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This requires either two separate radio channels or channel sharing methods such as time-division duplex (TDD) to carry the two directions of the conversation simultaneously on a single radio frequency. [2] The first two-way radio was an AM-only device introduced by the Galvin Manufacturing Corporation in 1940 for use by the police and military ...
The Private Land Mobile Radio Service (47CFR90, or Part 90 of the FCC Rules) was established in the US in 1927 [3] to permit commercial and public safety uses of two-way radio by commercial entities and non-Federal government agencies. Similar allocations are available in other countries.
The General Mobile Radio Service (GMRS) is a land-mobile FM UHF radio service designed for short-range two-way voice communication and authorized under part 95 of the US FCC code. It requires a license in the United States, but some GMRS compatible equipment can be used license-free in Canada. The US GMRS license is issued for a period of 10 years.
Forest Industries Telecommunications (FIT) is a Federal Communications Commission (FCC) certified frequency coordinator [1] and a non-profit association. Established in 1947, [2] its members include those companies or individuals who employ or are eligible to use Land Mobile Radio Service (LMRS) two-way radios.
Several hand-held Project 25 radios used around the world. Project 25 (P25 or APCO-25) is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. [1]
Radio waves are defined by the ITU as: "electromagnetic waves of frequencies arbitrarily lower than 3000 GHz, propagated in space without artificial guide". [5] At the high frequency end the radio spectrum is bounded by the infrared band. The boundary between radio waves and infrared waves is defined at different frequencies in different ...
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Specific frequency allocations vary from country to country and between ITU regions as specified in the current ITU HF frequency allocations for amateur radio. [1] The list of frequency ranges is called a band allocation, which may be set by international agreements, and national regulations. The modes and types of allocations within each ...