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A walkie-talkie (more formally known as a handheld transceiver, or HT) is a hand-held, portable, two-way radio transceiver. 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 field artillery and tank units, and after the war, walkie-talkies spread to public safety and eventually commercial and jobsite work.

Typical walkie-talkies resemble a telephone handset, 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-duplex communication device. Multiple walkie-talkies use a single radio channel, and only one radio on the channel can transmit at a time, although any number can listen. The transceiver is normally in receive mode; when the user wants to talk they must press a "push-to-talk" (PTT) button that turns off the receiver and turns on the transmitter.

Canadian inventor Donald Hings was the first to create a portable radio signaling system for his employer CM&S in 1937. He called the system a "packset", although it later became known as a "walkie-talkie". In 2001, Hings was formally decorated for the device's significance to the war effort. Hings' model C-58 "Handy-Talkie" was in military service by 1942, the result of a secret R&D effort that began in 1940.

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 between 1938 and 1941, and is sometimes credited with inventing it.

The first device to be widely nicknamed a "walkie-talkie" was developed by the US military during World War II, the backpacked Motorola SCR-300. It was created by an engineering team in 1940 at the Galvin Manufacturing Company (forerunner 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.

The first handheld walkie-talkie was the AM SCR-536 transceiver from 1941, also made by Motorola, named 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. Both devices used vacuum tubes and were powered by high voltage dry cell batteries.

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 thirteen tubes was supplied with the unit as running spares. The unit was factory set with one crystal which could be changed to a different frequency in the field by replacing the crystal and re-tuning the unit. It used a 24-inch whip antenna. There was an optional handset that could be connected to the AN/PRC-6 by a 5-foot cable. An adjustable strap was provided for carrying and support while operating.

In the mid-1970s, the United States Marine Corps initiated an effort to develop a squad radio to replace the unsatisfactory helmet-mounted AN/PRR-9 receiver and receiver/transmitter handheld AN/PRT-4 (both developed by the US Army). The AN/PRC-68, 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 ham radios, with "walkie-talkie" often used as a layman's term or specifically to refer to a toy. Public safety and 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. Motorola's public safety radios of the 1950s and 1960s were loaned or donated to ham groups as part of the Civil Defense program. To avoid trademark infringement, other manufacturers use designations such as "Handheld Transceiver" or "Handie Transceiver" for their products.

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 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 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 capabilities such as CTCSS (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 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 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.

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