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A walkie-talkie (also known as handheld transceiver) is a hand-held, portable, two-way radio transceiver (duplex system). Its development can be traced back around the Second World War and has been credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola. Similar designs were created for other armed forces, and after the war, walkie-talkies spread to public safety and eventually commercialized into jobsite work. Major characteristics include a half-duplex channel (only one radio transmits at a time, though any number can listen) and a "push-to-talk" (PTT) switch that starts transmission. Typical walkie-talkies resemble a telephone handset, possibly slightly larger but still a single unit, with an antenna sticking out of the top. Whereas 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.
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A complete single-conversion FM receiver using the MC3367 is shown as in figure. This IC is designed for use in low powered NBFM transmitter/receivers, called transceivers or walkie-talkies, which are usually battery powered. The IC contains a mixer, LO, two IF amplifiers, limiters, and a quadrature detector, plus an audio amplifier for the final output to headphones or a smaller speaker. It also contains a data buffer and a data comparator, which can be used to properly filter and amplify data (not voice) for applications where the modulating signal is in binary form representing letters and numbers that are received and then displayed to the user . The RF frequency to the mixer can be up to 75MHz, and only one inductor, a few capacitors and resistors, and two 455-kHz IF filters are needed external to the IC. The mixer may be preceded by an RF amplifier, if necessary, although the sensitivity of 0.2µV for – 3-dB limiting is sufficient for many applications.
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For maximum flexibility, the LO frequency can be set by either a lower-cost LC circuit or a more stable crystal. The mixer output IF is 455kHz, which means that this IC should be used only where image signals are not a problem. If there may be a problem, a dual-conversion design should be used, with a first conversion stage ahead of this stage at a higher IF, such as 10.7 MHz, which then feeds into the MC3367. There is a low-voltage detector circuit built in, which monitors the battery voltage and signals if the voltage drops below the level needed for proper operation of the rest of the IC. The entire single-conversion FM receiver function requires only 1.1 to 3.0 V at a current of less than 3 mA (not counting the current driving the audio output). This makes the MC3367 ideal for radios that will be on continuously and monitoring relatively quiet channels for transmissions, such as police and public-safety and walkie-talkies, or pages and beepers.
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In addition to land mobile use, walkie-talkie designs are also used for marine VHF and aviation 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 vapours. This designation means that the knobs and switches in the radio are engineered to avoid producing sparks as they are operated.

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 Talkie for military purpose (AN/PRC-148). The AN/PRC-148 Multiband Inter/Intra Team Radio (MBITR) is the most widely fielded handheld multiband, tactical software-defined radio, in use with the US Military and NATO forces around the world. The radio is built by Thales Communications, a subsidiary of the Thales Group. The designation AN/PRC translates to Army/Navy Portable Radio used for two way Communications, according to Joint Electronics Type Designation System guidelines. The MBITR was developed by USSOCOM and Thales Communications in the 1990s and went into production in 2000, to address the need for a secure multiband handheld radio. As the US Army realized the benefits of the system it began wider deployment with Stryker Combat Teams and then with troops deploying to Iraq and Afghanistan. As of August 2007, 100,000 MBITRs have been fielded, over 31,000 of which are in use by the US Army.