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IMTS Frequencies
The Improved Mobile Telephone Service (IMTS) was a pre-Cellular network, cellular Very High Frequency, VHF/Ultra High Frequency, UHF radio system which linked to the Public Switched Telephone Network, public telephone network. IMTS was the radiotelephone equivalent of Landline, land dial phone service. Introduced in 1964, it replaced Mobile Telephone Service (MTS) and improved on most MTS systems by offering direct-dial rather than connections through a live operator, and Duplex (telecommunications)#Full duplex, full-duplex operation so both parties could talk at the same time. Technical Information The original Bell System US and Canadian mobile telephone system includes three frequency bands, VHF Low (35-44 MHz, 9 channels), VHF High (152-158 MHz, 11 channels in the U.S., 13 channels in Canada), and UHF (454-460 MHz, 12 channels). Alternative names were "Low Band", "High band" and "UHF". In addition to the Bell system (wireline incumbent) channels, another 7 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Co-channel Interference
Co-channel interference or CCI is crosstalk from two different radio transmitters using the same channel. Co-channel interference can be caused by many factors from weather conditions to administrative and design issues. Co-channel interference may be controlled by various radio resource management schemes. Cellular mobile networks In cellular mobile communication (GSM & LTE Systems, for instance), frequency spectrum is a precious resource which is divided into non-overlapping spectrum bands which are assigned to different cells (In cellular communications, a cell refers to the hexagonal/circular area around the base station antenna). However, after certain geographical distance, these frequency bands are re-used, i.e. the same spectrum bands are reassigned to other distant cells. The co-channel interference arises in the cellular mobile networks owing to this phenomenon of frequency reuse. Thus, besides the intended signal from within the cell, signals at the same freque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Two-way Radio
A two-way radio is a radio transceiver (a radio that can both transmit and receive radio waves), which is used for bidirectional person-to-person voice communication with other users with similar radios, in contrast to a broadcast receiver, which only receives transmissions. Two-way radios usually use a half-duplex communication channel, which permits two-way communication, albeit with the limitation that only one user can transmit at a time. (This is in contrast to simplex communication, in which transmission can only be sent in one direction, and full-duplex, which allows transmission in both directions simultaneously.) This requires users in a group to take turns talking. The radio is normally in receive mode so the user can hear all other transmissions on the channel. When the user wants to talk, they press a " push-to-talk" button, which turns off the receiver and turns on the transmitter; when the button is released, the receiver is activated again. Multiple channels are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiotelephone
A radiotelephone (or radiophone), abbreviated RT, is a radio communication system for conducting a conversation; radiotelephony means telephony by radio. It is in contrast to ''radiotelegraphy'', which is radio transmission of telegrams (messages), or ''television'', transmission of video, moving pictures and sound. The term is related to radio broadcasting, which transmit audio one way to listeners. Radiotelephony refers specifically to two-way radio systems for bidirectional person-to-person voice communication between separated users, such as CB radio or marine radio. In spite of the name, radiotelephony systems are not necessarily connected to or have anything to do with the public switched telephone network, telephone network, and in some radio services, including General Mobile Radio Service, GMRS, interconnection is prohibited. Design Mode of emission The word ''phone'' has a long precedent beginning with early US wired voice systems. The term means ''voice'' as oppos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Radio Telephone
Mobile radio telephone systems were mobile telephony systems that preceded modern cellular network technology. Since they were the predecessors of the first generation of cellular telephones, these systems are sometimes retroactively referred to as pre-cellular (or sometimes zero generation, that is, 0G) systems. Technologies used in pre-cellular systems included the Push-to-talk (PTT or manual), Mobile Telephone Service (MTS), Improved Mobile Telephone Service (IMTS), and Advanced Mobile Telephone System (AMTS) systems. These early mobile telephone systems can be distinguished from earlier closed radiotelephone systems in that they were available as a commercial service that was part of the public switched telephone network, with their own telephone numbers, rather than part of a closed network such as a police radio or taxi dispatching system. These mobile telephones were usually mounted in cars or trucks (thus called ''car phones''), although portable briefcase models we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Car Phone
A car phone is a mobile radio telephone specifically designed for and fitted into an automobile. This service originated with the Bell System and was first used in St. Louis, Missouri, on June 17, 1946. Overview United States The original equipment weighed , and there were initially only three channels for all the users in the metropolitan area (other sources claim six channels). On October 2, 1946, Motorola communications equipment carried the first calls on Illinois Bell Telephone Company's new car radiotelephone service in Chicago. Due to the small number of radio frequencies available, the service quickly reached capacity. In 1964 AT&T introduced the Improved Mobile Telephone Service (IMTS). More licenses were added, bringing the total to 32 channels across three bands (See IMTS frequencies). This service was used at least into the 1980s in large portions of North America. In 1968, almost 22 years after the initial network, the US government started to consider reservin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advanced Mobile Phone System
Advanced Mobile Phone System (AMPS) was an analog mobile phone system standard originally developed by Bell Labs and later modified in a cooperative effort between Bell Labs and Motorola. It was officially introduced in the Americas on October 13, 1983,Private Line and was deployed in many other countries too, including Israel in 1986, Australia in 1987, Singapore in 1988, and Pakistan in 1990. It was the primary analog mobile phone system in North America (and other locales) through the 1980s and into the 2000s. As of February 18, 2008, carriers in the United States were no longer required to support AMPS and companies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CB Radio
Citizens band radio (CB radio) is a land mobile radio system, a system allowing short-distance one-to-many bidirectional voice communication among individuals, using two-way radios operating near 27 MHz (or the 11-m wavelength) in the high frequency or shortwave band. Citizens band is distinct from other personal radio service allocations such as FRS, GMRS, MURS, UHF CB and the Amateur Radio Service ( "ham" radio). In many countries, CB operation does not require a license and may be used for business or personal communications. Like many other land mobile radio services, multiple radios in a local area share a single frequency channel, but only one can transmit at a time. The radio is normally in receive mode to receive transmissions of other radios on the channel; when users want to communicate they press a "push to talk" button on their radio, which turns on their transmitter. Users on a channel must take turns transmitting. In the US and Canada, and in the EU and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whip Antenna
A whip antenna is an antenna consisting of a straight flexible wire or rod. The bottom end of the whip is connected to the radio receiver or transmitter. A whip antenna is a form of monopole antenna. The antenna is designed to be flexible so that it does not break easily, and the name is derived from the whip-like motion that it exhibits when disturbed. Whip antennas for portable radios are often made of a series of interlocking telescoping metal tubes, so they can be retracted when not in use. Longer whips, made for mounting on vehicles and structures, are made of a flexible fiberglass rod around a wire core and can be up to long. The length of a whip antenna is determined by the wavelength of the radio waves it is used with. Their length varies from compact electrically short antennas wavelength long, up to wavelength to improve directivity. The most common type is the ''quarter-wave whip'', which is approximately long. Whips are the most common type o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Numbering Plan
The North American Numbering Plan (NANP) is an integrated telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1, World Numbering Zone 1 and has the telephone country code, country code ''1''. Some North American countries, most notably Telephone numbers in Mexico, Mexico, do not participate in the NANP. The concepts of the NANP were devised originally during the 1940s by the American Telephone and Telegraph Company (AT&T) for the Bell System and the independent telephone companies in North America in Operator Toll Dialing. The first task was to unify the diverse local telephone numbering plans that had been established during the preceding decades, with the goal to speed call completion times and decrease the costs for long-distance calling, by reducing manual labor by switchboard operators. Eventually, it prepared the continent for direct-dialing of long-distance calls ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pagers
A pager, also known as a beeper or bleeper, is a wireless telecommunications device that receives and displays alphanumeric or voice messages. One-way pagers can only receive messages, while response pagers and two-way pagers can also acknowledge, reply to, and originate messages using an internal transmitter. Pagers operate as part of a paging system which includes one or more fixed transmitters (or in the case of response pagers and two-way pagers, one or more base stations), as well as a number of pagers carried by mobile users. These systems can range from a restaurant system with a single low power transmitter, to a nationwide system with thousands of high-power base stations. Pagers were developed in the 1950s and 1960s, and became widely used by the 1980s through the late 1990s and early 2000s. Later in the 21st century, the widespread availability of cellphones and smartphones with text messaging capability has greatly diminished the pager industry. Nevertheless ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cellular Network
A cellular network or mobile network is a telecommunications network where the link to and from end nodes is wireless network, wireless and the network is distributed over land areas called ''cells'', each served by at least one fixed-location transceiver (such as a base station). These base stations provide the cell with the network coverage which can be used for transmission of voice, data, and other types of content via radio waves. Each cell's coverage area is determined by factors such as the power of the transceiver, the terrain, and the frequency band being used. A cell typically uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed service quality within each cell. When joined together, these cells provide radio coverage over a wide geographic area. This enables numerous Mobile device, devices, including mobile phones, Tablet computer, tablets, laptops equipped with mobile broadband modems, and Wearable technology, wea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
