 radio during World War II, and it was called the "Handie-Talkie" (HT). The terms are often confused today, but the original walkie talkie referred to the back mounted model, while the handie talkie was the device which could be held entirely in the hand (but had vastly reduced performance). Both devices ran on vacuum tubes and used high voltage dry cell
Dry Cell
-Dry Cell's formation:Part of the band formed in 1998 when guitarist Danny Hartwell and drummer Brandon Brown met at the Ratt Show on the Sunset Strip. They later met up with then-vocalist Judd Gruenbaum. The original name of the band was "Beyond Control"....

 batteries. (Handie-Talkie became a trademark of Motorola, Inc. on May 22, 1951. The application was filed with the U.S. Patent and Trademark Office, and the trademark registration number is 71560123.)

Radio engineer Alfred J. Gross
Alfred J. Gross
Alfred J. Gross , a.k.a. Irving J. Gross was a pioneer in mobile wireless communication. He created and patented many communications devices, specifically in relation to an early version of the walkie-talkie, Citizens' Band radio, the telephone pager and the cordless telephone...

 also worked on the early technology behind the walkie-talkie between 1934 and 1941, and is sometimes credited with inventing it. Gross had developed and tested a small portable high-frequency radio with two-way communications features which he dubbed a "walkie-talkie". The device caught the attention of the U.S. Office of Strategic Services (now the Central Intelligence Agency
Central Intelligence Agency
The Central Intelligence Agency is a civilian intelligence agency of the United States government. It is an executive agency and reports directly to the Director of National Intelligence, responsible for providing national security intelligence assessment to senior United States policymakers...

), which recruited him to develop the Joan-Eleanor system
Joan-Eleanor system
The Joan-Eleanor system was a very high frequency radio system developed during World War II for use by agents working behind enemy lines to relay information and replaced the earlier S-Phone system used by agents....

, a two-way, air-to-ground radio system for covert use by troops behind enemy lines during World War II.

Also credited with the invention of the walkie talkie is Canadian inventor Donald Hings
Donald Hings
Donald Lewes Hings, was a Canadian inventor. In 1937 he created a portable radio signaling system for his employer CM&S, which he called a "packset", but which later became known as the "Walkie-Talkie"....

 who created a portable radio signaling system for his employer CM&S in 1937 which he called a "packset", but which later became known as the "walkie talkie". Hings was formally decorated for its significance to the war effort. Hing's model C-58 "Handy-Talkie" was in military service by 1942, the result of a secret R&D effort that began in 1940.

Following World War II, Raytheon
Raytheon
Raytheon Company is a major American defense contractor and industrial corporation with core manufacturing concentrations in weapons and military and commercial electronics. It was previously involved in corporate and special-mission aircraft until early 2007...

 developed the SCR-536's military replacement, the AN/PRC-6
AN/PRC-6
The AN/PRC-6 is a walkie-talkie used by the U.S. military in the late Korean War era through the Vietnam War. Raytheon developed the RT-196/PRC-6 following World War II as a replacement for the SCR-536 "handy-talkie". The AN/PRC-6 operates using wide-band FM on a single crystal controlled frequency...

. The AN/PRC-6 circuit uses 13 vacuum tubes (receiver and transmitter); a second set of 13 tubes is supplied with the unit as running spares. The unit is factory set with one crystal and may be changed to a different frequency in the field by replacing the crystal and re-tuning the unit. It uses a 24 inch whip antenna. There is an optional handset H-33C/PT that can be connected to the AN/PRC-6 by a 5 foot cable. A web sling is provided.

In the mid-1970s the Marine Corps
Marine corps
A marine is a member of a force that specializes in expeditionary operations such as amphibious assault and occupation. The marines traditionally have strong links with the country's navy...

 initiated an effort to develop a squad
Squad
In military terminology, a squad is a small military unit led by a non-commissioned officer that is subordinate to an infantry platoon. In countries following the British Army tradition this organization is referred to as a section...

 radio to replace the unsatisfactory helmet-mounted AN/PRR-9 receiver and receiver/transmitter hand-held AN/PRT-4 (both developed by the Army). The AN/PRC-68 was first produced in 1976 by Magnavox
Magnavox
Magnavox is a US electronics company founded by Edwin Pridham and Peter L. Jensen, who invented the moving-coil loudspeaker in 1915 at their lab in Napa, California. They formed Magnavox in 1917 in order to market their inventions....

, was issued to the Marines in the 1980s, and was adopted by the US Army as well.

The abbreviation HT, derived from Motorola's "Handie Talkie" trademark, is commonly used to refer to portable handheld ham
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

 radios, with "walkie-talkie" often used as a layman's term or specifically to refer to a toy. Public safety or commercial users generally refer to their handhelds simply as "radios". Surplus Motorola Handie Talkies found their way into the hands of ham radio operators immediately following World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Motorola's public safety radios of the 1950s and 1960s, were loaned or donated to ham groups as part of the Civil Defense
Civil defense
Civil defense, civil defence or civil protection is an effort to protect the citizens of a state from military attack. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation, and recovery...

 program. To avoid trademark infringement, other manufacturers use designations such as "Handheld Transceiver" or "Handie Transceiver" for their products.

Developments

Some cellular telephone networks offer a push-to-talk handset that allows walkie-talkie-like operation over the cellular network, without dialling a call each time.

Walkie-talkies for public safety, commercial and industrial uses may be part of trunked radio system
Trunked radio system
A trunked radio system is a complex type of computer-controlled radio system. Trunked systems use a few channels , and can have virtually unlimited talkgroups. The control channel computer sends packets of data to enable one talkgroup to talk together, regardless of frequency...

s, which dynamically allocate radio channels for more efficient use of limited radio spectrum. Such systems always work with a base station
Base station
The term base station can be used in the context of land surveying and wireless communications.- Land surveying :In the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS...

 that acts as a repeater and controller, although individual handsets and mobiles may have a mode that bypasses the base station.

Contemporary use

Walkie-talkies are widely used in any setting where portable radio communications are necessary, including business, public safety, military, outdoor recreation, and the like, and devices are available at numerous price points from inexpensive analog units sold as toys up to ruggedized (i.e. waterproof or intrinsically safe) analog and digital units for use on boats or in heavy industry. Most countries, at the very least, will allow the sale of walkie-talkies for business, marine communications
Marine VHF radio
Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz...

, and some personal uses such as CB radio, as well as amateur radio designs. Walkie-talkies, thanks to increasing use of miniaturized electronics, can be made very small, with some personal two-way UHF radio models being smaller than a deck of cards (though VHF and HF units can be substantially larger due to the need for larger antennas and battery packs). In addition, as costs come down, it is possible to add advanced squelch
Squelch
In telecommunications, squelch is a circuit function that acts to suppress the audio output of a receiver in the absence of a sufficiently strong desired input signal.-Carrier squelch:...

 capabilities such as CTCSS
CTCSS
In telecommunications, Continuous Tone-Coded Squelch System or CTCSS is a circuit that is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel. It is sometimes called tone squelch...

 (analog squelch) and DCS (digital squelch) (often marketed as "privacy codes") to inexpensive radios, as well as voice scrambling and trunking capabilities. Some units (especially amateur HTs) also include DTMF keypads for remote operation of various devices such as repeater
Repeater
A repeater is an electronic device that receives asignal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.-Description:...

s. Some models include VOX
Voice operated switch
In telecommunications, a voice operated switch, also known as VOX or Voice Operated eXchange, is a switch that operates when sound over a certain threshold is detected. It is usually used to turn on a transmitter or recorder when someone speaks and turn it off when they stop speaking...

 capability for hands-free operation, as well as the ability to attach external microphones and speakers.

Consumer and commercial equipment differ in a number of ways; commercial gear is generally ruggedized, with metal cases, and often has only a few specific frequencies programmed into it (often, though not always, with a computer or other outside programming device; older units can simply swap crystals), since a given business or public safety agent must often abide by a specific frequency allocation. Consumer gear, on the other hand, is generally made to be small, lightweight, and capable of accessing any channel within the specified band, not just a subset of assigned channels.

Military

Military organizations use handheld radios for a variety of purposes. Modern units such as the AN/PRC-148
AN/PRC-148
The AN/PRC-148 Multiband Inter/Intra Team Radio is the most widely fielded handheld multiband, tactical software-defined radio, in use with NATO forces around the world. The radio is built by Thales Communications, a subsidiary of the Thales Group...

 Multiband Inter/Intra Team Radio (MBITR) can communicate on a variety of bands and modulation schemes and include encryption
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...

 capabilities.

Amateur radio

Walkie-talkies (also known as HTs or "handheld transceivers" ) are widely used among amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

 operators. While converted commercial gear by companies such as Motorola are not uncommon, many companies such as Yaesu
Yaesu (brand)
Yaesu is an international brand of commercial and amateur radio equipment.It was founded as in 1959 by a Japanese radio amateur Sako Hasegawa with callsign JA1MP in the Tokyo neighborhood of Yaesu...

, Icom, and Kenwood
Kenwood Electronics
is a Japanese manufacturer of amateur radio as well as Hi-Fidelity and portable audio equipment.-History:The company first started in 1946 as the Kasuga Radio Co. Ltd. In Komagane City, Nagano Prefecture, Japan. In 1960 the firm was renamed "Trio Corporation"...

 design models specifically for amateur use. While superficially similar to commercial and personal units (including such things as CTCSS and DCS squelch functions, used primarily to activate amateur radio repeater
Repeater
A repeater is an electronic device that receives asignal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.-Description:...

s), amateur gear usually has a number of features that are not common to other gear, including:
  • Wide-band receivers, often including radio scanner functionality, for listening to non-amateur radio bands.
  • Multiple bands; while some operate only on specific bands such as 2 meters
    2 meters
    The 2-meter amateur radio band is a portion of the VHF radio spectrum, comprising frequencies stretching from 144.000 MHz to 148.000 MHz in International Telecommunication Union region Regions 2 and 3 and from 144.000 MHz to 146.000 MHz in ITU Region 1...

     or 70 cm, others support several UHF and VHF amateur allocations available to the user.
  • Since amateur allocations usually are not channelized, the user can dial in any frequency desired in the authorized band.
  • Multiple modulation schemes: a few amateur HTs may allow modulation modes other than FM, including AM
    Amplitude modulation
    Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...

    , SSB, and CW
    Continuous wave
    A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off...

    , and digital modes such as radioteletype
    Radioteletype
    Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...

     or PSK31
    PSK31
    PSK31 or "Phase Shift Keying, 31 Baud" is a digital radio modulation mode, used primarily in the amateur radio field to conduct real-time keyboard-to-keyboard informal text chat between amateur radio operators.- History :...

    . Some may have TNCs
    Terminal node controller
    A terminal node controller is a device used by amateur radio operators to participate in AX.25 packet radio networks. It is similar in function to the Packet Assembler/Disassemblers used on X.25 networks, with the addition of a modem to convert baseband digital signals to audio tones.The TNC was...

     built in to support packet radio
    Packet radio
    Packet radio is a form of packet switching technology used to transmit digital data via radio or wireless communications links. It uses the same concepts of data transmission via Datagram that are fundamental to communications via the Internet, as opposed to the older techniques used by dedicated...

     data transmission without additional hardware.


A newer addition to the Amateur Radio service is Digital Smart Technology for Amateur Radio or D-STAR
D-STAR
D-STAR is a digital voice and data protocol specification developed as the result of research by the Japan Amateur Radio League to investigate digital technologies for amateur radio...

. Handheld radios with this technology have several advanced features, including narrower bandwidth, simultaneous voice and messaging, GPS position reporting, and callsign routed radio calls over a wide ranging international network.

As mentioned, commercial walkie-talkies can sometimes be reprogrammed to operate on amateur frequencies. Amateur radio operators may do this for cost reasons or due to a perception that commercial gear is more solidly constructed or better designed than purpose-built amateur gear.

Personal use

The personal walkie-talkie has become popular also because of the U.S. Family Radio Service
Family Radio Service
The Family Radio Service is an improved walkie talkie radio system authorized in the United States since 1996. This personal radio service uses channelized frequencies in the ultra high frequency band. It does not suffer the interference effects found on citizens' band at 27 MHz, or the...

 (FRS) and similar unlicensed services (such as Europe's PMR446
PMR446
PMR446 is a part of the UHF radio frequency range that is open without licensing for personal usage in most countries of the European Union. It has roughly the same use as FRS or GMRS in the United States and Canada. Depending on surrounding terrain range can vary from a few hundred metres to a...

 and Australia's UHF CB
UHF CB
UHF CB is a class-licensed citizen's band radio service authorised by the governments of Australia and New Zealand in the UHF 477 MHz band. UHF CB provides 77 channels, including 32 channels allocated to repeater stations...

) in other countries. While FRS walkie-talkies are also sometimes used as toys because mass-production makes them low cost, they have proper superheterodyne receivers and are a useful communication tool for both business and personal use. The boom in unlicensed transceivers has, however, been a source of frustration to users of licensed services that are sometimes interfered with. For example, FRS and GMRS overlap in the United States, resulting in substantial pirate
Pirate radio
Pirate radio is illegal or unregulated radio transmission. The term is most commonly used to describe illegal broadcasting for entertainment or political purposes, but is also sometimes used for illegal two-way radio operation...

 use of the GMRS frequencies. Use of the GMRS frequencies (USA) requires a license; however most users either disregard this requirement or are unaware. Canada reallocated frequencies for unlicensed use due to heavy interference from US GMRS users. The European PMR446 channels fall in the middle of a United States UHF amateur allocation, and the US FRS channels interfere with public safety communications in the United Kingdom. Designs for personal walkie-talkies are in any case tightly regulated, generally requiring non-removable antennas (with a few exceptions such as CB radio and the United States MURS allocation
Multi-Use Radio Service
In the United States, the Multi-Use Radio Service is an unlicensed two-way radio service similar to Citizens Band . Established by the U.S. Federal Communications Commission in the fall of 2000, MURS created a radio service allowing for unlicensed operation, with a power limit of 2 watts...

) and forbidding modified radios.

Most personal walkie-talkies sold are designed to operate in UHF allocations, and are designed to be very compact, with buttons for changing channels and other settings on the face of the radio and a short, fixed antenna. Most such units are made of heavy, often brightly colored plastic, though some more expensive units have ruggedized metal or plastic cases. Commercial-grade radios are often designed to be used on allocations such as GMRS or MURS (the latter of which has had very little readily available purpose-built equipment). In addition, CB walkie-talkies are available, but less popular due to the propagation characteristics of the 27 MHz band and the general bulkiness of the gear involved.

Personal walkie-talkies are generally designed to give easy access to all available channels (and, if supplied, squelch codes
Selective calling
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel...

) within the device's specified allocation.

Personal two-way radios are also sometimes combined with other electronic devices; Garmin
Garmin
Garmin Ltd. , incorporated in Schaffhausen, Switzerland, is the parent company of a group of companies founded in 1989 by Gary Burrell and Min Kao , that develops consumer, aviation, and marine technologies for the Global Positioning System...

's Rino series combine a GPS receiver in the same package as an FRS/GMRS walkie-talkie (allowing Rino users to transmit digital location data to each other) Some personal radios also include receivers for AM and FM broadcast radio and, where applicable, NOAA Weather Radio and similar systems broadcasting on the same frequencies. Some designs also allow the sending of text messages and pictures between similarly equipped units.

While jobsite and government radios are often rated in power output, consumer radios are frequently and controversially rated in mile or kilometer ratings. Because of the line of sight
Line-of-sight propagation
Line-of-sight propagation refers to electro-magnetic radiation or acoustic wave propagation. Electromagnetic transmission includes light emissions traveling in a straight line...

 propagation of UHF signals, experienced users consider such ratings to be wildly exaggerated, and some manufacturers have begun printing range ratings on the package based on terrain as opposed to simple power output.

While the bulk of personal walkie-talkie traffic is in the 27 MHz area and in the 400-500 MHz area of the UHF spectrum, there are some units that use the 49 MHz band (shared with cordless phones, baby monitors, and similar devices) as well as the 900 MHz band; in the US at least, units in these bands do not require licenses as long as they adhere to FCC power output rules. A company called TriSquare is, as of July 2007, marketing a series of walkie-talkies in the United States based on frequency-hopping spread spectrum
Frequency-hopping spread spectrum
Frequency-hopping spread spectrum is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver...

 technology operating in this frequency range under the name eXRS
EXtreme Radio Service
eXtreme Radio Service is a proprietary personal communication technology marketed by in the United States. The radios, which are similar to other walkie-talkies, use the 900 MHz band, and employ frequency-hopping spread spectrum technology to attempt to address some of the perceived shortcomings...

 (eXtreme Radio Service—despite the name, a proprietary design, not an official allocation of the US FCC). The spread-spectrum scheme used in eXRS radios allows up to 10 billion virtual "channels" and ensures private communications between two or more units.

Recreation

Low-power versions, exempt from licence requirements, are also popular children's toy
Toy
A toy is any object that can be used for play. Toys are associated commonly with children and pets. Playing with toys is often thought to be an enjoyable means of training the young for life in human society. Different materials are used to make toys enjoyable and cuddly to both young and old...

s such as the Fischer Price Walkie-Talkie for children illustrated in the top image on the right. Prior to the change of CB
Citizens' band radio
Citizens' Band radio is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-MHz band. Citizens' Band is distinct from the FRS, GMRS, MURS and amateur radio...

 radio from license
License
The verb license or grant licence means to give permission. The noun license or licence refers to that permission as well as to the document recording that permission.A license may be granted by a party to another party as an element of an agreement...

d to "permitted by part" (FCC rules Part 95) status, the typical toy walkie-talkie available in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 was limited to 100 milliwatts of power on transmit and using one or two crystal-controlled channels in the 27 MHz citizens' band
Citizens' band radio
Citizens' Band radio is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-MHz band. Citizens' Band is distinct from the FRS, GMRS, MURS and amateur radio...

 using amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...

 (AM) only. Later toy walkie-talkies operated in the 49 MHz band, some with frequency modulation
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...

 (FM), shared with cordless phones and baby monitors. The lowest cost devices are very simple electronically (single-frequency, crystal-controlled
Crystal oscillator
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency...

, generally based on a simple discrete transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...

 circuit where "grownup" walkie-talkies use chips
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

), may employ superregenerative
Regenerative circuit
The regenerative circuit or "autodyne" allows an electronic signal to be amplified many times by the same vacuum tube or other active component such as a field effect transistor. It consists of an amplifying vacuum tube or transistor with its output connected to its input through a feedback...

 receivers, and may lack even a volume control, but they may nevertheless be elaborately decorated, often superficially resembling more "grown-up" radios such as FRS or public safety gear. Unlike more costly units, low-cost toy walkie-talkies may not have separate microphones and speakers; the receiver's speaker sometimes doubles as a microphone while in transmit mode.

An unusual feature, common on children's walkie-talkies but seldom available otherwise even on amateur models, is a "code key", that is, a button allowing the operator to transmit Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...

 or similar tones to another walkie-talkie operating on the same frequency. Generally the operator depresses the PTT button and taps out a message using a Morse Code crib sheet attached as a sticker to the radio; however, as Morse Code has fallen out of wide use outside amateur radio circles, some such units either have a grossly simplified code label or no longer provide a sticker at all.

In addition, personal UHF radios will sometimes be bought and used as toys, though they are not generally explicitly marketed as such (but see Hasbro
Hasbro
Hasbro is a multinational toy and boardgame company from the United States of America. It is one of the largest toy makers in the world. The corporate headquarters is located in Pawtucket, Rhode Island, United States...

's ChatNow
ChatNow
ChatNow is a mobile phone-like walkie-talkie developed by Hasbro's Tiger Electronics division for the preteen market. It includes simple digital photography and text message functionality and transmits using the Family Radio Service UHF radio band...

 line, which transmits both voice and digital data on the FRS band).

Specialized uses

In addition to land mobile use, walkie-talkie designs are also used for marine VHF
Marine VHF radio
Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz...

 and aviation
Airband
Airband or Aircraft band is the name for a group of frequencies in the VHF radio spectrum allocated to radio communication in civil aviation, sometimes also referred to as VHF, or phonetically as "Victor"...

 communications, especially on smaller boats and aircraft where mounting a fixed radio might be impractical or expensive. Often such units will have switches to provide quick access to emergency and information channels.

Intrinsically safe walkie-talkies are often required in heavy industrial settings where the radio may be used around flammable vapors. This designation means that the knobs and switches in the radio are engineered to avoid producing sparks as they are operated.

Accessories

There are various accessories available for walkie talkies such as rechargeable batteries, drop in rechargers, multi-unit rechargers for charging as many as six units at a time, and an audio accessory jack that can be used for headsets or speaker microphones.

When headsets are used with voice activation (VOX) capability the user can talk with hands free operation. Several types of audio accessories are available such as speaker microphones that clip near the ear, security type earpieces with a pendant push-to-talk switch and a built-in microphone, a headset that has a push-to-talk switch earbud that looks more like what you would find on a music player, or a single-ear lightweight behind-the-head headset with boom microphone and pendant push-to-talk switch similar to that worn by a telephone call center agent.

See also

  • AN/PRC-6
    AN/PRC-6
    The AN/PRC-6 is a walkie-talkie used by the U.S. military in the late Korean War era through the Vietnam War. Raytheon developed the RT-196/PRC-6 following World War II as a replacement for the SCR-536 "handy-talkie". The AN/PRC-6 operates using wide-band FM on a single crystal controlled frequency...

  • MOTO Talk
    MOTO Talk
    MOTO Talk is a feature on some Motorola iDEN cellular phone handsets which allows users to make short-range 'push-to-talk' calls to other such handsets without being on the iDEN network. This feature goes by different names on iDEN service providers. In the US, Nextel calls it 'DirectTalk' and...

  • Push to talk
    Push to talk
    Push-to-talk , also known as Press-to-Transmit, is a method of conversing on half-duplex communication lines, including two-way radio, using a momentary button to switch from voice reception mode to transmit mode....

  • Signal Corps Radio
    Signal Corps Radio
    Signal Corps Radios were U.S. Army military communications components that comprised "sets". Under the Army Nomenclature System, SCR initially designated "Set, Complete Radio," and later "Signal Corps Radio," though interpretations have varied over time....

  • Survival radio
    Survival radio
    Survival radios are carried by ships and aircraft to facilitate rescue in an emergency. They are generally designed to transmit on international distress frequencies...

  • Two-way radio
    Two-way radio
    A two-way radio is a radio that can both transmit and receive , unlike a broadcast receiver which only receives content. The term refers to a personal radio transceiver that allows the operator to have a two-way conversation with other similar radios operating on the same radio frequency...

  • Vehicular communication systems
    Vehicular communication systems
    Vehicular Communication Systems are an emerging type of networks in which vehicles and roadside units are the communicating nodes; providing each other with information, such as safety warnings and traffic information...


Further reading

  • Dunlap, Orrin E., Jr. Marconi: The man and his wireless. (Arno Press., New York: 1971)
  • Harlow, Alvin F., Old Waves and New Wires: The History of the Telegraph, Telephone, and Wireless. (Appleton-Century Co., New York: 1936)
  • Herrick, Clyde N., Radio: Theory and Servicing. (Reston Publishing Company, Inc., Virginia 1975)
  • Martin, James. Future Developments in Telecommunications 2nd Ed., (Prentice Hall Inc., New Jersey: 1977)
  • Martin, James. The Wired Society. (Prentice Hall Inc., New Jersey: 1978)
  • Silver, H. Ward. Two-Way Radios and Scanners for Dummies. (Wiley Publishing, Hoboken, NH, 2005, ISBN 978-0-7645-9582-0)

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK