For a broader coverage related to this topic, see Two-way radio. Recreational, toy and amateur radio walkie-talkies
A walkie-talkie (more formally known as a handheld transceiver, or HT) is a hand-held, portable, two-way radiotransceiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola.First used for infantry, similar designs were created for fieldartillery and tank units, and after the war, walkie-talkies spread topublic safety and eventually commercial and jobsite work.
Typical walkie-talkies resemble a telephonehandset, with a speaker built into one end and a microphone in the other (in some devices the speaker also is used as the microphone) and an antenna mounted on the top of the unit. They are held up to the face to talk. A walkie-talkie is a half-duplexcommunication device; multiple walkie-talkies use a single radiochannel, and only one radio on the channel can transmit at a time,although any number can listen. The transceiver is normally in receivemode; when the user wants to talk he presses a "push-to-talk" (PTT) button that turns off the receiver and turns on the transmitter.
A SCR-300 backpack transceiver, nicknamed "walkie talkie"
The walkie-talkie was developed by the US military during World War2. The first radio transceiver to be widely nicknamed "Walkie-Talkie"was the backpacked MotorolaSCR-300, created by an engineering team in 1940 at the Galvin Manufacturing Company (fore-runner of Motorola). The team consisted of Dan Noble, who conceived of the design using frequency modulation; Henryk Magnuski, who was the principal RF engineer; Marion Bond; Lloyd Morris; and Bill Vogel.
A SCR-536 "handie talkie", the first walkie-talkie.
The first hand-held walkie-talkie was the AM SCR-536 transceiver also made by Motorola, named the Handie-Talkie (HT).The terms are often confused today, but the original walkie-talkiereferred to the back mounted model, while the handie-talkie was thedevice which could be held entirely in the hand. Both devices used vacuum tubes and were powered by high voltage dry cellbatteries. (Handie-Talkie became a trademark of Motorola, Inc. on May22, 1951. The application was filed with the U.S. Patent and TrademarkOffice, and the trademark registration number is 71560123.)
Alfred J. Gross, a radio engineer and one of the developers of the Joan-Eleanor system,also worked on the early technology behind the walkie-talkie between1934 and 1941, and is sometimes credited with inventing it.
Noemfoor, Dutch New Guinea, July 1944. A US soldier (foreground) uses a Handie-Talkie during the Battle of Noemfoor.
Canadian inventor Donald Hingsis also credited with the invention of the walkie-talkie: he created aportable radio signaling system for his employer CM&S in 1937. Hecalled the system a "packset", but it later became known as the"walkie-talkie". In 2001, Hings was formally decorated for itssignificance 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 developed the SCR-536's military replacement, the AN/PRC-6. The AN/PRC-6 circuit used 13 vacuum tubes(receiver and transmitter); a second set of 13 tubes was supplied withthe unit as running spares. The unit was factory set with one crystalwhich could be changed to a different frequency in the field byreplacing the crystal and re-tuning the unit. It used a 24 inch whip antenna.There was an optional handset H-33C/PT that could be connected to theAN/PRC-6 by a 5-foot cable. An adjustable strap was provided forcarrying and support while operating.
In the mid-1970s the United States Marine Corps initiated an effort to develop a squadradio to replace the unsatisfactory helmet-mounted AN/PRR-9 receiverand receiver/transmitter hand-held AN/PRT-4 (both developed by the USArmy). The AN/PRC-68 was first produced in 1976 by Magnavox, 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 hamradios, with "walkie-talkie" often used as a layman's term orspecifically to refer to a toy. Public safety or commercial usersgenerally refer to their handhelds simply as "radios". Surplus MotorolaHandie Talkies found their way into the hands of ham radio operatorsimmediately following World War II. Motorola's public safety radios of the 1950s and 1960s, were loaned or donated to ham groups as part of the Civil Defenseprogram. To avoid trademark infringement, other manufacturers usedesignations such as "Handheld Transceiver" or "Handie Transceiver" fortheir products.
Some cellular telephone networksoffer a push-to-talk handset that allows walkie-talkie-like operationover the cellular network, without dialing a call each time. However,the cellphone provider must be accessible.
Walkie-talkies for public safety, commercial and industrial uses may be part of trunked radio systems, which dynamically allocate radio channels for more efficient use of limited radio spectrum. Such systems always work with a base stationthat acts as a repeater and controller, although individual handsetsand mobiles may have a mode that bypasses the base station.
A modern Project 25-capable professional walkie-talkie A Motorola HT1000 two-way radio
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 availableat numerous price points from inexpensive analog units sold as toys upto ruggedized (i.e. waterproof or intrinsically safe)analog and digital units for use on boats or in heavy industry. Mostcountries allow the sale of walkie-talkies for, at least, business, marine communications, and some limited personal uses such as CB radio,as well as for amateur radio designs. Walkie-talkies, thanks toincreasing use of miniaturized electronics, can be made very small, withsome personal two-way UHF radio models being smaller than a deck ofcards (though VHF and HF units can be substantially larger due to theneed for larger antennas and battery packs). In addition, as costs comedown, it is possible to add advanced squelch capabilities such as CTCSS (analog squelch) and DCS(digital squelch) (often marketed as "privacy codes") to inexpensiveradios, as well as voice scrambling and trunking capabilities. Someunits (especially amateur HTs) also include DTMF keypads for remote operation of various devices such as repeaters. Some models include VOX 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 hasonly a few specific frequencies programmed into it (often, though notalways, with a computer or other outside programming device; older unitscan simply swap crystals), since a given business or public safetyagent must often abide by a specific frequency allocation. Consumergear, on the other hand, is generally made to be small, lightweight, andcapable of accessing any channel within the specified band, not just asubset of assigned channels.
Military organizations use handheld radios for a variety of purposes. Modern units such as the AN/PRC-148 Multiband Inter/Intra Team Radio (MBITR) can communicate on a variety of bands and modulation schemes and include encryption capabilities.
Walkie-talkies (also known as HTs or "handheld transceivers") are widely used among amateur radio operators. While converted commercial gear by companies such as Motorola are not uncommon, many companies such as Yaesu, Icom, and Kenwooddesign models specifically for amateur use. While superficially similarto commercial and personal units (including such things as CTCSS andDCS squelch functions, used primarily to activate amateur radio repeaters), 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 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, SSB, and CW, and digital modes such as radioteletype or PSK31. Some may have TNCs built in to support packet radio data transmission without additional hardware.
A newer addition to the Amateur Radio service is Digital Smart Technology for Amateur Radio or D-STAR.Handheld radios with this technology have several advanced features,including narrower bandwidth, simultaneous voice and messaging, GPSposition reporting, and callsign routed radio calls over a wide ranginginternational network.
As mentioned, commercial walkie-talkies can sometimes be reprogrammedto operate on amateur frequencies. Amateur radio operators may do thisfor cost reasons or due to a perception that commercial gear is moresolidly constructed or better designed than purpose-built amateur gear.
The personal walkie-talkie has become popular also because of the U.S. Family Radio Service (FRS) and similar licence-free services (such as Europe's PMR446 and Australia's UHF CB)in other countries. While FRS walkie-talkies are also sometimes used astoys because mass-production makes them low cost, they have proper superheterodynereceivers and are a useful communication tool for both business andpersonal use. The boom in licence-free transceivers has, however, been asource of frustration to users of licensed services that are sometimesinterfered with. For example, FRS and GMRS overlap in the United States, resulting in substantial pirateuse of the GMRS frequencies. Use of the GMRS frequencies (USA) requiresa license; however most users either disregard this requirement or areunaware. Canada reallocated frequencies for licence-free use due toheavy interference from US GMRS users. The European PMR446 channels fallin the middle of a United States UHF amateur allocation, and the US FRSchannels interfere with public safety communications in the UnitedKingdom. Designs for personal walkie-talkies are in any case tightlyregulated, generally requiring non-removable antennas (with a fewexceptions such as CB radio and the United States MURS allocation) and forbidding modified radios.
A Motorola FRS radio
Most personal walkie-talkies sold are designed to operate in UHFallocations, and are designed to be very compact, with buttons forchanging channels and other settings on the face of the radio and ashort, fixed antenna. Most such units are made of heavy, often brightlycolored plastic, though some more expensive units have ruggedized metalor plastic cases. Commercial-grade radios are often designed to be usedon allocations such as GMRS or MURS (the latter of which has had verylittle readily available purpose-built equipment). In addition, CBwalkie-talkies are available, but less popular due to the propagationcharacteristics of the 27 MHz band and the general bulkiness of the gearinvolved.
Personal walkie-talkies are generally designed to give easy access to all available channels (and, if supplied, squelch codes) within the device's specified allocation.
Personal two-way radios are also sometimes combined with other electronic devices; Garmin's Rino series combine a GPS receiverin the same package as an FRS/GMRS walkie-talkie (allowing Rino usersto transmit digital location data to each other) Some personal radiosalso include receivers for AM and FM broadcast radio and, whereapplicable, NOAA Weather Radioand similar systems broadcasting on the same frequencies. Some designsalso allow the sending of text messages and pictures between similarlyequipped units.
While jobsite and government radios are often rated in power output,consumer radios are frequently and controversially rated in mile orkilometer ratings. Because of the line of sightpropagation of UHF signals, experienced users consider such ratings tobe wildly exaggerated, and some manufacturers have begun printing rangeratings on the package based on terrain as opposed to simple poweroutput.
While the bulk of personal walkie-talkie traffic is in the 27 MHz and400-500 MHz area of the UHF spectrum, there are some units that use the"Part 15" 49 MHz band (shared with cordless phones, baby monitors, andsimilar devices) as well as the "Part 15" 900 MHz band; in the US atleast, units in these bands do not require licenses as long as theyadhere to FCC Part 15 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 technology operating in this frequency range under the name eXRS(eXtreme Radio Service—despite the name, a proprietary design, not anofficial allocation of the US FCC). The spread-spectrum scheme used ineXRS radios allows up to 10 billion virtual "channels" and ensuresprivate communications between two or more units.
Low-power versions, exempt from licence requirements, are also popular children's toys such as the Fisher Price Walkie-Talkie for children illustrated in the top image on the right. Prior to the change of CB radio from licensed to "permitted by part" (FCC rules Part 95) status, the typical toy walkie-talkie available in North America was limited to 100 milliwatts of power on transmit and using one or two crystal-controlled channels in the 27 MHzcitizens' band using amplitude modulation (AM) only. Later toy walkie-talkies operated in the 49 MHz band, some with frequency modulation (FM), shared with cordless phones and baby monitors. The lowest cost devices are very simple electronically (single-frequency, crystal-controlled, generally based on a simple discrete transistor circuit where "grown-up" walkie-talkies use chips), may employ superregenerativereceivers, and may lack even a volume control, but they maynevertheless be elaborately decorated, often superficially resemblingmore "grown-up" radios such as FRS or public safety gear. Unlike morecostly units, low-cost toy walkie-talkies may not have separatemicrophones and speakers; the receiver's speaker sometimes doubles as amicrophone while in transmit mode.
An inexpensive children's walkie-talkie
An unusual feature, common on children's walkie-talkies but seldomavailable otherwise even on amateur models, is a "code key", that is, abutton allowing the operator to transmit Morse codeor similar tones to another walkie-talkie operating on the samefrequency. Generally the operator depresses the PTT button and taps out amessage using a Morse Code crib sheetattached as a sticker to the radio; however, as Morse Code has fallenout of wide use outside amateur radio circles, some such units eitherhave a grossly simplified code label or no longer provide a sticker atall.
In addition, personal UHF radios will sometimes be bought and used astoys, though they are not generally explicitly marketed as such (butsee Hasbro's ChatNow line, which transmits both voice and digital data on the FRS band).
Smartphone apps & connected devices
A variety of mobile apps exist that mimic a walkie-talkie/Push-to-talkstyle interaction. They are marketed as low-latency, asynchronouscommunication. The advantages touted over two-way voice calls include:the asynchronous nature not requiring full user interaction (like SMS) and it is voice over IP (VOIP) so it does not use minutes on a cellular plan.
Applications on the market that offer this walkie-talkie style interaction for audio include Voxer, Zello, Orion Labs, Motorola Wave, and HeyTell, among others.
Other smartphone-based walkie-talkie products are made by companies like goTenna, Fantom Dynamics and BearTooth,and offer a radio interface. Unlike mobile data dependent applications,these products work by pairing to an app on the user’s smartphone andworking over a radio interface. These products are consumer orientedimplementations of technologies that have been widely available to HAMradio enthusiasts for years.