Deutsches Institut für Normung
Deutsches Institut für Normung e. V. is the German ISO member body. DIN is a German Registered Association headquartered in Berlin. There are around thirty thousand DIN Standards, covering nearly every field of technology. Founded in 1917 as the Normenausschuß der deutschen Industrie, the NADI was renamed Deutscher Normenausschuß in 1926 to reflect that the organization now dealt with standardization issues in many fields. In 1975 it was renamed again to Deutsches Institut für Normung, or'DIN' and is recognized by the German government as the official national-standards body, representing German interests at the international and European levels; the acronym,'DIN' is incorrectly expanded as Deutsche Industrienorm. This is due to the historic origin of the DIN as "NADI"; the NADI indeed published their standards as DI-Norm. For example, the first published standard was'DI-Norm 1' in 1918. Many people still mistakenly associate DIN with the old DI-Norm naming convention. One of the earliest, the best known, is DIN 476 — the standard that introduced the A-series paper sizes in 1922 — adopted in 1975 as International Standard ISO 216.
Common examples in modern technology include DIN and mini-DIN connectors for electronics, the DIN rail. The designation of a DIN standard shows its origin: DIN # is used for German standards with domestic significance or designed as a first step toward international status. E DIN # is a draft standard and DIN V # is a preliminary standard. DIN EN # is used for the German edition of European standards. DIN ISO # is used for the German edition of ISO standards. DIN EN ISO # is used if the standard has been adopted as a European standard. DIN 476: international paper sizes DIN 1451: typeface used by German railways and on traffic signs DIN 31635: transliteration of the Arabic language DIN 72552: electric terminal numbers in automobiles Austrian Standards Institute Swiss Association for Standardization Die Brücke, an earlier German institute aiming to set standard paper sizes DIN film speed DIN connector DQS - Deutsche Gesellschaft zur Zertifizierung von Managementsystemen, a subsidiary of DIN DGQ - Deutsche Gesellschaft für Qualität, founded DQS in 1985 together with DIN DIN home page DIN home page DIN online dictionary of classes and units of measure DQS Holding GmbH DQS HK
Dolby noise-reduction system
A Dolby noise-reduction system, or Dolby NR, is one of a series of noise reduction systems developed by Dolby Laboratories for use in analog audio tape recording. The first was Dolby A, a professional broadband noise reduction for recording studios in 1965, but the best-known is Dolby B, a sliding band system for the consumer market, which helped make high fidelity practical on cassette tapes which used a noisy tape size and speed, it is common on high fidelity recorders to the present day. Of the noise reduction systems, Dolby A and Dolby SR were developed for professional use. Dolby B, C, S were designed for the consumer market. Aside from Dolby HX, all the Dolby variants work by companding, or compressing the dynamic range of the sound during recording and expanding it during playback; when recording a signal on magnetic tape, there is a low level of "noise" in the background which sounds like hissing. One solution is "low-noise" tape which records more signal, less "noise". Other solutions are to use a wider tape.
Cassette tapes were designed to trade off fidelity for convenience of recording voice by using a narrow tape run at a slow speed of 1 7/8 inches per second in a simple plastic shell when 15 or 7.5 ips was for high fidelity and 3.75 ips was lower fidelity. When Advent designed one of the first cassette tape decks for high fidelity, noise reduction was one way to fix problems with the format, along with chrome and high-bias tapes with extended high frequency response. Within 10 to 20 years, the original reel-to-reel high fidelity tape recorders which did not need noise reduction were replaced by cassette decks for home use; the dominant noise reduction scheme "Dolby B" was accepted because if an inexpensive cassette player lacked the switch, they would just sound brighter which offset the dull sounds of cheap players. The signal to noise ratio is how large the music signal is compared to the low level of the "noise" with no signal; when the music is loud, the low hiss is not noticeable, but when the music is soft or in silence, most of what can be heard is the noise.
If the recording level is adjusted so that the music is always loud it could in theory be turned down and the noise volume would be turned down. The idea is for electronics to automatically increase the recording volume when it is soft, but reduce the volume on playback; some schemes like Dolby B concentrate only on the high frequencies so that the "hiss" sound of noise will be masked when volume is turned down for playback. Dolby noise reduction is a form of dynamic preemphasis employed during recording, plus a form of dynamic deemphasis used during playback, that work in tandem to improve the signal-to-noise ratio. While Dolby A operates across the whole spectrum, the other systems emphasize the audible frequency range where background tape hiss, an artifact of the recording process, similar to white noise, is most noticeable; the Dolby preemphasis boosts the recorded level of the quieter audio signal at these higher frequencies during recording compressing the dynamic range of that portion of the signal, so that quieter sounds above 1 kHz receive a proportionally greater boost.
As the tape is recorded, the relative amplitude of the signal above 1 kHz is used to determine how much pre-emphasis to apply - a low-level signal is boosted by 10 dB or 20 dB. As the signal rises in amplitude and less pre-emphasis is applied until at the "Dolby level", no signal modification is performed; the sound is thus recorded at a higher overall level on the tape relative to the tape's overall noise level, requiring the tape formulation to preserve this specially recorded signal without distortion. On playback, the opposite process is applied, based on the relative signal component above 1 kHz, thus as this portion of the signal decreases in amplitude, the higher frequencies are progressively more attenuated, which filters out the constant background noise on the tape when and where it would be most noticeable. The two processes are intended to cancel each other out as far as the actual recorded program is concerned. Only de-emphasis is applied to noise during playback. After playback de-emphasis is complete, apparent noise in the output signal is reduced, this process should not produce any effect noticeable to the listener.
Playback without noise reduction produces a noticeably brighter sound, however. The calibration of the recording and playback circuitry is therefore critical for faithful reproduction of the original program content, this is offset by poor quality tape, dirty recording/playback heads, or using inappropriate bias levels/frequency for the tape formulation, as well as tape speed, when recording or duplicating; this can manifest itself as muffled-sounding playback, or "breathing" of the noise level as the signal varies. On some high end consumer equipment, Dolby calibration control is included: for recording, a reference tone at Dolby level may be recorded for accurate playback level calibration on another transport. For accurate off-the-tape monitoring during recording on 3-head decks, both processes must be employed at once, circuitry provided to accomplish this is marketed under the rubric "Double Dolby". Dolby A was the company's first noise reduct
In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used, with this or similar meanings, in many scientific and technical disciplines, including physics, acoustical engineering, telecommunications, statistical forecasting. White noise refers to a statistical model for signals and signal sources, rather than to any specific signal. White noise draws its name from white light, although light that appears white does not have a flat power spectral density over the visible band. In discrete time, white noise is a discrete signal whose samples are regarded as a sequence of serially uncorrelated random variables with zero mean and finite variance. Depending on the context, one may require that the samples be independent and have identical probability distribution. In particular, if each sample has a normal distribution with zero mean, the signal is said to be Additive white Gaussian noise; the samples of a white noise signal may be sequential in time, or arranged along one or more spatial dimensions.
In digital image processing, the pixels of a white noise image are arranged in a rectangular grid, are assumed to be independent random variables with uniform probability distribution over some interval. The concept can be defined for signals spread over more complicated domains, such as a sphere or a torus. An infinite-bandwidth white noise signal is a purely theoretical construction; the bandwidth of white noise is limited in practice by the mechanism of noise generation, by the transmission medium and by finite observation capabilities. Thus, random signals are considered "white noise" if they are observed to have a flat spectrum over the range of frequencies that are relevant to the context. For an audio signal, the relevant range is the band of audible sound frequencies; such a signal is heard by the human ear as a hissing sound, resembling the /sh/ sound in "ash". In music and acoustics, the term "white noise" may be used for any signal that has a similar hissing sound; the term white noise is sometimes used in the context of phylogenetically based statistical methods to refer to a lack of phylogenetic pattern in comparative data.
It is sometimes used analogously in nontechnical contexts to mean "random talk without meaningful contents". Any distribution of values is possible. A binary signal which can only take on the values 1 or –1 will be white if the sequence is statistically uncorrelated. Noise having a continuous distribution, such as a normal distribution, can of course be white, it is incorrectly assumed that Gaussian noise refers to white noise, yet neither property implies the other. Gaussianity refers to the probability distribution with respect to the value, in this context the probability of the signal falling within any particular range of amplitudes, while the term'white' refers to the way the signal power is distributed over time or among frequencies. We can therefore find Gaussian white noise, but Poisson, etc. white noises. Thus, the two words "Gaussian" and "white" are both specified in mathematical models of systems. Gaussian white noise is a good approximation of many real-world situations and generates mathematically tractable models.
These models are used so that the term additive white Gaussian noise has a standard abbreviation: AWGN. White noise is the generalized mean-square derivative of the Wiener Brownian motion. A generalization to random elements on infinite dimensional spaces, such as random fields, is the white noise measure. White noise is used in the production of electronic music either directly or as an input for a filter to create other types of noise signal, it is used extensively in audio synthesis to recreate percussive instruments such as cymbals or snare drums which have high noise content in their frequency domain. A simple example of white noise is a nonexistent radio station. White noise is used to obtain the impulse response of an electrical circuit, in particular of amplifiers and other audio equipment, it is not used for testing loudspeakers as its spectrum contains too great an amount of high frequency content. Pink noise, which differs from white noise in that it has equal energy in each octave, is used for testing transducers such as loudspeakers and microphones.
To set up the equalization for a concert or other performance in a venue, a short burst of white or pink noise is sent through the PA system and monitored from various points in the venue so that the engineer can tell if the acoustics of the building boost or cut any frequencies. The engineer can adjust the overall equalization to ensure a balanced mix. White noise is used as the basis of some random number generators. For example, Random.org uses a system of atmospheric antennae to generate random digit patterns from white noise. White noise is a common synthetic noise source used for sound masking by a tinnitus masker. White noise machines and other white noise sources are sold as privacy enhancers and sleep aids and to mask tinnitus. Alternatively, the use of an FM radio tuned to unused frequencies is a simpler and more cost-effective source of white noise. However, white noise generated from a common commercial radio receiver tuned to an unused frequency is vulnerable to being contaminated with spurious signals, such as adjacent radio stations, harmonics f
The Deutsche Bundespost was a German state-run postal service and telecommunications business founded in 1947. It was the second largest federal employer during its time. After staff reductions in the 1980s, the staff was reduced to 543,200 employees in 1985; the corporation was dissolved in 1995 under the first and second postal reforms that took place in the German Post Office. Following the reforms, the former Deutsche Bundespost was broken into three publicly traded corporations: Deutsche Post AG, Deutsche Telekom, Deutsche Postbank AG, it was created in 1947 in the Trizone as a successor to the Reichspost. Between 1947 and 1950 the enterprise was called Deutsche Post; until 1989 the Deutsche Bundespost was a state-owned operation. The Bundespost was developed according to a three-tier principle common in public administration in the Federal Republic of Germany; the upper stage consisted of the federal ministry for the post telecommunication system. The middle stage consisted of regional directorates and the state post office management under western Allied authority in West Berlin as of 1949/1955).
The post office technical central office, telecommunication engineering central office, postal administration social office, post offices) were on an equal level with the directorates. The lower stage consisted of post office branches, postal giro savings bank offices and telecommunications office branches; the legal basis for the administrative activity of the Bundespost was the postal administration act. A central goal of public administrative policy after 1924 was financial self-sufficiency. Political goals, however superseded this goal. According to the PostVwG, the federal postal system was to be administered "according to the principles of the policy of the FRG, in particular trade, economic and social policies" and "the interests of the German national economy." The Deutsche Bundespost was the largest employer in the Federal Republic. In 1985 it employed 543,200 people. In the first post office reform, the Bundespost was divided into three divisions: Deutsche Bundespost Postdienst - postal service Deutsche Bundespost Telekom - communications service Deutsche Bundespost Postbank - postal bankThe central authorities remained as described above.
The divisions were privatized in the second post office reform, resulting in: Deutsche Post AG from the postal service Deutsche Telekom AG from the communications service Deutsche Postbank AG from the postal bankThe federal ministry for post office and telecommunications retained oversight responsibility for postal services and telecommunications. After the dissolution of that ministry on 1 January 1998, those tasks were taken over by a new federal network regulatory agency under the federal ministry for economics and technology. Other functions were taken over by the federal ministry of finance; some telecommunications functions were turned over to the federal ministry of the interior. For certain official and legal purposes, a "federal institution for post and telecommunication" was created. Postage stamps and postal history of Germany Deutsche Bundespost Berlin Deutsche Post of the GDR
FM broadcasting is a method of radio broadcasting using frequency modulation technology. Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high-fidelity sound over broadcast radio. FM broadcasting is capable of better sound quality than AM broadcasting, the chief competing radio broadcasting technology, so it is used for most music broadcasts. Theoretically wideband AM can offer good sound quality, provided the reception conditions are ideal. FM radio stations use the VHF frequencies; the term "FM band" describes the frequency band in a given country, dedicated to FM broadcasting. Throughout the world, the FM broadcast band falls within the VHF part of the radio spectrum. 87.5 to 108.0 MHz is used, or some portion thereof, with few exceptions: In the former Soviet republics, some former Eastern Bloc countries, the older 65.8–74 MHz band is used. Assigned frequencies are at intervals of 30 kHz; this band, sometimes referred to as the OIRT band, is being phased out in many countries.
In those countries the 87.5–108.0 MHz band is referred to as the CCIR band. In Japan, the band 76–95 MHz is used; the frequency of an FM broadcast station is an exact multiple of 100 kHz. In most of South Korea, the Americas, the Philippines and the Caribbean, only odd multiples are used. In some parts of Europe and Africa, only multiples are used. In the UK odd or are used. In Italy, multiples of 50 kHz are used. In most countries the maximum permitted frequency error is specified, the unmodulated carrier should be within 2000 Hz of the assigned frequency. There are other unusual and obsolete FM broadcasting standards in some countries, including 1, 10, 30, 74, 500, 300 kHz. However, to minimise inter-channel interference, stations operating from the same or geographically close transmitter sites tend to keep to at least a 500 kHz frequency separation when closer frequency spacing is technically permitted, with closer tunings reserved for more distantly spaced transmitters, as interfering signals are more attenuated and so have less effect on neighboring frequencies.
Frequency modulation or FM is a form of modulation which conveys information by varying the frequency of a carrier wave. With FM, frequency deviation from the assigned carrier frequency at any instant is directly proportional to the amplitude of the input signal, determining the instantaneous frequency of the transmitted signal; because transmitted FM signals use more bandwidth than AM signals, this form of modulation is used with the higher frequencies used by TV, the FM broadcast band, land mobile radio systems. The maximum frequency deviation of the carrier is specified and regulated by the licensing authorities in each country. For a stereo broadcast, the maximum permitted carrier deviation is invariably ±75 kHz, although a little higher is permitted in the United States when SCA systems are used. For a monophonic broadcast, again the most common permitted. However, some countries specify a lower value for monophonic broadcasts, such as ±50 kHz. Random noise has a triangular spectral distribution in an FM system, with the effect that noise occurs predominantly at the highest audio frequencies within the baseband.
This can be offset, to a limited extent, by boosting the high frequencies before transmission and reducing them by a corresponding amount in the receiver. Reducing the high audio frequencies in the receiver reduces the high-frequency noise; these processes of boosting and reducing certain frequencies are known as pre-emphasis and de-emphasis, respectively. The amount of pre-emphasis and de-emphasis used is defined by the time constant of a simple RC filter circuit. In most of the world a 50 µs time constant is used. In the Americas and South Korea, 75 µs is used; this applies to both stereo transmissions. For stereo, pre-emphasis is applied to the left and right channels before multiplexing; the use of pre-emphasis becomes a problem because of the fact that many forms of contemporary music contain more high-frequency energy than the musical styles which prevailed at the birth of FM broadcasting. Pre-emphasizing these high frequency sounds would cause excessive deviation of the FM carrier. Modulation control devices are used to prevent this.
Systems more modern than FM broadcasting tend to use either programme-dependent variable pre-emphasis. Long before FM stereo transmission was considered, FM multiplexing of other types of audio level information was experimented with. Edwin Armstrong who invented FM was the first to experiment with multiplexing, at his experimental 41 MHz station W2XDG located on the 85th floor of the Empire State Building in New York City; these FM multiplex transmissions started in November 1934 and consisted of the main channel audio program and three subcarriers: a fax program, a synchronizing signal for the fax program and a telegraph “order” channel. These original FM multiplex subcarriers were amplitude modulated. Two musical programs, consisting of both the Red and Blue Network program feeds of the NBC Radio Network, were transmitted using the same system of subcarrier modulation as part of a studio-to-transmitter link system. In April 1935, the AM subcarriers were replaced with much improved results.
The first FM subcarrier transmissions emanating from Major Armstrong's experimental station KE2XCC at Alpine, New Jersey occurred in 1948. These transmissions consisted of two-cha
International Telecommunication Union
The International Telecommunication Union the International Telegraph Union, is a specialized agency of the United Nations, responsible for issues that concern information and communication technologies. It is the oldest among all the 15 specialised agencies of UN; the ITU coordinates the shared global use of the radio spectrum, promotes international cooperation in assigning satellite orbits, works to improve telecommunication infrastructure in the developing world, assists in the development and coordination of worldwide technical standards. The ITU is active in areas including broadband Internet, latest-generation wireless technologies and maritime navigation, radio astronomy, satellite-based meteorology, convergence in fixed-mobile phone, Internet access, voice, TV broadcasting, next-generation networks; the agency organizes worldwide and regional exhibitions and forums, such as ITU Telecom World, bringing together representatives of government and the telecommunications and ICT industry to exchange ideas and technology.
ITU, based in Geneva, Switzerland, is a member of the United Nations Development Group, has 12 regional and area offices in the world. ITU has been an intergovernmental public–private partnership organization since its inception, its membership includes 193 Member States and around 800 public and private sector companies, academic institutions as well as international and regional telecommunication entities, known as Sector Members and Associates, which undertake most of the work of each Sector. ITU was formed in Paris, at the International Telegraph Convention; the International Radiotelegraph Union was unofficially established at first International Radiotelegraph Convention in 1906. Both were merged into the International Telecommunication Union in 1932. ITU became a United Nations specialized agency in 1947; the ITU comprises three sectors, each managing a different aspect of the matters handled by the Union, as well as ITU Telecom. The sectors were created during the restructuring of ITU at its 1992 Plenipotentiary Conference.
Radio communication Established in 1927 as the International Radio Consultative Committee or CCIR, this sector manages the international radio-frequency spectrum and satellite orbit resources. In 1992, the CCIR became the ITU-R. Standardisation Standardisation was the original purpose of ITU since its inception. Established in 1956 as the International Telephone and Telegraph Consultative Committee or CCITT, this sector standardizes global telecommunications. In 1993, the CCITT became the ITU-T. Development Established in 1992, this sector helps spread equitable and affordable access to information and communication technologies. ITU Telecom ITU Telecom organizes major events for the world's ICT community. A permanent General Secretariat, headed by the Secretary General, manages the day-to-day work of the Union and its sectors; the basic texts of the ITU are adopted by the ITU Plenipotentiary Conference. The founding document of the ITU was the 1865 International Telegraph Convention, which has since been amended several times and is now entitled the "Constitution and Convention of the International Telecommunication Union".
In addition to the Constitution and Convention, the consolidated basic texts include the Optional Protocol on the settlement of disputes, the Decisions and Recommendations in force, as well as the General Rules of Conferences and Meetings of the Union. The ITU is headed by a Secretary-General, a Deputy Secretary General and the three directors of the Bureaux, who are elected to a four-year terms by the member states at the ITU Plenipotentiary Conference. On 23 October 2014 Houlin Zhao was elected 19th Secretary-General of the ITU at the Plenipotentiary Conference in Busan, Republic of Korea, his four-year mandate started on 1 January 2015, he was formally inaugurated on 15 January 2015. Houlin Zhao was reelected at the 2018 Plenipotentiary Conference in Dubai. Membership of ITU is open to only Member States of the United Nations, which may join the Union as Member States, as well as to private organizations like carriers, equipment manufacturers, funding bodies and development organizations and international and regional telecommunication organizations, which may join ITU as non-voting Sector Members.
There are 193 Member States of the ITU, including all UN member states except the Republic of Palau, plus the Vatican City. The most recent member state to join the ITU is South Sudan, which became a member on 14 July 2011; the Republic of China was blocked from membership by the People's Republic of China, but received a country code, being listed as "Taiwan, China". Palestine was admitted as an observer in 2010. Six Regional Offices and seven Area Offices guarantee a regional presence of ITU: Regional Office for CSI Africa Regional Office in Addis Ababa, with Area Offices in Dakar and Yaoundé Arab States Regional Office in Cairo Asia-Pacific Regional Office in Bangkok, with Area Office in Jakarta America Regional Office in Brasilia, with Area Offices in Bridgetown and Tegucigalpa; the sixth is a Coordination office for Europe Region Europe at ITU Headquarters. Other Regional organizations, connected to ITU, are: Asia-Pacific Telecommunity Arab Spectrum Management Group African Telecommunications Union European Conference of Posta