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B-Netz
B-Netz was an analog, commercial mobile radio telephone network that was operated by the Deutsche Bundespost in Germany (at first only West Germany) from 1972 until 1994. The system was also implemented in neighboring countries Austria, The Netherlands and Luxembourg. The B refers to the fact that it was the country's second public mobile telephone network, following the A-Netz. As opposed to its predecessor, it featured direct-dialing (so that human operators were not required to connect calls). The frequency plan originally included only 38 channels (with one call possible per frequency channel), but it was upgraded to incorporate the A-Netz frequencies when that network was retired in 1980. The upgraded network had 78 channels and is sometimes referred to as the B2-Netz. A major limitation of system was that, in order to reach a subscriber, one had to know his location since the handset would assume the local area code of the base station serving it. Handoff was not possible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
C-Netz
The Radio Telephone Network C (German: Funktelefonnetz-C, abbreviated as C-Netz), was a first generation analog cellular phone system deployed and operated in Germany (at first West Germany) by DeTeMobil (formerly of Deutsche Bundespost Telekom, currently Deutsche Telekom). It utilized the C-450 standard, originally developed by Siemens AG, and was the third and last update of a series of analog mobile phone systems used primarily within Germany, superseding the B-Netz and the A-Netz before it. It has been decommissioned, replaced by both the newer ''D-Netz'' and ''E-Netz'' systems, both based on GSM standards (which are digital) and operating on 900 MHz and 1800 MHz bands respectively. C-Netz was active from 1985 to 2000, with certain areas until 2001. Since then, all consumer cellular phone services in Germany are digital-only. The dialing code for the C-Netz was 0161, which is no longer in use. As a result, users were not able to transfer their numbers to GSM n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobile Radio Telephone
Mobile radio telephone systems were telephone systems of a wireless type that preceded the modern cellular mobile form of telephony 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Analog Signal
An analog signal or analogue signal (see spelling differences) is any continuous signal representing some other quantity, i.e., ''analogous'' to another quantity. For example, in an analog audio signal, the instantaneous signal voltage varies continuously with the pressure of the sound waves. In contrast, a digital signal represents the original time-varying quantity as a sampled sequence of quantized values which imposes some bandwidth and dynamic range constraints on the representation. The term ''analog signal'' usually refers to electrical signals; however, mechanical, pneumatic, hydraulic and other systems may also convey or be considered analog signals. Representation An analog signal uses some property of the medium to convey the signal's information. For example, an aneroid barometer uses rotary position as the signal to convey pressure information. In an electrical signal, the voltage, current, or frequency of the signal may be varied to represent the information. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duplex (telecommunications)
A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow for simultaneous communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field. There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX). In a full-duplex system, both parties can communicate with each other simultaneously. An example of a full-duplex device is plain old telephone service; the parties at both ends of a call can speak and be heard by the other party simultaneously. The earphone reproduces the speech of the remote party as the microphone transmits the speech of the local party. There is a two-way communication channel between them, or more strictly speaking, there are two communication channel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Channel Spacing
Channel spacing, also known as bandwidth, is a term used in radio frequency planning. It describes the frequency difference between adjacent allocations in a frequency plan. Channels for mediumwave Medium wave (MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. During the dayti ... radio stations, for example are allocated in internationally agreed steps of 9 or 10 kHz: 10 kHz in ITU Region 2 (the Americas) and 9 kHz elsewhere in the world. References Broadcast engineering {{Radio-comm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bandwidth (signal Processing)
Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies. It is typically measured in hertz, and depending on context, may specifically refer to ''passband bandwidth'' or ''baseband bandwidth''. Passband bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a band-pass filter, a communication channel, or a signal spectrum. Baseband bandwidth applies to a low-pass filter or baseband signal; the bandwidth is equal to its upper cutoff frequency. Bandwidth in hertz is a central concept in many fields, including electronics, information theory, digital communications, radio communications, signal processing, and spectroscopy and is one of the determinants of the capacity of a given communication channel. A key characteristic of bandwidth is that any band of a given width can carry the same amount of information, regardless of where that band is located in the frequency spectrum. For example, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Division Multiplexing
In telecommunications, frequency-division multiplexing (FDM) is a technique by which the total bandwidth available in a communication medium is divided into a series of non-overlapping frequency bands, each of which is used to carry a separate signal. This allows a single transmission medium such as a microwave radio link, cable or optical fiber to be shared by multiple independent signals. Another use is to carry separate serial bits or segments of a higher rate signal in parallel. The most common example of frequency-division multiplexing is radio and television broadcasting, in which multiple radio signals at different frequencies pass through the air at the same time. Another example is cable television, in which many television channels are carried simultaneously on a single cable. FDM is also used by telephone systems to transmit multiple telephone calls through high capacity trunklines, communications satellites to transmit multiple channels of data on uplink and downl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiplexing
In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a physical transmission medium. For example, in telecommunications, several telephone calls may be carried using one wire. Multiplexing originated in telegraphy in the 1870s, and is now widely applied in communications. In telephony, George Owen Squier is credited with the development of telephone carrier multiplexing in 1910. The multiplexed signal is transmitted over a communication channel such as a cable. The multiplexing divides the capacity of the communication channel into several logical channels, one for each message signal or data stream to be transferred. A reverse process, known as demultiplexing, extracts the original channels on the receiver end. A device that performs the multiplexing is called a multiplexer (MUX), and a dev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eavesdropping
Eavesdropping is the act of secretly or stealthily listening to the private conversation or communications of others without their consent in order to gather information. Etymology The verb ''eavesdrop'' is a back-formation from the noun ''eavesdropper'' ("a person who eavesdrops"), which was formed from the related noun ''eavesdrop'' ("the dripping of water from the eaves of a house; the ground on which such water falls"). An eavesdropper was someone who would hang from the eave of a building so as to hear what is said within. The PBS documentaries ''Inside the Court of Henry VIII'' (April 8, 2015) and ''Secrets of Henry VIII’s Palace'' (June 30, 2013) include segments that display and discuss "eavedrops", carved wooden figures Henry VIII had built into the eaves (overhanging edges of the beams in the ceiling) of Hampton Court to discourage unwanted gossip or dissension from the King's wishes and rule, to foment paranoia and fear, and demonstrate that everything said there was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Encryption
In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decipher a ciphertext back to plaintext and access the original information. Encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor. For technical reasons, an encryption scheme usually uses a pseudo-random encryption key generated by an algorithm. It is possible to decrypt the message without possessing the key but, for a well-designed encryption scheme, considerable computational resources and skills are required. An authorized recipient can easily decrypt the message with the key provided by the originator to recipients but not to unauthorized users. Historically, various forms of encryption have been used to aid in cryptography. Early encryption techniques were often used in military ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erlang Unit
The erlang (symbol E) is a dimensionless unit that is used in telephony as a measure of offered load or carried load on service-providing elements such as telephone circuits or telephone switching equipment. A single cord circuit has the capacity to be used for 60 minutes in one hour. Full utilization of that capacity, 60 minutes of traffic, constitutes 1 erlang. Carried traffic in erlangs is the average number of concurrent calls measured over a given period (often one hour), while offered traffic is the traffic that would be carried if all call-attempts succeeded. How much offered traffic is carried in practice will depend on what happens to unanswered calls when all servers are busy. The CCITT named the international unit of telephone traffic the erlang in 1946 in honor of Agner Krarup Erlang. In Erlang's analysis of efficient telephone line usage he derived the formulae for two important cases, Erlang-B and Erlang-C, which became foundational results in teletraffic engineer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West Berlin
West Berlin (german: Berlin (West) or , ) was a political enclave which comprised the western part of Berlin during the years of the Cold War. Although West Berlin was de jure not part of West Germany, lacked any sovereignty, and was under military occupation until German reunification in 1990, the territory was claimed by the West Germany, Federal Republic of Germany (FRG) which was heavily disputed by the Soviet Union and other Eastern Bloc countries. However, West Berlin de facto aligned itself politically with the FRG on 23 May 1949, was directly or indirectly represented in its federal institutions, and most of its residents were citizens of the FRG. West Berlin was formally controlled by the Western Allies and entirely surrounded by the Soviet Union, Soviet-controlled East Berlin and East Germany. West Berlin had great symbolic significance during the Cold War, as it was widely considered by westerners an "island of free world, freedom" and America's most loyal counterpa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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