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One-way Voice Link
A one-way voice link (OWVL) is typically a radio based communication method used by spy networks to communicate with agents in the field typically (but not exclusively) using shortwave radio frequencies. Shortwave frequencies were and are generally highly preferred for their long range, as a communications link of 1200 km is easily possible. VHF and UHF frequencies can be used for one-way voice circuits, but are generally not preferred as their range is at best 300 km (on flat terrain). Since the 1970s infrared point-to-point communication systems have been used that offer OWVLs, but the number of users was always limited. This communications system often employs recorders to transmit pre-recorded messages in real time or in burst transmissions, which minimize the time that a spy needs to be on the air. Voice-scrambling systems have been selectively used for this kind of communications circuit since the 1980s, based on operational needs. Since personal computers b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shortwave Radio
Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 metres); above the medium frequency band (MF), to the bottom of the VHF band. Radio waves in the shortwave band can be reflected or refracted from a layer of electrically charged atoms in the atmosphere called the ionosphere. Therefore, short waves directed at an angle into the sky can be reflected back to Earth at great distances, beyond the horizon. This is called skywave or "skip" propagation. Thus shortwave radio can be used for communication over very long distances, in contrast to radio waves of higher frequency, which travel in straight lines ( line-of-sight propagation) and are limited by the visual horizon, about 64 km (40 miles). Shortwave broadcasts of radio programs played an important role in the early days of radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burst Transmission
In telecommunication, a burst transmission or data burst is the broadcast of a relatively high-bandwidth transmission over a short period. Burst transmission can be intentional, broadcasting a compressed message at a very high data signaling rate within a very short transmission time. In the 1980s, the term "data burst" (and "info burst") was used for a technique used by some United Kingdom and South African TV programmes to transmit large amounts of primarily textual information. They would display multiple pages of text in rapid succession, usually at the end of the programme; viewers would videotape it and then read it later by playing it back using the pause button after each page. Data bursts can occur naturally, such as when the download of data from the internet briefly experiences higher speeds. It can also occur in a computer network where data transmission is interrupted at intervals. Burst transmission enables communications between data terminal equipment (DTEs) and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NICAM
Near Instantaneous Companded Audio Multiplex (NICAM) is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks.Croll, M.G., Osborne, D.W. and Spicer, C.R. (1974), ''Digital sound signals: the present BBC distribution system and a proposal for bit-rate reduction by digital companding''. IEE Conference publication No. 119, pp. 90–96 In the 1980s, broadcasters began to use NICAM compression for transmissions of stereo TV sound to the public. History Near-instantaneous companding The idea was first described in 1964. In this, the 'ranging' was to be applied to the analogue signal before the analogue-to-digital converter (ADC) and after the digital-to-analogue converter (DAC). The application of this to broadcasting, in which the companding was to be done entirely digitally after the ADC and before the DAC, was described in a 1972 BBC Research Report. Point-to-point links NI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cold War
The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because there was no large-scale fighting directly between the two superpowers, but they each supported major regional conflicts known as proxy wars. The conflict was based around the ideological and geopolitical struggle for global influence by these two superpowers, following their temporary alliance and victory against Nazi Germany and Imperial Japan in 1945. Aside from the nuclear arsenal development and conventional military deployment, the struggle for dominance was expressed via indirect means such as psychological warfare, propaganda campaigns, espionage, far-reaching embargoes, rivalry at sports events, and technological competitions such as the Space Race. The Western Bloc was led by the United States as well as a number of other First W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
STASI
The Ministry for State Security, commonly known as the (),An abbreviation of . was the Intelligence agency, state security service of the East Germany from 1950 to 1990. The Stasi's function was similar to the KGB, serving as a means of maintaining state authority, i.e., the "Sword and Shield of the Party" (). This was accomplished primarily through the use of a network of civilian informants. This organization contributed to the arrest of approximately 250,000 people in East Germany. The Stasi also conducted espionage and other clandestine operations abroad through its subordinate foreign intelligence service, the Main Directorate for Reconnaissance, Office of Enlightenment, or Head Office A (german: Hauptverwaltung Aufklärung). They also maintained contacts and occasionally cooperated with West German terrorists. The Stasi was headquartered in East Berlin, with an extensive complex in Lichtenberg (locality), Berlin-Lichtenberg and several smaller facilities throughout the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Falklands War
The Falklands War ( es, link=no, Guerra de las Malvinas) was a ten-week undeclared war between Argentina and the United Kingdom in 1982 over two British dependent territories in the South Atlantic: the Falkland Islands and its territorial dependency, South Georgia and the South Sandwich Islands. The conflict began on 2 April, when Argentina invaded and occupied the Falkland Islands, followed by the invasion of South Georgia the next day. On 5 April, the British government dispatched a naval task force to engage the Argentine Navy and Air Force before making an amphibious assault on the islands. The conflict lasted 74 days and ended with an Argentine surrender on 14 June, returning the islands to British control. In total, 649 Argentine military personnel, 255 British military personnel, and three Falkland Islanders were killed during the hostilities. The conflict was a major episode in the protracted dispute over the territories' sovereignt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Numbers Station
A numbers station is a shortwave radio station characterized by broadcasts of formatted numbers, which are believed to be addressed to intelligence officers operating in foreign countries. Most identified stations use speech synthesis to vocalize numbers, although digital modes such as phase-shift keying and frequency-shift keying, as well as Morse code transmissions, are not uncommon. Most stations have set time schedules, or schedule patterns; however, other stations appear to have no discernible pattern and broadcast at unpredictable times. Stations may or may not have set frequencies in the high frequency band. The first known use of numbers stations was during World War I, with the numbers transmitted in Morse code. Numbers stations were most prolific during the Cold War era, yet many continue to broadcast and some long-time stations may have been taken over by different operators. The Czech Ministry of the Interior and the Swedish Security Service have both acknowledged ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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