NCBI Bookshelf. Working safely with hazardous chemicals requires proper use of laboratory equipment. Maintenance and regular inspection of laboratory equipment are essential parts of this activity. Many of the accidents that occur in the laboratory can be attributed to improper use or maintenance of laboratory equipment. This chapter discusses prudent practices for handling equipment used frequently in laboratories. The most common equipment-related hazards in laboratories come from devices powered by electricity devices for work with compressed gases, and devices for high or low pressures and temperatures.
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Equipment Needed to Set Up a Simple Video StudioVIDEO ON THE TOPIC: Living Universe - Journey To Another Stars - Documentary 4K
The technology of television has evolved since its early days using a mechanical system invented by Paul Gottlieb Nipkow in Every television system works on the scanning principle first implemented in the rotating disk scanner of Nipkow. This turns a two-dimensional image into a time series of signals that represent the brightness and color of each resolvable element of the picture. By repeating a two-dimensional image quickly enough, the impression of motion can be transmitted as well.
For the receiving apparatus to reconstruct the image, synchronization information is included in the signal to allow proper placement of each line within the image and to identify when a complete image has been transmitted and a new image is to follow.
While mechanically-scanned systems were experimentally used, television as a mass medium was made practical by the development of electronic camera tubes and displays.
By the turn of the 20th century, it was technically feasible to replace the analog signals for television broadcasting with digital signals. Many television viewers no longer use an antenna to receive over-the-air broadcasts, instead relying on cable television systems.
Increasingly these are integrated with telephone and Internet services. The elements of a simple broadcast television system are:. Practical television systems include equipment for selecting different image sources, mixing images from several sources at once, insertion of pre-recorded video signals, synchronizing signals from many sources, and direct image generation by computer for such purposes as station identification.
The facility for housing such equipment, as well as providing space for stages, sets, offices, etc. Communication from the studio to the transmitter is accomplished via a dedicated cable or radio system. Television signals were originally transmitted exclusively via land-based transmitters. The quality of reception varied greatly, dependent in large part on the location and type of receiving antenna.
This led to the proliferation of large rooftop antennas to improve reception in the s, replacing set-top dipole or "rabbit ears" antennas, which however remained popular. Antenna rotors , set-top controlled servo motors to which the mast of the antenna is mounted, to enable rotating the antenna such that it points to the desired transmitter, would also become popular. In most cities today, cable television providers deliver signals over coaxial or fiber-optic cables for a fee.
Signals can also be delivered by radio from satellites in geosynchronous orbit and received by parabolic dish antennas , which are comparatively large for analog signals, but much smaller for digital. Like cable providers, satellite television providers also require a fee, often less than cable systems.
The affordability and convenience of digital satellite reception has led to the proliferation of small dish antennas outside many houses and apartments.
Digital systems may be inserted anywhere in the chain to provide better image transmission quality, reduction in transmission bandwidth , special effects, or security of transmission from reception by non-subscribers. A home today might have the choice of receiving analog or HDTV over the air, analog or digital cable with HDTV from a cable television company over coaxial cable , or even from the phone company over fiber optic lines. On the road, television can be received by pocket sized televisions, recorded on tape or digital media players, or played back on wireless phones mobile or "cell" phones over a high-speed or "broadband" internet connection.
Each has its pros and cons. Front projection and plasma displays have a wide viewing angle nearly degrees so they may be best for a home theater with a wide seating arrangement. Rear projection screens do not perform well in daylight or well-lit rooms and so are only suitable for darker viewing areas.
Display resolution is the number of pixels of one row on a given screen. Before the year horizontal lines of resolution was the standard method of measurement for analog video. For example, a VHS VCR might be described as having lines of resolution as measured across a circle circumscribed in the center of the screen approximately pixels edge-to-edge. With analog signals, the number of vertical lines and the frame rate are directly proportional to the bandwidth of the signal transmitted.
The higher the resolution on a specified display the sharper the image. Contrast ratio is a measurement of the range between the lightest and darkest points on the screen. The higher the contrast ratio, the better looking picture there is in terms of richness, deepness, and shadow detail. The brightness of a picture measures how vibrant and impacting the colors are.
On the other hand, the so-called brightness and contrast adjustment controls on televisions and monitors are traditionally used to control different aspects of the picture display. The brightness control shifts the black level, affecting the image intensity or brightness, while the contrast control adjusts the contrast range of the image.
There are various bands on which televisions operate depending upon the country. Lower frequencies do not have enough bandwidth available for television. These rates were chosen to minimize distortion of pictures that could be produced in analog receivers.
For a given frame rate, an analog signal with lines per frame would use less bandwidth than one with or lines per frame. Higher bandwidth makes receiver design more complicated, requires higher radio frequencies to be used, and may limit the number of channels that can be allocated in a given area; the same radio frequencies useful for television are also in high demand for other services such as aviation, land mobile radio, and mobile telephones.
Band II is used for FM radio transmissions. TV systems in most countries relay the video as an AM amplitude-modulation signal and the sound as an FM frequency-modulation signal. An exception is France , where the sound is AM. Aspect ratio refers to the ratio of the horizontal to vertical measurements of a television's picture.
Mechanically scanned television as first demonstrated by John Logie Baird in used a vertical aspect ratio, oriented for the head and shoulders of a single person in close-up. Most of the early electronic TV systems, from the mids onward, shared the same aspect ratio of which was chosen to match the Academy Ratio used in cinema films at the time.
This ratio was also square enough to be conveniently viewed on round cathode-ray tubes CRTs , which were all that could be produced given the manufacturing technology of the time. Today's CRT technology allows the manufacture of much wider tubes, and the flat-screen technologies which are becoming steadily more popular have no technical aspect ratio limitations at all.
The BBC 's television service used a more squarish ratio from to 3 April , when it too switched to a ratio. This did not present significant problems, as most sets at the time used round tubes which were easily adjusted to the ratio when the transmissions changed. In the early s, movie studios moved towards widescreen aspect ratios such as CinemaScope in an effort to distance their product from television.
Although this was initially just a gimmick , widescreen is still the format of choice today and aspect ratio movies are rare. Yet the various television systems were not originally designed to be compatible with film at all.
Traditional, narrow-screen movies are projected onto a television camera either so that the top of the screens line up to show facial features, or, for films with subtitles, the bottoms.
What this means is that filmed newspapers or long captions filling the screen for explanation are cut off at each end. Similarly, while the frame rate of sound films is 24 per second, the screen scanning rate of the NTSC is The switch to digital television systems has been used as an opportunity to change the standard television picture format from the old ratio of 1. This enables TV to get closer to the aspect ratio of modern widescreen movies , which range from 1.
There are two methods for transporting widescreen content, the most common of which uses what is called anamorphic widescreen format. This format is very similar to the technique used to fit a widescreen movie frame inside a 1. The image is compressed horizontally when recorded, then expanded again when played back.
Recently "widescreen" has spread from television to computing where both desktop and laptop computers are commonly equipped with widescreen displays. There are some complaints about distortions of movie picture ratio due to some DVD playback software not taking account of aspect ratios; but this may subside as the DVD playback software matures. Furthermore, computer and laptop widescreen displays are in the aspect ratio both physically in size and in pixel counts, and not in of consumer televisions, leading to further complexity.
This was a result of widescreen computer display engineers' assumption that people viewing content on their computer would prefer that an area of the screen be reserved for playback controls, subtitles or their Taskbar, as opposed to viewing content full-screen. The television industry's changing of aspect ratios is not without difficulties, and can present a considerable problem.
Displaying a widescreen aspect rectangular image on a conventional aspect square or display can be shown:. A conventional aspect square or image on a widescreen aspect rectangular with longer horizon display can be shown:. A common compromise is to shoot or create material at an aspect ratio of , and to lose some image at each side for presentation, and some image at top and bottom for presentation.
In recent years, the cinematographic process known as Super 35 championed by James Cameron has been used to film a number of major movies such as Titanic , Legally Blonde , Austin Powers , and Crouching Tiger, Hidden Dragon.
In North America, the basic signal standards since had been compatible enough in that even the oldest monochrome televisions could still receive color broadcasts. However, the United States Congress passed a law which required the cessation of all conventional television broadcast signals by February The digital channels occupy the same spectrum as the analog channels.
Some of the spectrum previously occupied by the highest numbered channels was auctioned off by the United States' Federal Communications Commission for other uses. PAL-M may have a similar decommissioning timeline. The European Union has recommended its members to close down analogue terrestrial television by Luxembourg and the Netherlands already completed their closedowns in , and Finland and Sweden closed down their analogue broadcasts in Britain started its digital switch in October The remaining four analogue channels ceased broadcasting shortly after.
The original five channels are now available only in digital form, alongside approximately 15 additional free-to-air channels.
In the early days of television, cabinets were made of wood grain often simulated particularly in the later years , however, they went out of style in the s. These were large about 6' wide by 4' high wooden cabinets containing a television, speakers, radio and a turntable. From Wikipedia, the free encyclopedia. This article has multiple issues. Please help improve it or discuss these issues on the talk page. Learn how and when to remove these template messages.
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An unreliable and wholly unofficial history. More, even, than a production company. The BBC was a national resource. It trained and produced the greatest technicians in television, most of whom then eventually went on to work in the film industry. It was a centre of learning and creativity, with an executive culture that trusted the creative staff to do their job. It was the place everyone wanted to work, despite the fact that you got more money on ITV.
Are you struggling to compete in a crowded online niche? Set-up a simple TV-video studio in your house or office and dazzle your fans with videos that show off your products or services. A studio allows you to create lots of videos quickly. Something to consider is that the quality of the videos will not be as high as if you were to go to a company like Mosaic Media Films — Austin Video Production.
Work Exempt from Building Permits
At the heart of any studio is the audio console sometimes called a radio panel, sound panel, or sound desk. The fader slider attenuates or amplifies the incoming signal. A microphone captures sounds from the studio and turn it into electrical impulses. Studio microphones are often mounted on a special arm that keeps the microphone at the correct height.
A television studio , also called a television production studio , is an installation room in which video productions take place, either for the recording of live television to video tape , or for the acquisition of raw footage for post-production. The design of a studio is similar to, and derived from, movie studios, with a few amendments for the special requirements of television production. A professional television studio generally has several rooms, which are kept separate for noise and practicality reasons. These rooms are connected via ' talkback ' or an intercom , and personnel will be divided among these workplaces. The studio floor is the actual stage on which the actions that will be recorded and viewed take place. A typical studio floor has the following characteristics and installations:. While a production is in progress, people composing a television crew work on the studio floor. The production control room is the place in a television studio in which the composition of the outgoing program takes place. The central apparatus room CAR houses equipment that is too noisy or runs too hot to be located in the production control room PCR. It also makes sure that coax cable , SDI cable , Fibre optic cable or other wire lengths and installation requirements keep within manageable lengths, since most high-quality wiring runs only between devices in this room.
Technology of television
A building permit is not required for the work described below; however, work exempt from a permit must still comply with applicable Building Codes, City Codes, and all other applicable ordinances. Applies to one- and two-family dwellings and townhouses not more than three stories:. Applies to Commercial Projects, including those with Residential occupancies not covered by the Residential Code:. Skip to main content.
Что мне следует делать. Взгляд Хилвара постепенно стал утрачивать отрешенное - Я все еще не понимаю, - сказал он, - но нет нужды бояться, в этом я уверен.
Твое тело не выдержит условий пустыни, где город больше не сможет защищать и оберегать. - Если выход из города существует, - медленно произнес Элвин, - что же помешает мне покинуть. - Это глупый вопрос, - сказал Джезерак. - Полагаю, ответ тебе уже известен. Джезерак был прав, но в ином, не предусмотренном им самим смысле. Элвин действительно уже знал - или, точнее, он догадался.
Ответ он получил от своих друзей: и в жизни, и в грезах, в приключениях, по ту сторону реальности, которые он разделял с. Они никогда не сумеют покинуть Диаспар; но Джезерак не подозревал, что принуждение, управлявшее их жизнями, не имело власти над Элвином.
Элвин не знал, является ли его уникальность делом случая или же результатом какого-то древнего плана; но так или иначе, данное свойство его сознания было следствием именно этой уникальности.
Для него -. Да, он не сомневался, что и за тысячу жизней не исчерпать всех чудес города, не испробовать всех возможных путей бытия. Он мог бы заняться этим, но никогда не получит удовлетворения, пока не совершит нечто более значительное. Оставался лишь один вопрос: что же именно следует Этот вопрос без ответа вывел его из состояния дремотной мечты. В таком беспокойном настроении он, однако, не мог оставаться дома.
Для пробы Олвин подал ему команду, и огромный экран, затрепетав, ожил. Перед ним появилась башня Лоранна, странным образом укороченная и даже, судя по всему, лежащая на боку. Еще несколько команд -- и он увидел небо, город и бескрайнее пространство пустыни. Четкость изображения была безупречна, почти ненатурально хороша, хотя, казалось, никакого увеличения н не.
Олвин поэкспериментировал еще некоторое время, пока не наловчился получать именно то изображение, которое ему хотелось бы увидеть. И теперь он готов был -- Перенеси меня в Лиз. -- Это, конечно, была команда из простых, но как мог корабль повиноваться ей, если он и сам не имел ни малейшего представления о том, в каком именно направлении лететь. Олвин сначала просто не подумал об этом, а когда сообразил, то корабль уже мчался над пустыней на головокружительной скорости. Олвин пожал плечами, с благодарностью принимая то обстоятельство, что теперь в его распоряжении находится слуга куда более знающий, чем он.
Определить масштаб изображения, которое скользило сейчас по экрану, было нелегко, но, судя по всему, ежеминутно они, должно быть, покрывали пространство во много миль.
На их место заступали новые воспоминания, ложные, хотя и тщательно спланированные, и его личность до поры поступала на хранение в схемы города. И вот наступил момент, когда в Диаспаре не осталось ни одного живого человека; в нем был лишь только Центральный Компьютер, подчинявшийся приказам, заложенным в него нами, и управлявший Банками Памяти, в которых мы спали.
Не осталось никого, кто имел бы связь с прошлым - и вот с этой точки и началась наша история. Тогда, один за другим, в предопределенном порядке, мы были призваны из схем памяти и вновь облечены плотью.
Было ясно, что существо имеет неземное происхождение. Но Хилвару, несмотря на немалые познания в биологии, понадобилось время, чтобы сообразить, с каким именно организмом они имеют.
Это было не единое существо; в разговоре оно всегда называло себя "мы".
Те, кто все еще цеплялся за свои иллюзии и пытался найти убежище в будущем, напрасно входили теперь в Зал Творения. Растворяющее холодное пламя больше не приветствовало их. Им уже не суждено было снова проснуться спустя сотню тысяч лет ниже по реке Времени. Обращаться к Центральному Компьютеру тоже было без толку, да он и никогда-то не объяснял своих действий.
Уже самый первый взгляд на лица членов Совета подсказал Олвину, каково их решение, Он не был ни удивлен, ни особенно разочарован и не выказал никаких чувств, которые могли бы ожидать от него советники, когда слушал, как председатель подводит итоги обсуждения.
-- Мы всесторонне рассмотрели ситуацию, которая порождена твоим открытием, Олвин, -- начал председатель, -- и пришли к следующему единогласному решению.
Поскольку никто не желает каких-либо изменений в нашем образе жизни и поскольку только раз в несколько миллионов лет рождается кто-то, кто способен покинуть Диаспар, даже если средства к этому существуют для каждого из нас, то туннельная система, ведущая в Лиз, не является необходимой и, очень возможно, даже опасна.