A Power Cable is an assembly of one or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed.
Early telegraph systems used the first forms of electrical cabling, transmitting tiny amounts of power. Gutta-percha insulation used on the first submarine cables was, however, unsuitable for building wiring use since it deteriorated rapidly when exposed to air.
Modern power cables come in a variety of sizes, materials, and types, each particularly adapted to its uses.[6] Large single insulated conductors are also sometimes called power cables in the industry.
Some power cables for outdoor overhead use may have no overall sheath. Other cables may have a plastic or metal sheath enclosing all the conductors. The materials for the sheath will be selected for resistance to water, oil, sunlight, underground conditions, chemical vapors, impact, or high temperatures. In nuclear industry applications the cable may have special requirements for ionizing radiation resistance. Cable materials may be specified not to produce large amounts of smoke if burned. Cables intended for underground use or direct burial in earth will have heavy plastic or metal, most often lead sheaths, or may require special direct-buried construction. When cables must run where exposed to mechanical impact damage, they may protected with flexible steel tape or wire armor, which may also be covered by a water resistant jacket.
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Using LED light source, the development prospect of micro projectors can be expected
As a true portable projection device, the pico projector has received more and more attention. At the 2008 CES show in the United States, prototypes of various pico projectors were exposed one by one and combined with various mobile portable devices such as PDAs and mobile phones to make projections ubiquitous.
At present, the micro projector uses DLP and LCoS technology. Due to its small size, it mainly uses LED as the light source. The brightness is between 50-150 lumens. The problem of low brightness is still improved. Generally, it can project 20-50. ? Curtain face. With the official debut of the micro projector at the end of the year, it is expected that in the next few years, the application of micro projection technology will become a new growth point in the projector market.
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