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Thing (listening Device)
Replica of The Thing which contained a Soviet bugging device, on display at the National_Cryptologic_Museum.html" ;"title="NSA's National Cryptologic Museum">NSA's National Cryptologic Museum The Thing, also known as the Great Seal bug, was one of the first covert listening devices (or "bugs") to use passive techniques to transmit an audio signal. It was concealed inside a gift given by the Soviet Union to W. Averell Harriman, the United States Ambassador to the Soviet Union, on August 4, 1945. Because it was passive, needing electromagnetic energy from an outside source to become energized and active, it is considered a predecessor of radio-frequency identification (RFID) technology. The Thing consisted of a tiny capacitive membrane connected to a small quarter-wavelength antenna; it had no power supply or active electronic components. The device, a passive cavity resonator, became active only when a radio signal of the correct frequency was sent to the device from an exter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inductance
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The electric current produces a magnetic field around the conductor. The magnetic field strength depends on the magnitude of the electric current, and therefore follows any changes in the magnitude of the current. From Faraday's law of induction, any change in magnetic field through a circuit induces an electromotive force (EMF) (voltage) in the conductors, a process known as electromagnetic induction. This induced voltage created by the changing current has the effect of opposing the change in current. This is stated by Lenz's law, and the voltage is called ''back EMF''. Inductance is defined as the ratio of the induced voltage to the rate of change of current causing it. It is a proportionality constant that depends on the geometry of circuit conductors (e.g., cross-section area and length) and the magnetic permeability of the conductor and nearby materials. An ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks in World War II, Tanks and Air warfare of World War II, aircraft played major roles, enabling the strategic bombing of cities and delivery of the Atomic bombings of Hiroshima and Nagasaki, first and only nuclear weapons ever used in war. World War II is the List of wars by death toll, deadliest conflict in history, causing World War II casualties, the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Allied-occupied Germany, Germany, Allied-occupied Austria, Austria, Occupation of Japan, Japan, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Government Of The Soviet Union
The Government of the Union of Soviet Socialist Republics (USSR) was the executive and administrative organ of the highest organ of state power, highest body of state authority, the Supreme Soviet of the Soviet Union, All-Union Supreme Soviet. It was formed on 30 December 1922 and abolished on 26 December 1991. The government was headed by a chairman, most commonly referred to as the premier of the Soviet Union, and several Deputy Premier of the Soviet Union, deputy chairmen throughout its existence. The Communist Party of the Soviet Union (CPSU), as "Leading role of the party, The leading and guiding force of Soviet society and the nucleus of its political system" per Article 6 of the 1977 Constitution of the Soviet Union, state constitution, controlled the government by holding a two-thirds majority in the All-Union Supreme Soviet. The government underwent several name changes throughout its history, and was known as the Council of People's Commissars of the Soviet Union, Council ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theremin
The theremin (; originally known as the ætherphone, etherphone, thereminophone or termenvox/thereminvox) is an electronic musical instrument controlled without physical contact by the performer (who is known as a thereminist). It is named after its inventor, Leon Theremin, who patented the device in 1928. The instrument's controlling section usually consists of two metal antennas which function not as radio antennas but rather as position sensors. Each antenna forms one half of a capacitor with each of the thereminist's hands as the other half of the capacitor. These antennas capacitively sense the relative position of the hands and control oscillators for frequency with one hand, and amplitude (volume) with the other. The electric signals from the theremin are amplified and sent to a loudspeaker. The sound of the instrument is often associated with eerie situations. The theremin has been used in movie soundtracks such as Miklós Rózsa's '' Spellbound'' and '' Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leon Theremin
Lev Sergeyevich Termen ( 18963 November 1993), better known as Leon Theremin, was a Russian inventor, most famous for his invention of the theremin, one of the first electronic musical instruments and the first to be mass-produced. He also worked on early television research. His secret listening device, " The Thing", hung for seven years in plain view in the United States ambassador's Moscow office and enabled Soviet agents to eavesdrop on secret conversations. Early life Leon Theremin was born in Saint Petersburg, Russian Empire in 1896. His father was Sergei Emilievich Theremin, of French Huguenot descent. His mother was Yevgenia Antonova Orzhinskaya and of German ancestry. He had a sister named Helena. In the seventh grade of his high school, in front of an audience of students and parents, he demonstrated various optical effects using electricity. By the age of 17 he was in his last year of high school, had his own laboratory at home for experimenting with high-frequenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Board (music)
In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the brain. Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of to . Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges, allowing some to even hear ultrasounds. Definition Sound is defined as "(a) Oscillation in pressure, stress, particle displacement, particle velocity, etc., propagated in a medium with internal forces (e.g., elastic or viscous), or the superposition of such propagated oscillation. (b) Auditory sensat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Seal Of The United States
The Great Seal is the seal of the United States. The phrase is used both for the Seal (emblem), impression device itself, which is kept by the United States secretary of state, and more generally for the impression it produces. The Obverse and reverse, obverse of the Great Seal depicts the national coat of arms of the United States while the reverse features a truncated pyramid topped by an Eye of Providence. The year of the U.S. Declaration of Independence, 1776, is noted in Roman numerals at the base of the pyramid. The seal contains three Latin phrases: ''E Pluribus Unum'' ("Out of many, one"), ''Annuit cœptis'' ("He has favored our undertakings"), and ''Novus ordo seclorum'' ("A new order of the ages"). Largely designed by Charles Thomson, secretary of the Continental Congress, and William Barton (heraldist), William Barton, and first used in 1782, the seal is used to authenticate certain documents issued by the federal government of the United States. Since 1935, both sides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United Business Media
UBM plc was a British business-to-business (B2B) events organiser headquartered in London, England, before its acquisition by Informa in 2018. It had a long history as a Multinational corporation, multinational media company. Its main focus was on B2B events, but its principal operations included live media and business-to-business communications, marketing services and data provision, and it principally served the technology, healthcare, trade and transport, ingredients and fashion industries. UBM was listed on the London Stock Exchange and was a constituent of the FTSE 250 Index. History Newspaper interests The history of the companies that made up UBM stretches back almost two hundred years. Up until its acquisition UBM businesses published many titles that were launched in the 19th century, including ''Building'' magazine, launched in 1843 by Joseph Hansom, as well as ''Chemist & Druggist''. The company was founded in 1918 as United Newspapers by David Lloyd George to acqu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harmonic
In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the ''fundamental frequency'' of a periodic signal. The fundamental frequency is also called the ''1st harmonic''; the other harmonics are known as ''higher harmonics''. As all harmonics are periodic at the fundamental frequency, the sum of harmonics is also periodic at that frequency. The set of harmonics forms a '' harmonic series''. The term is employed in various disciplines, including music, physics, acoustics, electronic power transmission, radio technology, and other fields. For example, if the fundamental frequency is 50 Hz, a common AC power supply frequency, the frequencies of the first three higher harmonics are 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), 200 Hz (4th harmonic) and any addition of waves with these frequencies is periodic at 50 Hz. In music, harmonics are used on string instruments and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Modulation
Frequency modulation (FM) is a signal modulation technique used in electronic communication, originally for transmitting messages with a radio wave. In frequency modulation a carrier wave is varied in its instantaneous frequency in proportion to a property, primarily the instantaneous amplitude, of a message signal, such as an audio signal. The technology is used in telecommunications, radio broadcasting, signal processing, and Run-length limited#FM: .280.2C1.29 RLL, computing. In Analog signal, analog frequency modulation, such as radio broadcasting of voice and music, the instantaneous frequency deviation, i.e. the difference between the frequency of the carrier and its center frequency, has a functional relation to the modulating signal amplitude. Digital data can be encoded and transmitted with a type of frequency modulation known as frequency-shift keying (FSK), in which the instantaneous frequency of the carrier is shifted among a set of frequencies. The frequencies m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplitude Modulation
Amplitude modulation (AM) is a signal modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the instantaneous amplitude of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its Phase (waves), phase, as in phase modulation. AM was the earliest modulation method used for transmitting audio in radio broadcasting. It was developed during the first quarter of the 20th century beginning with Roberto Landell de Moura and Reginald Fessenden's radiotelephone experiments in 1900. This original form of AM is sometimes called double-sideband amplitude modulation (DSBAM), because the standard method produces sidebands on either side of the carrier frequency. Single-sideband modulation uses bandpass filters to eliminate one of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
