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Cleanroom

A cleanroom or clean room is an engineered space that maintains a very low concentration of airborne particulates. It is well isolated, well controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientific research and in industrial production for all nanoscale processes, such as semiconductor manufacturing. A cleanroom is designed to keep everything from dust to airborne organisms or vaporised particles away from it, and so from whatever material is being handled inside it.

A cleanroom can also prevent the escape of materials. This is often the primary aim in hazardous biology, nuclear work, pharmaceutics and virology.

Cleanrooms typically come with a cleanliness level quantified by the number of particles per cubic meter at a predetermined molecule measure. The ambient outdoor air in a typical urban area contains 35,000,000 particles for each cubic meter in the size range 0.5 μm and bigger, equivalent to an ISO 9 certified cleanroom. By comparison, an ISO 14644-1 level 1 certified cleanroom permits no particles in that size range, and just 12 particles for each cubic meter of 0.3 μm and smaller. Semiconductor facilities often get by with level 7 or 5, while level 1 facilities are exceedingly rare.

History
The modern cleanroom was invented by American physicist Willis Whitfield. As an employee of the Sandia National Laboratories, Whitfield created the initial plans for the cleanroom in 1960. Prior to Whitfield's invention, earlier cleanrooms often had problems with particles and unpredictable airflows. Whitfield designed his cleanroom with a constant, highly filtered airflow to flush out impurities. Within a few years of its invention in the 1960s, Whitfield's modern cleanroom had generated more than US$50 billion in sales worldwide (approximately $ billion today).

The majority of the integrated circuit manufacturing facilities in Silicon Valley were made by three companies: MicroAire, PureAire, and Key Plastics. These competitors made laminar flow units, glove boxes, cleanrooms and air showers, along with the chemical tanks and benches used in the "wet process" building of integrated circuits. These three companies were the pioneers of the use of Teflon for airguns, chemical pumps, scrubbers, water guns, and other devices needed for the production of integrated circuits. William (Bill) C. McElroy Jr. worked as an engineering manager, drafting room supervisor, QA/QC, and designer for all three companies, and his designs added 45 original patents to the technology of the time. McElroy also wrote a four-page article for MicroContamination Journal, wet processing training manuals, and equipment manuals for wet processing and cleanrooms.

Overview
A cleanroom is a necessity in the manufacturing of semiconductors and rechargeable batteries, the life sciences, and any other field that is highly sensitive to environmental contamination.

Cleanrooms can range from the very small to the very large. On the one hand, a single-user laboratory can be built to cleanroom standards within several square meters, and on the other, entire manufacturing facilities can be contained within a cleanroom with factory floors covering thousands of square meters. Between the large and the small, there are also modular cleanrooms. They have been argued to lower costs of scaling the technology, and to be less susceptible to catastrophic failure.

With such a wide area of application, not every cleanroom is the same. For example, the rooms utilized in semiconductor manufacturing need not be sterile (i.e., free of uncontrolled microbes), while the ones used in biotechnology usually must be. Vice versa, operating rooms need not be absolutely pure of nanoscale inorganic salts, such as rust, while nanotechnology absolutely requires it. What then is common to all cleanrooms is strict control of airborne particulates, possibly with secondary decontamination of air, surfaces, workers entering the room, implements, chemicals, and machinery.

Sometimes particulates exiting the compartment are also of concern, such as in research into dangerous viruses, or where radioactive materials are being handled.

Basic construction
First, outside air entering a cleanroom is filtered and cooled by several outdoor air handlers using progressively finer filters to exclude dust.

Within, air is constantly recirculated through fan units containing high-efficiency particulate absorbing filters (HEPA), and/or ultra-low particulate air (ULPA) filters to remove internally generated contaminants. Special lighting fixtures, walls, equipment and other materials are used to minimize the generation of airborne particles. Plastic sheets can be used to restrict air turbulence if the cleanroom design is of the laminar airflow type.

Air temperature and humidity levels inside a cleanroom are tightly controlled, because they affect the efficiency and means of air filtration. If a particular room requires low enough humidity to make static electricity a concern, it too will be controlled by, e.g., introducing controlled amounts of charged ions into the air using a corona discharge. Static discharge is of particular concern in the electronics industry, where it can instantly destroy components and circuitry.

Equipment inside any cleanroom is designed to generate minimal air contamination. The selection of material for the construction of a cleanroom should not generate any particulates; hence, monolithic epoxy or polyurethane floor coating is preferred. Buffed stainless steel or powder-coated mild steel sandwich partition panels and ceiling panel are used instead of iron alloys prone to rusting and then flaking. Corners like the wall to wall, wall to floor, wall to ceiling are avoided by providing coved surface, and all joints need to be sealed with epoxy sealant to avoid any deposition or generation of particles at the joints, by vibration and friction. Many cleanrooms have a "tunnel" design in which there are spaces called "service chases" that serve as air plenums carrying the air from the bottom of the room to the top so that it can be recirculated and filtered at the top of the cleanroom.

Airflow principles
Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or turbulent airflow principles. Laminar, or unidirectional, airflow systems direct filtered air downward or in horizontal direction in a constant stream towards filters located on walls near the cleanroom floor or through raised perforated floor panels to be recirculated. Laminar airflow systems are typically employed across 80% of a cleanroom ceiling to maintain constant air processing. Stainless steel or other non shedding materials are used to construct laminar airflow filters and hoods to prevent excess particles entering the air. Turbulent, or non-unidirectional, airflow uses both laminar airflow hoods and nonspecific velocity filters to keep air in a cleanroom in constant motion, although not all in the same direction. The rough air seeks to trap particles that may be in the air and drive them towards the floor, where they enter filters and leave the cleanroom environment. US FDA and EU have laid down stringent guidelines and limits to ensure freedom from microbial contamination in pharmaceutical products. Plenums between air handlers and fan filter units, along with sticky mats, may also be used.

In addition to air filters, cleanrooms can also use ultraviolet light to disinfect the air. UV devices can be fitted into ceiling light fixtures and irradiate air, killing potentially infectious particulates, including 99.99 percent of airborne microbial and fungal contaminants. UV light has previously been used to clean surface contaminants in sterile environments such as hospital operating rooms. Their use in other cleanrooms may increase as equipment becomes more affordable. Potential advantages of UV-based decontamination includes a reduced reliance on chemical disinfectants and the extension of HVAC filter life.

Cleanrooms of different kinds
Some cleanrooms are kept at a positive pressure so if any leaks occur, air leaks out of the chamber instead of unfiltered air coming in. This is most typically the case in semiconductor manufacturing, where even minute amounts of particulates leaking in could contaminate the whole process, while anything leaking out. The opposite is done, e.g., in the case of high-level bio-laboratories that handle dangerous bacteria or viruses; those are always held at negative pressure, with the exhaust being passed through high-efficiency filters, and further sterilizing procedures. Both are still cleanrooms because the particulate level inside is maintained within very low limits.

Some cleanroom HVAC systems control the humidity to such low levels that extra equipment like air ionizers are required to prevent electrostatic discharge problems. This is a particular concern within the semiconductor business, because static discharge can easily damage modern circuit designs. On the other hand, active ions in the air can harm exposed components as well. Because of this, most workers in high electronics and semiconductor facilities have to wear conductive boots while working. Low-level cleanrooms may only require special shoes, with completely smooth soles that do not track in dust or dirt. However, for safety reasons, shoe soles must not create slipping hazards. Access to a cleanroom is usually restricted to those wearing a cleanroom suit, including the necessary machinery.

In cleanrooms in which the standards of air contamination are less rigorous, the entrance to the cleanroom may not have an air shower. An anteroom (known as a "gray room") is used to put on cleanroom clothing. This practice is common in many nuclear power plants, which operate as low-grade inverse pressure cleanrooms, as a whole.

Recirculating vs. one pass cleanrooms

Recirculating cleanrooms return air to the negative pressure plenum via low wall air returns. The air then is pulled by HEPA fan filter units back into the cleanroom. The air is constantly recirculating and by continuously passing through HEPA filtration removing particles from the air each time. Another advantage of this design is that air conditioning can be incorporated.

One pass cleanrooms draw air from outside and pass it through HEPA fan filter units into the cleanroom. The air then leaves through exhaust grills. The advantage of this approach is the lower cost. The disadvantages are comparatively shorter HEPA fan filter life, worse particle counts than a recirculating cleanroom, and that it cannot accommodate air conditioning.

Operating procedure
In order to minimize the carrying of particulate by a person moving into the cleanroom, staff enter and leave through airlocks (sometimes including an air shower stage) and wear protective clothing such as hoods, face masks, gloves, boots, and coveralls.

Common materials such as paper, pencils, and fabrics made from natural fibers are often excluded because they shed particulates in use.

Particle levels are usually tested using a particle counter and microorganisms detected and counted through. Polymer tools used in cleanrooms must be carefully determined to be chemically compatible with cleanroom processing fluids as well as ensured to generate a low level of particle generation.

When cleaning, only special mops and buckets are used. Cleaning chemicals used tend to involve sticky elements to trap dust, and may need a second step with light molecular weight solvents to clear. Cleanroom furniture is designed to produce a minimum of particles and is easy to clean.

A cleanroom is as much a process and a meticulous culture to maintain, as it is a space as such.

Personnel contamination of cleanrooms
The greatest threat to cleanroom contamination comes from the users themselves. In the healthcare and pharmaceutical sectors, control of microorganisms is important, especially microorganisms likely to be deposited into the air stream from skin shedding. Studying cleanroom microflora is of importance for microbiologists and quality control personnel to assess changes in trends. Shifts in the types of microflora may indicate deviations from the "norm" such as resistant strains or problems with cleaning practices.

In assessing cleanroom microorganisms, the typical flora are primarily those associated with human skin (Gram-positive cocci), although microorganisms from other sources such as the environment (Gram-positive rods) and water (Gram-negative rods) are also detected, although in lower number. Common bacterial genera include Micrococcus, Staphylococcus, Corynebacterium, and Bacillus, and fungal genera include Aspergillus and Penicillium.

Cleanroom classification and standardization
Cleanrooms are classified according to the number and size of particles permitted per volume of air. Large numbers like "class 100" or "class 1000" refer to FED-STD-209E, and denote the number of particles of size 0.5 μm or larger permitted per cubic foot of air. The standard also allows interpolation; for example SNOLAB is maintained as a class 2000 cleanroom.

A discrete, light-scattering airborne particle counter is used to determine the concentration of airborne particles, equal to and larger than the specified sizes, at designated sampling locations.

Small numbers refer to ISO 14644-1 standards, which specify the decimal logarithm of the number of particles 0.1 μm or larger permitted per m3 of air. So, for example, an ISO class 5 cleanroom has at most 105 particles/m3.

Both FS 209E and ISO 14644-1 assume log-log relationships between particle size and particle concentration. For that reason, zero particle concentration does not exist. Some classes do not require testing some particle sizes, because the concentration is too low or too high to be practical to test for, but such blanks should not be read as zero.

Because 1 m3 is about 35 ft3, the two standards are mostly equivalent when measuring 0.5 μm particles, although the testing standards differ. Ordinary room air is around class 1,000,000 or ISO 9.

ISO 14644-1 and ISO 14698
ISO 14644-1 and ISO 14698 are non-governmental standards developed by the International Organization for Standardization (ISO). The former applies to cleanrooms in general (see table below), the latter to cleanrooms where biocontamination may be an issue. Since the strictest standards have been achieved only for space applications, it is sometimes difficult to know whether they were achieved in vacuum or standard conditions.

ISO 14644-1 defines the maximum concentration of particles per class and per particle size with the following formula

$$\text{C}_\text{N} = 10^{\text{N}} \left(\frac{0.1}{\text{D}}\right)^{2.08}$$

Where $$\text{C}_\text{N}$$ is the maximum concentration of particles in a volume of 1m$$^3$$ of airborne particles that are equal to, or larger, than the considered particle size which is rounded to the nearest whole number, using no more than three significant figures, $$\text{N}$$ is the ISO class number, $$\text{D}$$ is the size of the particle in $$\mu$$m and 0.1 is a constant expressed in $$\mu$$m. The result for standard particle sizes is expressed in the following table.

US FED STD 209E
US FED-STD-209E was a United States federal standard. It was officially cancelled by the General Services Administration on November 29, 2001, but is still widely used.

Current regulating bodies include ISO, USP 800, US FED STD 209E (previous standard, still used).

 * Drug Quality and Security Act (DQSA) created in Nov. 2013 in response to drug compounding deaths and serious adverse events.
 * The Federal Food, Drug, and Cosmetic Act (FD&C Act) created specific guidelines and policies for human compounding.
 * 503A addresses compounding by state or federally licensed facility by licensed personnel (pharmacist/ physicians)
 * 503B pertaining to outsourcing facilities need direct supervision from a licensed pharmacist and do not need to be a licensed pharmacy. Facility is licensed through the Food and Drug Administration (FDA)

EU GMP classification
EU GMP guidelines are more stringent than others, requiring cleanrooms to meet particle counts at operation (during manufacturing process) and at rest (when manufacturing process is not carried out, but room AHU is on).

BS 5295
BS 5295 is a British Standard.

BS 5295 Class 1 also requires that the greatest particle present in any sample can not exceed 5 μm. BS 5295 has been superseded, withdrawn since the year 2007 and replaced with "BS EN ISO 14644-6:2007".

USP Standards
USP 800 is a United States standard developed by the United States Pharmacopeial Convention (USP) with an effective date of December 1, 2019.

Ramifications and further applications
In hospitals, theatres are similar to cleanrooms for surgical patients' operations with incisions to prevent any infections for the patient.

In another case, severely immunocompromised patients sometimes have to be held in prolonged isolation from their surroundings, for fear of infection. At the extreme, this necessitates a cleanroom environment. The same is the case for patients carrying airborne infectious diseases, only they are handled at negative, not positive pressure.

In exobiology when we seek out contact with other planets, there is a biological hazard both ways: we must not contaminate any sample return missions from other stellar bodies with terrestrial microbes, and we must not contaminate possible other ecosystems existing in other planets. Thus, even by international law, any probes we send to outer space must be sterile, and so to be handled in cleanroom conditions.

Since larger cleanrooms are very sensitive controlled environments upon which multibillion-dollar industries depend, sometimes they are even fitted with numerous seismic base isolation systems to prevent costly equipment malfunction.

title: Cleanroom


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Caveat emptor

Caveat emptor (from caveat, "may he/she beware", a subjunctive form of cavēre, "to beware" + ēmptor, "buyer") is Latin for "Let the buyer beware". It has become a proverb in English. Generally, caveat emptor is the contract law principle that controls the sale of real property after the date of closing, but may also apply to sales of other goods. The phrase caveat emptor and its use as a disclaimer of warranties arises from the fact that buyers typically have less information than the seller about the good or service they are purchasing. This quality of the situation is known as 'information asymmetry'. Defects in the good or service may be hidden from the buyer, and only known to the seller.

It is a short form of Caveat emptor, quia ignorare non debuit quod jus alienum emit ("Let a purchaser beware, for he ought not to be ignorant of the nature of the property which he is buying from another party.") I.e. the buyer should assure himself that the product is good and that the seller had the right to sell it, as opposed to receiving stolen property.

A common way that information asymmetry between seller and buyer has been addressed is through a legally binding warranty, such as a guarantee of satisfaction.

Explanation
Under the principle of caveat emptor, the buyer could not recover damages from the seller for defects on the property that rendered the property unfit for ordinary purposes. The only exception was if the seller actively concealed latent defects or otherwise made material misrepresentations amounting to fraud.

Before statutory law, the buyer had no express warranty ensuring the quality of goods. In the UK, common law requires that goods must be "fit for the particular purpose" and of "merchantable quality", per Section 15 of the Sale of Goods Act but this implied warranty can be difficult to enforce and may not apply to all products. Hence, buyers are still advised to be cautious.

Real estate
The modern trend in the U.S. is that the implied warranty of fitness for a particular purpose applies in the real-estate context to only the sale of new residential housing by a builder-seller and that the caveat emptor rule applies to all other real-estate sale situations (e.g. homeowner to buyer). Other jurisdictions have provisions similar to this.

Chattel property
Under Article 2 of the Uniform Commercial Code, the sale of new goods is governed by the "perfect-tender" rule unless the parties to the sale expressly agree in advance to terms equivalent to caveat emptor (such as describing the goods as sold "as is" and/or "with all faults") or other limitations such as the below-discussed limitations on remedies. The perfect-tender rule states that if a buyer who inspects new goods with reasonable promptness discovers them to be "nonconforming" (failing to meet the description provided or any other standards reasonably expectable by a buyer in his/her situation) and does not use the goods or take other actions constituting acceptance of them, the buyer may promptly return or refuse to accept ("reject") them and demand that the defect be remedied ("cured"). When goods fitting the same description and expectations are available for sale (e.g., when the vendor has other instances of the same mass-produced merchandise in stock inventory), either the vendor or the buyer may insist on an "even exchange" for other, "conforming" instances of the product. When conforming goods are not available in stock but are available for the dealer to purchase (usually on the open or "spot" market), the buyer may require that the seller obtain the goods elsewhere, even at a higher price, with the seller having to incur a loss equivalent to the price difference. If the vendor still does not or cannot provide the goods and the dispute proceeds to litigation (as opposed to renegotiation or settlement), then as in all cases of vendor breaches of contract, the buyer may recover only the damages that s/he would have suffered had s/he taken all feasible steps to minimize ("mitigate") his/her damages suffered.

As a default rule, the perfect-tender rule may be "contracted around" in ways that specify or limit a buyer's remedies (and that accordingly reduce the market price that rational buyers are willing to pay for the goods). In many cases, the vendor will not provide a refund but will provide store credit. In the cases of software, movies, and other copyrighted material, many vendors will offer only a direct exchange for another copy of the same title, with the effect that the initial transfer or license of intellectual-property rights is preserved. Most stores require proof of purchase and impose time limits on exchanges or refunds. Some larger chain stores, such as F.Y.E., Staples, Target, or Walmart, will, however, do exchanges or refunds at any time, with or without proof of purchase, although they usually require a form of picture identification and place per-transaction and/or per-person quantity or dollar limitations on such returns.

United Kingdom
In the UK, consumer law has moved away from the caveat emptor model, with laws passed that have enhanced consumer rights and allow greater leeway to return goods that do not meet legal standards of acceptance. Consumer purchases are regulated by the Consumer Rights Act 2015, whilst business-to-business purchases are regulated by the Sale of Goods Act 1979.

In the UK, consumers have the right to a full refund for faulty goods. However, traditionally, many retailers allow customers to return goods within a specified period (typically two weeks to two months) for a full refund or an exchange, even if there is no fault with the product. Exceptions may apply for goods sold as damaged or to clear.

Goods bought through "distance selling," for example online or by phone, also have a statutory "cooling off" period of fourteen calendar days during which the purchase contract can be cancelled and treated as if not done.

Although no longer applied in consumer law, the principle of caveat emptor is generally held to apply to transactions between businesses unless it can be shown that the seller had a clear information advantage over the buyer that could not have been removed by carrying out reasonable due diligence.

Caveat venditor
Caveat venditor is Latin for "let the seller beware."

In the landmark case of MacPherson v. Buick Motor Co. (1916), New York Court Appeals Judge Benjamin N. Cardozo established that privity of duty is no longer required in regard to a lawsuit for product liability against the seller. This case is widely regarded as the origin of caveat venditor as it pertains to modern tort law in US.

Caveat lector
Caveat lector is a Latin phrase meaning "let the reader beware". It means that when reading something, the reader should take careful note of the contents, and undertake due diligence on whether the contents are accurate, relevant, reliable and so forth.

Caveat auditor
Another variant is Caveat Auditor, or "let the listener beware", where caution is urged regarding all messages, in particular spoken messages, such as a radio advertisement.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Caveat emptor


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Marsaxlokk

Marsaxlokk is a small, traditional fishing village in the South Eastern Region of Malta. It has a harbour, and is a tourist attraction known for its views, fishing and history. As of March 2014, the village had a population of 3,534. The village is also known for the Marsaxlokk Market, which is mainly a large fish market which takes place along the seafront on Sundays, and a tourist market during all other days of the week. Inhabited and well-known since antiquity, Marsaxlokk was used as a port by Phoenicians, Carthaginians and also has the remains of a Roman-era harbour. Originally a part of the city of Żejtun, the fishing village became a separate parish in the late nineteenth century.

Traditional luzzi and other larger and more modern vessels line the sheltered inner harbour. The village is also popular among locals and tourists alike for its walks around the coast and harbour, its restaurants, as well as for its swimming zones. Marsaxlokk Bay also includes a container freeport towards Birżebbuġa, a power station complex towards Delimara, and a small ship-repair facility for fishermen.

Marsaxlokk is sometimes referred to as Portus Herculis, due to the association of Marsaxlokk Bay with the Roman and Punic remains at Tas-Silġ.

Etymology
The name Marsaxlokk comes from the Arabic word marsa, which means port and xlokk, which is the Maltese word for south-east. The word is related to the name for the dry sirocco wind that blows from the Sahara, comparable to the equivalent Catalan word, xaloc. The inhabitants of the village are called the Xlukkajri and are, traditionally, fishermen by trade.

Topography
Situated in the south-east end of the main island of Malta, Marsaxlokk bay is fed by a valley that drains the Marnisi and Ħal Ġinwi areas. The Marsaxlokk floodplain is one of the smaller ones on Malta. Today, a small marsh survives at the head of the bay, named Tal-Magħluq. This may indicate that the bay may have been larger in the past and gradually silted up since antiquity. Although there are no sources from the medieval and early modern period to prove the existence of marshes in the area, a marshy environment survives at the head of the fishing harbour.

Sediment deposition over recent century has silted the bay, making it significantly more shallow than in antiquity. Researchers hypothesize that vessels of all sizes could once have sought shelter here. A sandy beach may have provided a landing place for small boats. A freshwater supply exists in the valley that lies between two of the three hills dominating the bay - namely to the north-east, north and north-west. Access to plains around Żejtun would have been easy via this same valley, with a meandering road linking the bay to the Żejtun Roman Villa. While the bay could only have been used as a temporary anchorage without human intervention, a simple sea wall may have enabled the harbour to be used as an all-weather anchorage. In antiquity, its main function would have been to serve the agricultural sites in the surrounding areas. It may also have enjoyed links with the Tas-Silġ sanctuary overlooking the bay.

History

To the north-east of the village, on the rounded hilltop of Tas-Silġ, there is a multi-period sanctuary site covering all eras from the Neolithic to the fourth century AD. The Tas-Silġ site includes megalithic remains, scattered edifices belonging to three distinct temples. Cicero describes the temple of Juno in Malta in his In Verrem. The temple, long associated with the remains at Tas-Silġ, contained "a large number of ornaments among which was a carefully and supremely crafted ancient ivory statue of Victory." The presence of such ornaments is a clear indication of the importance of this temple not just locally but also on a Mediterranean scale. Recent studies of the ceramics from Tas-Silġ led to conclusions that the sanctuary was used as a centre of exchange for both local and imported goods. The remains atop the hill also include a more recent Byzantine basilica and monastery.

Little is known about the area during the Middle Ages, with all the casalia of the south-eastern side of the island being exposed to frequent raids and attacks by Saracen pirates and, later, raiders from the Barbary coast. Modern historical studies and topology confirm that the area between Żejtun and Marsaxlokk was covered in vegetation and pasture land. In the later Middle Ages, Marsaxlokk was included in medieval portolani. At least three of these medieval sailing instructions, dating as far back as the 13th century mention, Marsaxlokk (as marza sinocho, Marsa silocco and marza per sirocho). The Rizo portolan of 1490 gives sailing distances from Marsaxlokk to a variety of other ports in the Mediterranean including Tunis, Cephalonia and Tripoli in Libya. This reflects the port's connectivity with other parts of the medieval Mediterranean.

The invading Ottoman navy anchored at Marsaxlokk during the Great Siege of 1565, before they completed the attack on Fort Saint Elmo. The whole harbour area was systematically fortified over successive centuries, with towers, batteries and fortresses ringing Marsaxlokk bay. This chain of fortifications was intended to protect the vulnerable harbour, and included Vendôme Tower, Fort Delimara, Delimara Tower, Ta' Bettina Tower, and Fort Tas-Silġ on Delimara point, on the north arm of Marsaxlokk Bay, Fort San Lucian on Kbira point in the middle of the bay, and the Pinto and Ferretti batteries on the shores of the bay towards Birżebbuġa. The most prominent fortification of this chain, Fort San Lucian was built by 1611 and may have prevented a landing in the bay by Ottoman forces in 1614. Napoleon's navy entered Marsaxlokk, and landed an army on the coast during the French invasion of 1798. During the Maltese uprising - British, Neapolitan and Portuguese forces operated from here. Horatio Nelson and his lover Emma Hamilton also stayed here from April to June 1800, visiting parts of the island.

Most of the fishermen who worked out of Marsaxlokk bay hailed from Żejtun, commuting back and forth from the shore. Around 1846, the first houses began to be built in Marsaxlokk, as fishermen from Żejtun settled there permanently. At the end of the nineteenth century, a church was built to minister to the spiritual needs of the fishermen and their families. Eventually, the fishing village of Marsaxlokk was separated from Żejtun and became a distinct parish in January 1897. The construction of the parish church started in 1890. It was built as a fulfillment of a promise made by Marquess Rosalia Apap Viani Testaferrata after she was saved from a violent storm at sea. The church was originally built in a rectangular form with the designs attributed to Dun Ġużepp Diacono. Marsaxlokk became an independent parish in 1897. The feast of our lady is held on the last Sunday of July. It includes a procession with the statue and a firework display.

In the 1930s, Marsaxlokk bay was used as a staging post by four-engined Short C-Class flying boats of Britain's Imperial Airways as they pioneered long-distance air travel to across the British Empire. During the Second World War, Marsaxlokk Bay was the base for the Fleet Air Arm with a base at Kalafrana. In 1989, the famous summit meeting between Soviet and US leaders Mikhail Gorbachev and George H.W. Bush was held on board a ship anchored in the bay. Today, the village is framed by the fuel tanks and chimneys of the 537.8-megawatt Delimara Power Station, and the huge cranes of the Malta Freeport Container Terminal.

In recent years, Marsaxlokk has also developed as a modern seaside resort. The village includes a natural park at Xrobb l-Għaġin.

Cultural tradition
Marsaxlokk is also famous for the national boats which are the luzzu and the kajjik. They serve the fisherman on fishing near the shore and for fishing away from the shore they use another type of boat. Tourists also can take boat trips from Marsaxlokk to Delimara and Birzebbuġa.

Most of Malta's fish supplies are caught by fishermen coming from this port as about 70% of the Maltese fishing fleet is based there. Swordfish, tuna, and 'lampuki' are caught in abundance between spring and late autumn. On weekdays, the catch is taken to the fish-market in Marsa, but on Sundays, fresh fish is sold by fishermen directly on the quay.

Sports
Marsaxlokk F.C., formed in 1949, is the village's main football team. It plays in the Maltese 2nd Division, with home games taking place at the Ta' Qali Stadium. Marsaxlokk also has a water polo team, which dates to 1952.

Twin towns – sister cities
Marsaxlokk is twinned with:
 * 🇮🇹 Cadeo, Italy
 * 🇫🇷 Leucate, France

title: Marsaxlokk


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Digital Radio Mondiale

Digital Radio Mondiale (DRM; mondiale being Italian and French for "worldwide") is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting—particularly shortwave—and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using xHE-AAC audio coding format. Various other MPEG-4 codecs and Opus are also compatible, but the standard now specifies xHE-AAC.

Digital Radio Mondiale is also the name of the international non-profit consortium that has designed the platform and is now promoting its introduction. Radio France Internationale, TéléDiffusion de France, BBC World Service, Deutsche Welle, Voice of America, Telefunken (now Transradio) and Thomcast (now Ampegon) took part at the formation of the DRM consortium.

The principle of DRM is that bandwidth is the limiting factor, and computer processing power is cheap; modern CPU-intensive audio compression techniques enable more efficient use of available bandwidth, at the expense of processing resources.

Features

DRM can broadcast on frequencies below 30 MHz (long wave, medium wave and short wave), which allow for very-long-distance signal propagation. The modes for these lower frequencies were previously known as "DRM30". In the VHF bands, the term "DRM+" was used. DRM+ is able to use available broadcast spectra between 30 and 300 MHz; generally this means band I (47 to 68 MHz), band II (87.5 to 108 MHz) and band III (174 to 230 MHz). DRM has been designed to be able to re-use portions of existing analogue transmitter facilities such as antennas, feeders, and, especially for DRM30, the transmitters themselves, avoiding major new investment. DRM is robust against the fading and interference which often plague conventional broadcasting in these frequency ranges.

The encoding and decoding can be performed with digital signal processing, so that a low-cost embedded system with a conventional transmitter and receiver can perform the rather complex encoding and decoding.

As a digital medium, DRM can transmit other data besides the audio channels (datacasting) — as well as RDS-type metadata or program-associated data as Digital Audio Broadcasting (DAB) does. DRM services can be operated in many different network configurations, from a traditional AM one-service one-transmitter model to a multi-service (up to four) multi-transmitter model, either as a single-frequency network (SFN) or multi-frequency network (MFN). Hybrid operation, where the same transmitter delivers both analogue and DRM services simultaneously is also possible.

DRM incorporates technology known as Emergency Warning Features that can override other programming and activates radios which are in standby in order to receive emergency broadcasts.

Status
The technical standard is available free-of-charge from the ETSI, and the ITU has approved its use in most of the world. Approval for ITU region 2 is pending amendments to existing international agreements. The inaugural broadcast took place on June 16, 2003, in Geneva, Switzerland, at the ITU's World Radio Conference.

Current broadcasters include Akashvani (formerly All India Radio), BBC World Service, funklust (formerly known as BitXpress), Radio Exterior de España, Radio New Zealand International, Vatican Radio, Radio Romania International and Radio Kuwait.

Until now DRM receivers have typically used a personal computer. A few manufacturers have introduced DRM receivers which have thus far remained niche products due to limited choice of broadcasts. It is expected that the transition of national broadcasters to digital services on DRM, notably All India Radio, will stimulate the production of a new generation of affordable, and efficient receivers.

Chengdu NewStar Electronics is offering the DR111 from May 2012 on which meets the minimum requirements for DRM receivers specified by the DRM consortium and is sold worldwide.

The General Overseas Service of Akashvani broadcasts daily in DRM to Western Europe on 9.95 MHz at 17:45 to 22:30 UTC. All India Radio is in the process of replacing and refurbishing many of its domestic AM transmitters with DRM. The project which began in 2012 is scheduled to complete during 2015.

The British Broadcasting Corporation BBC has trialled the technology in the United Kingdom by broadcasting BBC Radio Devon in the Plymouth area in the MF band. The trial lasted for a year (April 2007 – April 2008). The BBC also trialed DRM+ in the FM band in 2010 from the Craigkelly transmitting station in Fife, Scotland, over an area which included the city of Edinburgh. In this trial, a 10 kW (ERP) FM transmitter was replaced with a 1 kW DRM+ transmitter in two different modes, and coverage compared with FM. Digital Radio Mondiale was included in the 2007 Ofcom consultation on the future of radio in the United Kingdom for the AM medium wave band.

RTÉ has also run single and multiple programme overnight tests during a similar period on the 252 kHz LW transmitter in Trim, County Meath, Ireland which was upgraded to support DRM after Atlantic 252 closed.

The Fraunhofer Institute for integrated circuits IIS offers a package for software defined radios which can be licensed to radio manufacturers. Software package for car radios with DRM – Digital Radio Mondiale

International regulation
On 28 September 2006, the Australian spectrum regulator, the Australian Communications and Media Authority, announced that it had "placed an embargo on frequency bands potentially suitable for use by broadcasting services using Digital Radio Mondiale until spectrum planning can be completed" "those bands being "5,950–6,200; 7,100–7,300; 9,500–9,900; 11,650–12,050; 13,600–13,800; 15,100–15,600; 17,550–17,900; 21,450–21,850 and 25,670–26,100 kHz.

Since 2005, the United States Federal Communications Commission states in that: "For digitally modulated emissions, the Digital Radio Mondiale (DRM) standard shall be employed." Part 73, section 758 is for HF broadcasting only.

Audio source coding
Useful bitrates for DRM30 range from 6.1 kbit/s (Mode D) to 34.8 kbit/s (Mode A) for a 10 kHz bandwidth (±5 kHz around the central frequency). It is possible to achieve bit rates up to 72 kbit/s (Mode A) by using a standard 20 kHz (±10 kHz) wide channel. (For comparison, pure digital HD Radio can broadcast 20 kbit/s using channels 10 kHz wide and up to 60 kbit/s using 20 kHz channels.) Useful bitrate depends also on other parameters, such as:
 * desired robustness to errors (error coding)
 * power needed (modulation scheme)
 * robustness in regard to propagation conditions (multipath propagation, doppler effect), etc.

When DRM was originally designed, it was clear that the most robust modes offered insufficient capacity for the then state-of-the-art audio coding format MPEG-4 HE-AAC (High Efficiency Advanced Audio Coding). Therefore, the standard launched with a choice of three different audio coding systems (source coding) depending on the bitrate:
 * MPEG-4 HE-AAC (High Efficiency Advanced Audio Coding). AAC is a perceptual coder suited for voice and music and the High Efficiency is an optional extension for reconstruction of high frequencies (SBR: spectral bandwidth replication) and stereo image (PS: Parametric Stereo). 24 kHz or 12 kHz sampling frequencies can be used for core AAC (no SBR) which correspond respectively to 48 kHz and 24 kHz when using SBR oversampling.
 * MPEG-4 CELP which is a parametric coder suited for voice only (vocoder) but that is robust to errors and needs a small bit rate.
 * MPEG-4 HVXC which is also a parametric coder for speech programs that uses an even smaller bitrate than CELP.

However, with the development of MPEG-4 xHE-AAC, which is an implementation of MPEG Unified Speech and Audio Coding, the DRM standard was updated and the two speech-only coding formats, CELP and HVXC, were replaced. USAC is designed to combine the properties of a speech and a general audio coding according to bandwidth constraints and so is able to handle all kinds of programme material. Given that there were few CELP and HVXC broadcasts on-air, the decision to drop the speech-only coding formats has passed without issue.

Many broadcasters still use the HE-AAC coding format because it still offers an acceptable audio quality at bitrates above about 15 kbit/s. However, it is anticipated that in future, most broadcasters will adopt xHE-AAC.

DRM30, unlike HD Radio, allows multiprogramming.

Opus
Opus is an open-source codec not included in the DRM standard, but commonly supported by popular software implementations. Aside from perceived technical advantages over the MPEG family such as low latency (delay between coding and decoding), the codec is royalty-free and not subject to patent licensing. Equipment manufacturers currently pay royalties for incorporating the MPEG codecs.

 * Since version 2.1, Dream can broadcast using Opus format.
 * Spark supports CELT transmissions, which is a subset of Opus.

Unfortunately Opus has a substantially lower audio quality than xHE-AAC at low bitrates, which are a key to conserve bandwidth. In fact, at 8 Kbps Opus actually sounds worse than analog shortwave radio. A video showing the comparison between Opus and xHE-AAC at 12 Kbps bitrate is available here.

Bandwidth

DRM broadcasting can be done using a choice of different bandwidths:
 * 4.5 kHz. Gives the ability for the broadcaster to do a simulcast and use the lower-sideband area of a 9 kHz raster channel for AM, with a 4.5 kHz DRM signal occupying the area traditionally taken by the upper-sideband. However the resulting bit rate and audio quality is not good.
 * 5 kHz. Gives the ability for the broadcaster to do a simulcast and use the lower-sideband area of a 10 kHz raster channel for AM, with a 5 kHz DRM signal occupying the area traditionally taken by the upper-sideband. However the resulting bit rate and audio quality is marginal (7.1–16.7 kbit/s for 5 kHz). This technique could be used on the shortwave bands throughout the world.
 * 9 kHz. Occupies half the standard bandwidth of a region 1 long wave or medium wave broadcast channel.
 * 10 kHz. Occupies half the standard bandwidth of a region 2 broadcast channel, and could be used to simulcast with analogue audio channel restricted to NRSC5. Occupies a full worldwide short wave broadcast channel (giving 14.8–34.8 kbit/s).
 * 18 kHz. Occupies full bandwidth of region 1 long wave or medium wave channels according to the existing frequency plan. This offers better audio quality.
 * 20 kHz. Occupies full bandwidth of region 2 or region 3 AM channel according to the existing frequency plan. This offers highest audio quality of the DRM30 standard (giving 30.6–72 kbit/s).
 * 100 kHz for DRM+. This bandwidth can be used in band I, II, and III and DRM+ can transmit four different programs in this bandwidth or even one low definition digital video channel.

Modulation
The modulation used for DRM is coded orthogonal frequency division multiplexing (COFDM), where every carrier is modulated with quadrature amplitude modulation (QAM) with a selectable error coding.

The choice of transmission parameters depends on signal robustness wanted and propagation conditions. Transmission signal is affected by noise, interference, multipath wave propagation and Doppler effect.

It is possible to choose among several error coding schemes and several modulation patterns: 64-QAM, 16-QAM and 4-QAM. OFDM modulation has some parameters that must be adjusted depending on propagation conditions. This is the carrier spacing which will determine the robustness against Doppler effect (which cause frequencies offsets, spread: Doppler spread) and OFDM guard interval which determine robustness against multipath propagation (which cause delay offsets, spread: delay spread). The DRM consortium has determined four different profiles corresponding to typical propagation conditions:
 * A: Gaussian channel with very little multipath propagation and Doppler effect. This profile is suited for local or regional broadcasting.
 * B: multipath propagation channel. This mode is suited for medium range transmission. It is nowadays frequently used.
 * C: similar to mode B, but with better robustness to Doppler (more carrier spacing). This mode is suited for long distance transmission.
 * D: similar to mode B, but with a resistance to large delay spread and Doppler spread. This case exists with adverse propagation conditions on very long distance transmissions. The useful bit rate for this profile is decreased.

The trade-off between these profiles stands between robustness, resistance in regards to propagation conditions and useful bit rates for the service. This table presents some values depending on these profiles. The larger the carrier spacing, the more the system is resistant to Doppler effect (Doppler spread). The larger the guard interval, the greater the resistance to long multipath propagation errors (delay spread).

The resulting low-bit rate digital information is modulated using COFDM. It can run in simulcast mode by switching between DRM and AM, and it is also prepared for linking to other alternatives (e.g., DAB or FM services).

DRM has been tested successfully on shortwave, mediumwave (with 9 as well as 10 kHz channel spacing) and longwave.

There is also a lower bandwidth two-way communication version of DRM as a replacement for SSB communications on HF - note that it is not compatible with the official DRM specification. It may be possible in some future time for the 4.5 kHz bandwidth DRM version used by the Amateur Radio community to be merged with the existing DRM specification.

The Dream software will receive the commercial versions and also limited transmission mode using the FAAC AAC encoder.

Error coding
Error coding can be chosen to be more or less robust.

This table shows an example of useful bitrates depending on protection classes:
 * OFDM propagation profiles (A or B)
 * carrier modulation (16QAM or 64QAM)
 * and channel bandwidth (9 or 10 kHz)

The lower the protection class the higher the level of error correction.

DRM+

While the initial DRM standard covered the broadcasting bands below 30 MHz, the DRM consortium voted in March 2005 to begin the process of extending the system to the VHF bands up to 108 MHz.

On 31 August 2009, DRM+ (Mode E) became an official broadcasting standard with the publication of the technical specification by the European Telecommunications Standards Institute; this is effectively a new release of the whole DRM spec with the additional mode permitting operation above 30 MHz up to 174 MHz.

Wider bandwidth channels are used, which allows radio stations to use higher bit rates, thus providing higher audio quality. A 100 kHz DRM+ channel has sufficient capacity to carry one low-definition 0.7 megabit/s wide mobile TV channel: it would be feasible to distribute mobile TV over DRM+ rather than DMB or DVB-H. However, DRM+ (DRM Mode E) as designed and standardized only provides bitrates between 37.2 and 186.3 kbit/s depending on robustness level, using 4-QAM or 16-QAM modulations and 100 kHz bandwidth.

DRM+ has been successfully tested in all the VHF bands, and this gives the DRM system the widest frequency usage; it can be used in band I, II (FM-band) and III. DRM+ can coexist with DAB in band III. The ITU has published three recommendations on DRM+, known in the documents as Digital System G. This indicates the introduction of the full DRM system (DRM 30 and DRM+). ITU-R Rec. BS.1114 is the ITU recommendation for sound broadcasting in the frequency range 30 MHz to 3 GHz. DAB, HD-Radio and ISDB-T were already recommended in this document as Digital Systems A, C and F, respectively.

In 2011, the pan-European organisation Community Media Forum Europe has recommended to the European Commission that DRM+ should rather be used for small scale broadcasting (local radio, community radio) than DAB/DAB+.

title: Digital Radio Mondiale


text:
All Indian Rodeo Cowboys Association

The All Indian Rodeo Cowboys Association (AIRCA) (formerly All Indian Professional Rodeo Cowboys Association) is a Native American organization which promotes Indian rodeo. It sponsors a schedule of local rodeos mostly in Arizona, the Indian Pro Rodeo Tour, leading up to a National Finals rodeo each year in which Native American rodeo performers compete. They cooperate closely with the Central Navajo Rodeo Association (CNRA) and the New Mexico Rodeo Association (NMRA). To compete in the Finals a performer must have competed in at least 30 rodeos during that year.

The Indian National Finals Rodeo (INFR) is a competing national organization and event.

title: All Indian Rodeo Cowboys Association


text:
Indian rodeo

Indian rodeo is the rodeo subculture of Native-American rodeo athletes and, in Canada, First Nations athletes. In the United States, there are a number of regional associations and at least two national finals. In Canada, Indian rodeos share a major role in small aboriginal communities and are also featured events in larger centres with aboriginal populations. Some major rodeos in British Columbia such as the Williams Lake Stampede are, while not aboriginally-organized and unlike some Indian rodeos open to non-natives, heavily "Indian" in character and in the ranks of competitors. The Indian rodeo is sponsored by a few well known companies including the Boot Barn, Cooper Tires and Yeti.

Indian rodeos in the United States

 * The Indian National Finals Rodeo (INFR)
 * The All Indian Rodeo Cowboys Association operates in Arizona and neighboring southwestern states.

Indian rodeos in Canada

 * Lillooet Lake Rodeo, Mount Currie, British Columbia
 * Anahim Lake Stampede, or Anahim Lake Rodeo, Anahim Lake, British Columbia
 * Nazko Jamboree, Nazko, British Columbia

Indian rodeo halls of fame in the United States

 * Indian National Finals Rodeo Hall of Fame

title: Indian rodeo


text:
Resolution (music)

Resolution in western tonal music theory is the move of a note or chord from dissonance (an unstable sound) to a consonance (a more final or stable sounding one).

Dissonance, resolution, and suspense can be used to create musical interest. Where a melody or chordal pattern is expected to resolve to a certain note or chord, a different but similarly suitable note can be resolved to instead, creating an interesting and unexpected sound. For example, the deceptive cadence.

Basis
"A dissonance has its resolution when it moves to a consonance. When a resolution is delayed or is accomplished in surprising ways—when the composer plays with our sense of expectation—a feeling of drama or suspense is created."

- Roger Kamien (2008), p.41

Resolution has a strong basis in tonal music, since atonal music generally contains a more constant level of dissonance and lacks a tonal center to which to resolve. The concept of "resolution", and the degree to which resolution is "expected", is contextual as to culture and historical period. In a classical piece of the Baroque period, for example, an added sixth chord (made up of the notes C, E, G and A, for example) has a very strong need to resolve, while in a more modern work, that need is less strong - in the context of a pop or jazz piece, such a chord could comfortably end a piece and have no particular need to resolve.

Example
An example of a single dissonant note which requires resolution would be, for instance, an F during a C major chord, C–E–G, which creates a dissonance with both E and G and may resolve to either, though more usually to E (the closer pitch). This is an example of a suspended chord. In reference to chords and progressions for example, a phrase ending with the following cadence IV–V, a half cadence, does not have a high degree of resolution. However, if this cadence were changed to (IV–)V–I, an authentic cadence, it would resolve much more strongly by ending on the tonic I chord.

title: Resolution (music)


text:
Talk:Cleanroom

Untitled
The first meaning of "cleanroom" for software engineering? I am skeptical.

the article is a double: Clean room

This should be a disambiguation page to the existing clean_room and clean_room_design pages.

Wiki Education Foundation-supported course assignment
This article was the subject of a Wiki Education Foundation-supported course assignment, between 24 January 2020 and 17 April 2020. Further details are available on the course page. Student editor(s): Mardebru, Broenk28, Willettbrock, Vkacey, CatMChapin, Samarhahmad, Christian.lumaj, Desjardc.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 17:48, 16 January 2022 (UTC)

There should be a disambiguation page
Just that: there should be a disambiguation page. Industrial "clean room" has nothing to do with the Software Engineering meaning.

 * I've split Cleanroom(Software Engineering) to a separate article and added disambiguation links on top of both pages.Skydiver 13:42, 7 December 2005 (UTC)

Cleanroom class comparison
The cleanroom class comparison is off by about a factor of 35. Either fix or ditch :-) --Ihope127 21:54, 3 October 2005 (UTC)

It's now off by only a factor of 3.5. --User:driscolj

Need history
This page should include the history of clean rooms. Part of it involves Willis Whitfield, whose story is shared at this link: http://www.hsutx.edu/advancement/news/hol/06-whitfield.htm

 * More links:
 * http://www.networkworld.com/community/node/81860
 * http://obits.abqjournal.com/obits/show/230629
 * • Sbmeirow  •  Talk  •  10:11, 27 November 2012 (UTC)

New Table to do
British standards (BS 5295) need to be totally corrected using these sources: http://www.sizes.com/built/clean_rooms.htm http://www.mssl.ucl.ac.uk/www_cleanroom/cleanroom/cr_standards.html#bs5295 http://www.cleanrooms-ireland.ie/index.cfm/fuseaction/standards.content/id/8278F54D-6B07-4DE0-B764D799BFBF5599.cfm Kar.ma 11:18, 2 June 2007 (UTC)

Confusion over particles per cubic meter and particles per cubic foot
This page refers to number of particles per cubic meter and particles per cubic foot. Only one should be correct

12.104.148.20 15:27, 19 September 2007 (UTC)

Notable facilities
Our article on biosafety levels has a list of BSL-4 facilities (those with the most stringent specifications). This article would benefit from a list of the most highly specified cleanrooms. A quick google turns up something about an ISO class 1 cleanroom being built, so can anyone incorporate a list of facilities built to the highest standards? Rovaniemi-5 (talk) 18:33, 27 April 2008 (UTC)

Huh?
This sentence:

"To give perspective, the ambient air outside in a typical urban environment might contain as many as 35,000,000 particles per cubic meter, 0.5 μm and larger in diameter, corresponding to an ISO 9 cleanroom."

...makes absolutely no sense to me. I have no idea what an ISO is. There are plenty of ISOs but none are referred to or specified in the first paragraph. I have no idea what 9 means i.e. "ISO 9" except that it must be as dirty as the air outside in a city. That doesn't sound "clean" to me. So why is it mentioned as a cleanroom score? What is the scale we are working with? Is "1" clean and 10 dirty? Or is 1 particle-free and 100 = a clod of tightly packed dirt"? Is the "typical city" Paris or Omaha or Bejing?

This first paragraph has the bizarre distinction of being both totally unclear to the cleanroom novice and also horribly written if penned by someone with enough of an education to be an "expert". 70.143.75.66 (talk) 07:00, 12 March 2009 (UTC)
 * ISO 9, I suppose, it's ISO 14644-9 «Classification of Surface Particle Cleanliness». 89.222.152.170 (talk) 17:13, 20 May 2009 (UTC)

What About Medical Cleanrooms?
Perhaps the search "Cleanroom" should direct to a disambiguation page, with a link to this article, and the article on medical isolation rooms, as some hospitals call their isolation rooms "cleanrooms"96.230.195.138 (talk) 22:20, 28 February 2010 (UTC)

Is there an estimate of the number of clean rooms (per standard) in the world? —Preceding unsigned comment added by Fulldecent (talk • contribs) 15:02, 9 March 2010 (UTC)

More info about the red links of......
pharmaceutical cleanroom --222.67.201.48 (talk) 06:39, 8 October 2010 (UTC)
 * http://scholar.google.com.au/scholar?as_q=cleanroom+pharmaceutical&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=title&as_sauthors=&as_publication=&as_ylo=&as_yhi=&as_sdt=1.&as_sdtp=on&as_sdts=5&hl=en

--222.67.201.48 (talk) 06:50, 8 October 2010 (UTC)
 * Clean room worker -- http://scholar.google.com.au/scholar?hl=en&q=allintitle%3A+clean+room+workers&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

--222.67.201.48 (talk) 06:51, 8 October 2010 (UTC)
 * http://scholar.google.com.au/scholar?hl=en&q=allintitle%3A+cleanroom+workers&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

Specifications
--222.67.201.48 (talk) 06:55, 8 October 2010 (UTC)
 * http://scholar.google.com.au/scholar?as_q=cleanroom+specification&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=title&as_sauthors=&as_publication=&as_ylo=&as_yhi=&as_sdt=1.&as_sdtp=on&as_sdts=5&hl=en

--222.67.201.48 (talk) 06:56, 8 October 2010 (UTC)
 * http://scholar.google.com.au/scholar?hl=en&q=allintitle%3A+cleanroom+specifications&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

--222.67.201.48 (talk) 06:58, 8 October 2010 (UTC)
 * http://scholar.google.com.au/scholar?hl=en&q=allintitle%3A+clean+room+specifications&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

--222.67.201.48 (talk) 06:59, 8 October 2010 (UTC)
 * http://scholar.google.com.au/scholar?hl=en&q=allintitle%3A+clean+room+specification&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

--222.67.201.48 (talk) 07:10, 8 October 2010 (UTC)
 * http://www.iso.org/iso/search.htm?qt=cleanroom&sort=rel&type=simple&published=on

Safety

 * http://scholar.google.com.hk/scholar?hl=en&q=allintitle%3A+clean+room+safety&btnG=Search&as_sdt=2000&as_ylo=&as_vis=0

--222.67.201.48 (talk) 07:16, 8 October 2010 (UTC)
 * http://scholar.google.com.hk/scholar?as_q=cleanroom+safety&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=title&as_sauthors=&as_publication=&as_ylo=&as_yhi=&as_sdt=1.&as_sdtp=on&as_sdts=5&hl=en

Health Issues from Working in a Clean Room Environment
Can one have health issues in a clean room?? Room is controlled by temp and humidity. Everything is stainless steel....vacuumm coating of medical devices. Using silane chemistry and parylene chemistry...lots of al cohol. High static electricity in the room. Use nitrogen to clean medical devices. Any danger to ones health? Have red eyes...skin problems, brittle hair, etc. since working in this environment. We wear hair nets, Tyvek suits, laytex gloves, foot covers and beard guards. — Preceding unsigned comment added by 50.90.148.176 (talk) 03:09, 3 March 2012 (UTC)

GMP EU classification
The values given in the table for GMP EU classification do not correspond with values in the source article. Can someone double check these with legislation and correct (if necessary)

Possible new photos
I have uploaded two photos of the photolithography cleanroom at the London Centre for Nanotechnology onto Wikimedia Commons.

I would propose that one of these could perhaps replace the (low res) photolithography cleanroom pic currently at the top of this article.

However I leave the decision to another editor - I work for the LCN's parent organisation and want to avoid any suggestion of conflict of interest.

Uclmaps (talk) 09:38, 22 August 2013 (UTC)

 * I like the first one and think it's better than the current lead image. Andy Dingley (talk) 10:21, 22 August 2013 (UTC)
 * The current one is too grainy, though it does show more of the room. I'd support replacing it with the first image, here. -PC-XT+ 05:06, 23 August 2013 (UTC)

Removed: Environmental benefits of cleanrooms

 * ==Environmental benefits of cleanrooms==
 * Cleanrooms offer many environmental benefits that traditional construction often eschews. Modular Cleanrooms provide a re-usable space that saves money on energy, is recyclable and minimizes waste by reducing on-site construction.

I removed the above because it was uncited and made no sense to me. In fact, because of the energy-intensive air handling required for a clean room, I wouldn't expect it to have environmental benefits. If somebody can make it clearer what it's talking about, or find a reference for it, feel free to add it back. 45.37.166.153 (talk) 19:23, 1 April 2016 (UTC)

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Maybe we should add a section on unconventional/unintuitive applications of cleanroom tech?
There are certain applications of cleanrooms which I know, but don't have references to. Some of them quite titillating. And since there Can Be More Than One, maybe they'd warrant their own section, or at least see-also -links. Some examples of which I'm privy to are:

 * The so called Bubble Children. Severely immunocompromised medical patients, most tragically those who inherited the compromise from birth, have to be kept in (sterile) cleanroom conditions throughout their life in order for them to survive.
 * Deep-core archeology. When we bore into deep ice sheets, in order to understand earlier conditions on the Earth, both the boring process and the subsequent preservation of the bore itself have to be done in sterile conditions, in order to avoid contamination by modern day biome.
 * Planetary exploration with regard to exobiological concerns. Each and every probe we send out into the solar system has to be thoroughly sterilized and handled in a cleanroom, not just to avoid contaminating any sample return mission with our lifeforms, but also to avoid contaminating any of the bodies we've contacted. This has been procedure since the first missions to the Moon, and I believe is international law by now.
 * Nuclear powerplants. The whole of them are structured as (low-grade, but very real and well-engineered) cleanrooms. The buildings, the procedures, everything is structured around not spreading around radioactive particulates -- complete with inverse pressure through HEPA filters, checkpoints where you have to change your shoes, totally paranoid measurement of radiation levels *and* other particulates (which might become neutron activated and/or carry activation products further by contact), and so on. That one "chimney" you often see sticking out of their roof? It's the centralized exhaust vent from the plant/cleanroom's air filtering system, which is raised into the air; so that in case *everything* else fails, at least the radioactive exhaust gets spread a little thinner, and flies farther away, so that it can decay before it rains down.
 * Also, anything having to do with a neutron flux. Because neutron activation products are nasty. In nuclear technology, the best way to avoid activation products, is to make pretty darn sure you don't have anything to activate, to begin with. Hence, again, clean rooms.
 * In medicine, isolation wards are effectively clean rooms. Even if their primary function, as in the case of nuclear powerplants, is to stop something from escaping from the room, again, it's also to stop something from gaining ingress as well. Thus, the technology is much the same. * And by the way, every time someone goes into a controlled atmosphere room and goes out of it, you have two acts in two different directions. This is seen especially starkly in the highest varieties of biolabs, studying the most harmful and contagious of organisms, the level-4 labs. Those who handle Ebola, Smallpox, and whatnot. There the technology is as much about not letting something out, as about not letting something in. Maybe this would even warrant its own chapter in the article...might write it myself.

˝˝˝˝ — Preceding unsigned comment added by Decoy (talk • contribs) 00:43, 7 November 2021 (UTC)

William (Bill) C. McElroy Jr. resume
In the History section, the last paragraph seems to be Bill McElroy Jr. adding his own resume to Wikipedia, as the only reference to the entire paragraph is just his own name and title, without a link to a third party reference or citation. I'm thinking the paragraph needs to be properly sourced or deleted. Gentgeen (talk) 21:21, 9 February 2022 (UTC)

Concerning: Good Article Nomination
This article is being nominated for good article status. Please direct all participation queries to the Wikipedia Good Articles nominations templates to participate. Habatchii (talk) 23:14, 29 December 2022 (UTC)

title: Talk:Cleanroom


text:
Digital radio

Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services.

Types
In digital broadcasting systems, the analog audio signal is digitized, compressed using an audio coding format such as AAC+ (MDCT) or MP2, and transmitted using a digital modulation scheme. The aim is to increase the number of radio programs in a given spectrum, to improve the audio quality, to eliminate fading problems in mobile environments, to allow additional datacasting services, and to decrease the transmission power or the number of transmitters required to cover a region. However, analog radio (AM and FM) is still more popular and listening to radio over IP (Internet Protocol) is growing in popularity.

In 2012 four digital wireless radio systems are recognized by the International Telecommunication Union: the two European systems Digital Audio Broadcasting (DAB) and Digital Radio Mondiale (DRM), the Japanese ISDB-T and the in-band on-channel technique used in the US and Arab world and branded as HD Radio.

An older definition, still used in communication engineering literature, is wireless digital transmission technologies, i.e. microwave and radio frequency communication standards where analog information signals as well as digital data are carried by a digital signal, by means of a digital modulation method. This definition includes broadcasting systems such as digital TV and digital radio broadcasting, but also two-way digital radio standards such as the second generation (2G) cell-phones and later, short-range communication such as digital cordless phones, wireless computer networks, digital micro-wave radio links, deep space communication systems such as communications to and from the two Voyager space probes, etc.

Broadcast standards
Digital audio radio service standards may provide terrestrial or satellite radio service. Digital radio broadcasting systems are typically designed for handheld mobile devices, like mobile-TV systems and unlike other digital TV systems which typically require a fixed directional antenna. Some digital radio systems provide in-band on-channel (IBOC) solutions that may coexist with or simulcast with analog AM or FM transmissions, while others are designed for designated radio frequency bands. The latter allows one wideband radio signal to carry a multiplex of several radio-channels of various bitrates as well as data services and other forms of media. Some digital broadcasting systems allow single-frequency network (SFN), where all terrestrial transmitters in a region sending the same multiplex of radio programs may use the same frequency channel without self-interference problems, further improving the system spectral efficiency.

While digital broadcasting offers many potential benefits, its introduction has been hindered by a lack of global agreement on standards and many disadvantages. The DAB Eureka 147 standard for digital radio is coordinated by the World DMB Forum. This standard of digital radio technology was defined in the late 1980s, and is now being introduced in some European countries. Commercial DAB receivers began to be sold in 1999 and, by 2006, 500 million people were in the coverage area of DAB broadcasts, although by this time sales had only taken off in the UK and Denmark. In 2006 there are approximately 1,000 DAB stations in operation. There have been criticisms of the Eureka 147 standard and so a new 'DAB+' standard has been introduced.

The DRM standard has been used for several years to broadcast digitally on frequencies below 30 MHz (shortwave, mediumwave and longwave). Also there is now the extended standard DRM+, which is designed for VHF bands. Tests of DRM+ has been made in countries such as in Brazil, Germany, France, India, Sri Lanka, the UK, Slovakia, Italy (incl. the Vatican), as well as Sweden.

DRM+ is regarded as a more transparent and less costly standard than DAB+ and thus a better choice for local radio ; commercial or community broadcasters. Although DAB+ has been introduced in Australia the government concluded in 2011 that a preference for DRM and DRM+ above HD Radio could be used to supplement DAB+ services in (some) local and regional areas.

To date the following standards have been defined for one-way digital radio:

Digital audio broadcasting systems

 * Eureka 147 (branded as DAB)
 * DAB+
 * ISDB-TSB
 * Internet radio (Technically not a true Broadcast system)
 * T-DMB V-Radio
 * FM band in-band on-channel (FM IBOC):
 * HD Radio (OFDM modulation over FM and AM band IBOC sidebands)
 * FMeXtra (FM band IBOC subcarriers)
 * Digital Radio Mondiale extension (DRM+) (OFDM modulation over AM band IBOC sidebands)
 * Convergent Digital Radio (CDR) (OFDM modulation over FM band IBOC sidebands)
 * AM band in-band on-channel (AM IBOC):
 * HD Radio (AM IBOC sideband)
 * Digital Radio Mondiale (branded as DRM) for the short, medium and long wave-bands
 * Satellite radio:
 * WorldSpace in Asia and Africa
 * Sirius XM Radio in North America
 * MobaHo! in Japan and the Republic of (South) Korea
 * Systems also designed for digital TV:
 * DMB
 * DVB-H
 * ISDB-T
 * DTMB
 * Low-bandwidth digital data broadcasting over existing FM radio:
 * Radio Data System (branded as RDS)
 * Radio pagers:
 * FLEX
 * ReFLEX
 * POCSAG
 * NTT

Digital television (DTV) broadcasting systems

 * Digital Video Broadcasting (DVB)
 * Integrated Services Digital Broadcasting (ISDB)
 * Digital Multimedia Broadcasting (DMB)
 * Digital Terrestrial Television (DTTV or DTT) to fixed mainly roof-top antennas:
 * DVB-T (based on OFDM modulation)
 * ISDB-T (based on OFDM modulation)
 * ATSC (based on 8VSB modulation)
 * T-DMB (based on OFDM modulation)
 * Digital Terrestrial Multimedia Broadcast (DTMB) (based on OFDM modulation)
 * Mobile TV reception in handheld devices:
 * DVB-H (based on OFDM modulation)
 * MediaFLO (based on OFDM modulation)
 * DMB (based on OFDM modulation)
 * Multimedia Broadcast Multicast Service (MBMS) via the GSM EDGE and UMTS cellular networks
 * DVB-SH (based on OFDM modulation)
 * China Multimedia Mobile Broadcasting (CMMB) (based on OFDM modulation)
 * Satellite TV:
 * DVB-S (for Satellite TV)
 * ISDB-S
 * 4DTV
 * S-DMB
 * MobaHo!
 * Advanced Broadcasting System-Satellite (ABS-S)

See also software radio for a discussion of radios which use digital signal processing.

DAB adopters
Digital Audio Broadcasting (DAB), also known as Eureka 147, has been adopted by around 20 countries worldwide. It is based on the MPEG-1 Audio Layer II audio coding format and this has been co-ordinated by the WorldDMB.

WorldDMB announced in November 2006 that DAB would be adopting the HE-AACv2 audio coding format, also known as eAAC+. Also being adopted are the MPEG Surround format, and stronger error correction coding called Reed–Solomon coding. The update has been named DAB+. Receivers that support the new DAB standard began being released during 2007 with firmware updated available for some older receivers.

DAB and DAB+ cannot be used for mobile TV because they do not include any video codecs. DAB related standards Digital Multimedia Broadcasting (DMB) and DAB-IP are suitable for mobile radio and TV both because they have MPEG 4 AVC and WMV9 respectively as video coding formats. However a DMB video sub-channel can easily be added to any DAB transmission - as DMB was designed from the outset to be carried on a DAB subchannel. DMB broadcasts in Korea carry conventional MPEG 1 Layer II DAB audio services alongside their DMB video services.

Australia
Australia commenced regular digital audio broadcasting using the DAB+ standard on 4 May 2009, after many years of trialling alternative systems. Normal radio services operate on the AM and FM bands, as well as four stations (ABC and SBS) on digital TV channels. The services are currently operating in the five state capital cities: Adelaide, Brisbane, Melbourne, Perth and Sydney, and is being trialled in Canberra and Darwin.

Canada
Canada has begun allowing experimental HD Radio broadcasts in December 2012 and digital audio subchannels on a case-by-case basis, with the first stations in the country being CFRM-FM in Little Current, CING-FM in Hamilton, and CJSA-FM in Toronto (with a fourth, CFMS-FM in the Toronto suburb of Markham applying to operate HD Radio technology), all within the province of Ontario.

Germany
In 2020, DAB+ signals cover more than 90% of Germany. A national multiplex contains three public stations by Deutschlandfunk and 12 commercial stations. In most areas, additional multiplexes with public broadcasters and regional commercial stations are available.

The first DAB station network was deployed in Bavaria since 17 October 1995 until full coverage in 1999. Other states had funded a station network but the lack of success led them to scrap the funding - the MDR switched off in 1998 already and Brandenburg declared a failure in 2004. Instead Berlin/Brandenburg began to switch to digital radio based on an audio-only DVB-T mode given the success of the DVB-T standard in the region when earlier analogue television was switched off in August 2003 (being the first region to switch in Germany). During that time the DVB-H variant of the DVB family was released for transmission to mobile receivers in 2004. During 2005 most radio stations left the DAB network with only one public service broadcaster ensemble to remain in the now fully state-funded station network. At last the Kommission zur Ermittlung des Finanzbedarfs der Rundfunkanstalten (commission to determine the financial needs of broadcasters) blocked federal funding on 15. July 2009 until economic viability of DAB broadcasting would be proven - and pointing to DVB-T as a viable alternative.

Digital radio deployment was rebooted during 2011 - a joint commission of public and private radio broadcasters decided upon "DAB+" as the new national standard in December 2010. The new station network started as planned on 1. August 2011 with 27 stations with 10 kW each giving a coverage of 70% across the nation. A single "Bundesmux" ("fed-mux": short for "federal multiplex") was created on band 5C as a single-frequency network on channel 5C (see ). With the initial market success of DAB+ the contractors decided on an expansion of the digital radio station network in November 2012.

Korea
On 1 December 2005 South Korea launched its T-DMB service which includes both television and radio stations. T-DMB is a derivative of DAB with specifications published by ETSI. More than 110,000 receivers had been sold in one month only in 2005.

Hong Kong
Hong Kong replaced DAB with DVB-T2 Lite.

Norway
Norway was the first country where analog FM radio was switched off in 2017 being replaced by nationwide DAB+ distribution.

Local stations can continue broadcasting in FM.

Other European Countries
With DAB being available across Belgium, Netherlands, Switzerland, Denmark, Norway and Northern Italy there is good coverage across the European Backbone area (see countries using DAB/DMB) indicating a sufficient momentum on the market. France, Spain, Sweden and Poland use DAB+ only in the big cities.

Portugal and Finland abandoned DAB. Finland is requesting the EU to mandate that automakers support FM similarly to DAB.

Japan
Japan has started terrestrial sound broadcasting using ISDB-Tsb and MobaHO! 2.6 GHz Satellite Sound digital broadcasting

United Kingdom
In the United Kingdom, 44.3% of the population now has a DAB digital radio set and 34.4% of listening is to different digital platforms. Because of the early success of the old DAB standard, the transition to the more efficient DAB+ takes more time. If DAB was switched off, older receivers would become worthless. In 2020, about half of the stations in the UK use DAB+.

26 million people, or 39.6% of the population of 65.64 million, now tune into digital radio each week, up 2.6 million year on year, according to RAJAR in Q1 2013. But FM listening has increased to 61% and DAB decreased to 21% DAB listeners may also use AM & FM too.

The UK currently has the world's biggest digital radio network, with about 500 transmitters, two nationwide DAB ensembles and 48 local and regional DAB ensembles, broadcasting over 250 commercial and 34 BBC radio stations; about 100 stations can be received in London. On DAB digital radio most listeners can receive around 30 additional stations.

Digital radio stations are also distributed on digital television platforms such as Sky, Virgin Media and Freeview, as well as internet radio.

The Government will make a decision on a radio switchover subject to listening and coverage criteria being met. A digital radio switchover would maintain FM as a platform, while moving some services to DAB-only distribution.

DAB+ devices in the UK has been available to the public by 2010

United States
The United States has opted for the proprietary HD Radio technology, a type of in-band on-channel (IBOC) technology. According to iBiquity, "HD Radio" is the company's trade name for its proprietary digital radio system, but the name does not imply either high definition or "hybrid digital" as it is commonly incorrectly referenced.

Transmissions use orthogonal frequency-division multiplexing, a technique which is also used for European terrestrial digital TV broadcast (DVB-T). HD Radio technology was developed and is licensed by iBiquity Digital Corporation. It is widely believed that a major reason for HD radio technology is to offer some limited digital radio services while preserving the relative "stick values" of the stations involved and to ensure that new programming services will be controlled by existing licensees.

The FM digital schemes in the U.S. provide audio at rates from 96 to 128 kilobits per second (kbit/s), with auxiliary "subcarrier" transmissions at up to 64 kbit/s. The AM digital schemes have data rates of about 48 kbit/s, with auxiliary services provided at a much lower data rate. Both the FM and AM schemes use lossy compression techniques to make the best use of the limited bandwidth.

Lucent Digital Radio, USA Digital Radio (USADR), and Digital Radio Express commenced tests in 1999 of their various schemes for digital broadcast, with the expectation that they would report their results to the National Radio Systems Committee (NRSC) in December 1999. Results of these tests remain unclear, which in general describes the status of the terrestrial digital radio broadcasting effort in North America.

While traditional terrestrial radio broadcasters are trying to "go digital", most major US automobile manufacturers are promoting digital satellite radio. HD Radio technology has also made inroads in the automotive sector with factory-installed options announced by BMW, Ford, Hyundai, Jaguar, Lincoln, Mercedes, MINI, and Volvo.

Satellite radio is distinguished by its freedom from FCC censorship in the United States, its relative lack of advertising, and its ability to allow people on the road to listen to the same stations at any location in the country. Listeners must currently pay an annual or monthly subscription fee in order to access the service.

Sirius Satellite Radio launched a constellation of three Sirius satellites during the course of 2000. The satellites were built by Space Systems/Loral and were launched by Russian Proton boosters. As with XM Satellite Radio, Sirius implemented a series of terrestrial ground repeaters where satellite signal would otherwise be blocked by large structures including natural structures and high-rise buildings.

XM Satellite Radio has a constellation of three satellites, two of which were launched in the spring of 2001, with one following later in 2005. The satellites are Boeing 702 comsats, and were put into orbit by Sea Launch boosters. Back-up ground transmitters (repeaters) will be built in cities where satellite signals could be blocked by big buildings.

On February 19, 2007, Sirius Satellite Radio and XM Satellite Radio merged, to form Sirius XM Radio.

The FCC has auctioned bandwidth allocations for satellite broadcast in the S band range, around 2.3 GHz.

Terrestrial broadcasting has advantages in being free and local. Satellite radio is neither of these things; however, in the early 21st century it has grown by providing uncensored content (most notably, the crossover of Howard Stern from terrestrial radio to satellite radio) and commercial-free, all-digital music channels that offer similar radio formats to local stations.

The "HD Radio" signal of an FM broadcast station in the US has a limited listening distance from the broadcast tower site. FCC regulations currently limit the power of the digital part of the station's transmission to 10% of the existing analog power permitted the station. Even at this power level, the presence of the digital signal right next to the station's analog signal can result in older radios picking up noise due to trouble rejecting the adjacent digital signal. "There are still some concerns that HD Radio on FM will increase interference between different stations even though HD Radio at the 10% power level fits within the FCC spectral mask." HD Radio HD Radio.

"HD Radio" allows each existing broadcast station to add additional "channels" in the US by transmitting a digital signal on both sides of its channel, just beyond their existing analog Frequency Modulation signal. The HD Radio signal occupies the 0.1 MHz that begins 0.1 MHz above and below the carrier frequency station. For instance, if a station's analog signal's carrier frequency is 93.3 MHz, the digital signal will fill 93.1–93.2 MHz and 93.4–93.5 MHz within the FM Broadcast Band. Several digital audio streams, or "subchannels", can be carried within this single digital data stream, with the number of audio of subchannels and bandwidth allocations at the choice of the station. On the radio tuner, these will appear as (in the above case) "93.3-2", "93.3-3", and so on. The frequencies that are used do not change as more channels are added to the one radio station (93.3 MHz in the example above). Instead, a fixed total amount of bandwidth is simply reallocated across the audio streams such that each now receives less bandwidth, and therefore lower audio quality, than before.

There is no federally mandated transition to HD Radio for both FM and AM Stations. However, on October 27, 2020, the FCC approved voluntary all-digital AM operation nationwide.

Developing nations
Digital radio is now being provided to the developing world. A satellite communications company named WorldSpace was setting up a network of three satellites, including "AfriStar", "AsiaStar", and "AmeriStar", to provide digital audio information services to Africa, Asia, and Latin America. AfriStar and AsiaStar are in orbit. AmeriStar cannot be launched from the United States as Worldspace transmits on the L-band and would interfere with USA military as mentioned above.. in its heyday provided service to over 170,000 subscribers in eastern and southern Africa, the Middle East, and much of Asia with 96% coming from India. Timbre Media along with Saregama India plan to relaunch the company. As of 2013 Worldspace is defunct, but two satellites are in orbit which still have a few channels. See main WorldSpace article.

Each satellite provides three transmission beams that can support 50 channels each, carrying news, music, entertainment, and education, and including a computer multimedia service. Local, regional, and international broadcasters were working with WorldStar to provide services.

A consortium of broadcasters and equipment manufacturers are also working to bring the benefits of digital broadcasting to the radio spectrum currently used for terrestrial AM radio broadcasts, including international shortwave transmissions. Over seventy broadcasters are now transmitting programs using the new standard, known as Digital Radio Mondiale (DRM), and / commercial DRM receivers are available (though there are few models on the DRM website and some are discontinued). DRM's system uses the MPEG-4 based standard aacPlus to code the music and CELP or HVXC for speech programs. At present these are priced too high to be affordable by many in the third world, however. Take-up of DRM has been minuscule and many traditional Shortwave broadcasters now only stream on Internet, use fixed satellite (TV set-boxes) or Local Analogue FM relays to save on costs. Very few (expensive) DRM radio sets are available and some Broadcasters (RTE in Ireland on 252 kHz) have ceased trials without launching a service.

Low-cost DAB radio receivers are now available from various Japanese manufacturers, and WorldSpace has worked with Thomson Broadcast to introduce a village communications center known as a Telekiosk to bring communications services to rural areas. The Telekiosks are self-contained and are available as fixed or mobile units

Two-way digital radio standards
The key breakthrough or key feature in digital radio transmission systems is that they allow lower transmission power, they can provide robustness to noise and cross-talk and other forms of interference, and thus allow the same radio frequency to be reused at shorter distance. Consequently, the spectral efficiency (the number of phonecalls per MHz and base station, or the number of bit/s per Hz and transmitter, etc.) may be sufficiently increased. Digital radio transmission can also carry any kind of information whatsoever — just as long at it has been expressed digitally. Earlier radio communication systems had to be made expressly for a given form of communications: telephone, telegraph, or television, for example. All kinds of digital communications can be multiplexed or encrypted at will.
 * Digital cellular telephony (2G systems and later generations):
 * GSM
 * UMTS (sometimes called W-CDMA)
 * TETRA
 * IS-95 (cdmaOne)
 * IS-136 (D-AMPS, sometimes called TDMA)
 * IS-2000 (CDMA2000)
 * iDEN
 * Digital Mobile Radio:
 * Project 25 a.k.a. "P25" or "APCO-25"
 * TETRA
 * TETRAPOL
 * NXDN/dPMR
 * DMR
 * D-STAR
 * Wireless networking:
 * Wi-Fi
 * HIPERLAN
 * Bluetooth
 * DASH7
 * Zigbee
 * 6LoWPAN
 * Military radio systems for Network-centric warfare
 * JTRS (Joint Tactical Radio System- a flexible software-defined radio)
 * SINCGARS (Single channel ground to air radio system)
 * Amateur packet radio:
 * AX.25
 * Digital modems for HF:
 * PACTOR
 * Satellite radio:
 * Satmodems
 * Wireless local loop:
 * Basic Exchange Telephone Radio Service
 * Broadband wireless access:
 * IEEE 802.16

title: Digital radio


text:
Talk:QANTAS

Please do not delete. QANTAS isn't misspelled, it's all capitalized because it's the abbreviation for the Queensland And Northern Territory Air Service... Thanks Dysprosia 11:08 23 Jul 2003 (UTC)

 * Restored - how could anyone possible think QANTAS was a misspelling... How do they get to and from Australia? כסיף Cyp 11:24 23 Jul 2003 (UTC)

The name is Qantas. As any schoolboy knows, it was an abbreviation—in 1922. It is not an abbreviation now and has not been for many, many years. This page should be deleted. Tannin 11:36 23 Jul 2003 (UTC)

 * The point is, it was an abbreviation, and we capitalize abbreviations, and should still be here incase anyone links to the Qantas article using QANTAS . It's not linked up though, yet, but still, it may...
 * Anyway, even QANTAS themselves write it all uppercase on their livery ;)
 * I don't know, now... Dysprosia 11:43 23 Jul 2003 (UTC)

 * No they don't. See for yourself: www.qantas.com. Tannin
 * On the logo, and on the aircraft themselves, they have it capitalized, but as you say, in referring in text to themselves, they do use Qantas. Dysprosia

Either way, I'm impartial (or at least consider myself to be impartial), just assumed deleting it was by accident. (Didn't know miscapitalizations were also misspellings.) כסיף Cyp 12:22 23 Jul 2003 (UTC)

I'd vote for keeping it, in line with the general policy of making common misspellings into redirects to the correct spelling. Vicki Rosenzweig 13:10 23 Jul 2003 (UTC)

title: Talk:QANTAS


text:
Talk:Duke

Duchy vs Dukedom
"A duchy is the territory or geopolitical entity ruled by a duke, whereas his title or area is often called a dukedom."

This sentence isn't sourced and contradicts the Duchy article.

OED online, Cambridge Dictionary, and Collins English Dictionary all support the Duchy article that both terms can be used to refer to the land held by a Duke. IJMacD (talk) 07:06, 30 July 2023 (UTC)

title: Talk:Duke


text:
Wezep

Wezep is a town in the municipality of Oldebroek, Netherlands. Located in the province of Gelderland, it had about 13,500 inhabitants in 2012. The Wezep railway station, located on the Utrecht–Zwolle railway, is the town's main landmark. The municipality's TV station is called LOCO TV.

Sports
Wezep has several sport clubs.

Notable residents

 * Jan Terlouw (born 1931), physicist, author and politician
 * Lana Wolf (born 1975), singer

Economy
The Plukon Food Group, one of the largest poultry meat companies in Europe, has its headquarters in Wezep.

title: Wezep


text:
Talk:MDM

Is any other person visiting this site? then get in touch. Mail me at tech2G@uboot.com. The point of discussion is the difference between an inverse mux and a demux. Hey, you got guts? Get in touch with me, then. I could even give you some reward, in cash or kind if you impress me :)

title: Talk:MDM


text:
Shackle

A shackle (or shacklebolt), also known as a gyve, is a U-shaped piece of metal secured with a clevis pin or bolt across the opening, or a hinged metal loop secured with a quick-release locking pin mechanism. The term also applies to handcuffs and other similarly conceived restraint devices that function in a similar manner. Shackles are the primary connecting link in all manner of rigging systems, from boats and ships to industrial crane rigging, as they allow different rigging subsets to be connected or disconnected quickly. A shackle is also the similarly shaped piece of metal used with a locking mechanism in padlocks. A carabiner is a type of shackle used in mountaineering.

Bow shackle
With a larger "O" shape to the loop, this shackle can take loads from many directions without developing as much side load. However, the larger shape to the loop does reduce its overall strength. Also referred to as an anchor shackle.

D-shackle
Also known as a chain shackle, D-shackles are narrow shackles shaped like a loop of chain, usually with a pin or threaded pin closure. D-shackles are very common and most other shackle types are a variation of the D-shackle. The small loop can take high loads primarily in line. Side and racking loads may twist or bend a D-shackle.

Headboard shackle
This longer version of a D-shackle is used to attach halyards to sails, especially sails fitted with a headboard such as on Bermuda rigged boats. Headboard shackles are often stamped from flat strap stainless steel, and feature an additional pin between the top of the loop and the bottom so the headboard does not chafe the spliced eye of the halyard.

Pin shackle
A pin shackle is closed with an anchor bolt and cotter pin, in a manner similar to a clevis. It is for this reason they are often referred to, in industrial jargon, as clevises. Pin shackles can be inconvenient to work with, at times, as the bolt will need to be secured to the shackle body to avoid its loss, usually with a split pin or seizing wire. A more secure version used in crane rigging features the combination of a securing nut (hardware) located alongside the cotter pin. Pin shackles are practical in many rigging applications where the anchor bolt is expected to experience some rotation.

Snap shackle

As the name implies, a snap shackle is a fast action fastener which can be implemented single-handedly. It uses a spring-activated locking mechanism to close a hinged shackle, and can be unfastened under load. This is a potential safety hazard, but can also be extremely useful at times. The snap shackle is not as secure as any other form of shackle, but can come in handy for temporary uses or in situations which must be moved or replaced often, such as a sailor's harness tether or to attach spinnaker sheets. Note: When this type of shackle is used to release a significant load, it will work rather poorly (hard to release) and is likely to have the pin assembly or the split ring fail.

Threaded shackle
The pin is threaded and one leg of the shackle is tapped. The pin may be captive, which means it is mated to the shackle, usually with a wire. The threads may gall if overtightened or have been corroding in salty air, so a liberal coating of lanolin or a heavy grease is not out of place on any and all threads. A shackle key or metal marlinspike are useful tools for loosening a tight nut.

For safety, it is common to mouse a threaded shackle to keep the pin from coming loose. This is done by looping mousing wire or a nylon zip tie through the hole in the pin and around the shackle body. For pins that have a cross-hole in the threaded end a cotter pin can be used. One disadvantage of wire is that mousing can introduce galvanic corrosion because of material differences; it is especially bad when used in places where the shackle is exposed to air and water. Nylon is not recommended for use where significant movement of the shackle is expected.

Twist shackle
A twist shackle is usually somewhat longer than the average, and features a 90° twist so the top of the loop is perpendicular to the pin. One of the uses for this shackle include attaching the jib halyard block to the mast, or the jib halyard to the sail, to reduce twist on the luff and allow the sail to set better.

Soft shackle
Modern strong fibers such as PBO (IUPAC name: poly(p-phenylene-2,6-benzobisoxazole), aramids (Kevlar,  Technora, Twaron), Vectran, carbon fibers, ultra-high-molecular-weight polyethylene (UHMWPE, Dyneema, Spectra) and other synthetic fibers are used to make extra strong ropes which can also be tied into lockable loops called soft shackles.

According to sailmagazine.com "a soft shackle can handle just about every function performed by a metal shackle, in many cases better. Soft shackles articulate better, don’t rattle around when not under load, don’t chew up toe rails or beat up masts and decks, don’t hurt when they whack you on the head, are easier to undo and don’t have pins that fall overboard at a critical moment". A modern rope can lift as heavy loads as a steel wire 3 times as thick and much heavier. Metal shackles may be preferred because soft shackles can be cut by sharp edges, burned, or deteriorate in some environments.

One disadvantage of soft shackles made of Dyneema and other modern fibers is their susceptibility to be weakened by heat, also heat caused by friction. It is advisable to subject it to medium level loads for a while to remove any slack that may cause friction heat when loaded to its maximum.

The stopping knot of a soft shackle may be a True lover's knot, a diamond knot, a double line celtic button knot or a chinese button knot (ABOK #600, ABOK #601, ABOK #603 doubled as one tail-end reverse-trails the other, emerging tail-ends preferably buried in the opposing main part as it emerges together from the knot for Chinese finger trap attachment). Another preferred stopping knot is a two rope combined wall+crown+wall+crown knot (a two string rose knot). The latter ones with the added thickness of the returning tail ends have the advantage of less of a sharp curvature at their weakest spot, the eye around the neck of the button.

title: Shackle